Title of Invention

"DENTAL CARE HERBAL FORMULATION AND ITS PREPARATION THEREOF"

Abstract

DENTAL CARE HERBAL FORMULATION AND ITS PREPARATION THEREOF. The present invention relates to a synergistic dental care herbal formulation and its process of preparation comprising an active fraction from Azadirachta indica designated as Fraction A and a fraction from Citrullus colocynthis designated as Fraction B, along with a fraction C containing an antioxidant from Cucumis sativus extract; and pharmaceutically accepted a carrier wherein the ratio of the components ranging between about 2 to 5.5% of fraction A; about 0.5 to 2.5% of fraction B; about 0.1 to 0.4% of extract of Cucumis sativus; and about 82 to 97% of carrier or additive.

Full Text

Field of the Invention The present invention relates to a dental care herbal formulation, its preparation, and its application for control of dental plaque and gingivitis, comprises a combination of active fractions from Citrullus colocynthis and neem. The invention includes a process to extract active constituent of neem bark and leaves as component A, underground plant parts of Citrullus colocynthis as component B, and an antioxidant fraction from Cucumis sativus as component C. The invention includes an alternative and effective method of extraction of neem leaf and bark by super critical fluid extraction using CO2 as carrier gas for extraction; and further partitioning by liquid phase extraction using a polar and non polar solvent; polar fraction containing nimbolides rich concentrate as component A. The invention includes a process combining component A, from neem leaf and bark that comprising primarily nimbolides (2 to 5.5 %); component B from Citrullus colocynthis, comprising primarily glycosides (0.5 to 2.5 %); addition of 0.1 to 0.4 % of antioxidant fraction from component C. Component C has been added to Component A and B to provide anti-oxidant properties and stability. The objective is to provide recipe to develop dental care formulation combining root of Citrullus colocynthis; leaf and bark of neem with an addition of antioxidant fraction from fruits of Cucumis sativus. Background of Invention Herbal medicines or herbal drugs are of ancient origin and their use is known in cultures throughout the world. In India science of herbal medicine known as "ayurveda" medicine, which gives us the modem term "ayurvedic," derived from "ayur," meaning life and "veda" meaning knowledge. A movement to identify individual active ingredients in beneficial herbs developed in the 18th century, leading into a transitional period from the use of natural herbs to the use of pharmaceutical drugs such as extracts and purified chemicals, sometimes referred to as allopathic drugs. With advances in chemistry, some of the active ingredients were chemically synthesized and given to patients in the form of pills. However, during this time of transition, the synthesized, purified or extracted active ingredients of pharmaceutical drugs were observed to exhibit significant adverse side effects. Generally, herbal medicines do not produce significant side effects, perhaps because the active ingredients are combined with other compounds in the herb and administered in different dosages. In addition, herbs often are administered in combinations, which may nullify the side effect of any one herb. However, purified pharmaceutical drugs seldom are administered in combinations to offset each other's side effects, perhaps because even the offsetting drug is likely to produce its own side effects. It appears that modern medical practice accepts the presence of side effects as an adjunct to the improved purity and efficacy of pharmaceutical drugs. Modern drug synthesis has the advantages of providing pure and potent drugs in large quantities and with considerable speed for wide availability. However, the accompanying problem of side effects is gaining increased notice as the public justly criticizes that such pure and potent drugs can cure one ailment while causing another. Several plants species are known to have helped in cure, treatment of periodontal diseases, particularly in alleviation of tooth aches. In the literature, several plants have been referred to as commonly used plants for dental care. In recent years, on account of adverse effects of synthetic drugs, attempts have been made upon the potentially of phytochemicals for the prevention and treatment of periodontal diseases. Various plant preparations like Azadirachta indica (1), Acacia (2), Oolong tea (3), Juglans regia (4, 5), Zanthoxylum alantum (5), Mimusops elengi (5) and Hibiscus abelmoschus (5) etc. have been used for the prevention of periodontal diseases. There have been several reviews on neem, however most of these relate to its pesticidal properties (6-8). Almost every part of the tree has long been used in traditional folklore medicines for the treatments of a variety of human ailments, particularly against diseases of bacterial and fungal origin. Antibacterial and antifungal (9) anti-malarial (10, 11), antipyretic and anti-inflammatory (12) are the most frequently cited uses of neem. Andrew et al. (13) reported that neem is a part of Ayurvedic and folk medicine in India and has a potential for several remedies. Gahukar (14) reported use of neem twigs for pyorrhoea infection. Wolinsky et al (15) investigated bactericidal properties of neem extract. Their studies with aqueous extracts revealed that bacterial properties are altered and ability of Streptococci to colonize tooth surface are inhibited. Farooqi et al. (16) reported that Azadirachta indica stem are used as chewing sticks. Guhabakshi et al. (17) reported that different parts of neem (Azadirachta indica) such as young branches are used as tooth brush, particularly in pyorrhoea; decoction of leaves for washing septic wounds etc. African members of the Meliaceae such as the Crabwood or Monkey Cola Tree {Carapa procera) and Dry Zone Mahogany (Khaya senegalensis) are also used as chewing-sticks, and like neem are used to heal (particularly skin and oral infections) and treat malaria (18,19). Effect of chewing sticks of neem on dental health has been attributed to presence of fluorides in plants parts. Chawala (20) reported that 20 % w/v aqueous extracts of a neem chewing-stick (presence of bark unknown) yielded 2.8 ppm fluoride. Presence of fluoride has been reported to prevent accumulation of bacteria on teeth. Chewing sticks of Azadirachta indica and Salvadora persica ("Miswak") were tested for their antimicrobial activity using various concentrations. Both the chewing sticks were affective against Streptococcus mutans and S. faecalis (21) Arak extract was more effective at lower concentrations against S. faecalis. This difference was attributed to the difference in their pH values. Neem bark contains tannins and 8 to 11 percent of anti-inflammatory polysaccharides (Terumo Corporation US patent # 4,515,785). These polysaccharides contain glucose, arabinose and fructose in an approximate ratio of 1:1:1. Apart from these several diterpenoids (Nimbosodione; Nimbisonol; Demethyl Nimbiolon; Margosone; Margosolone; Nimbonone; Nimbonolone; Nimbionone; Nimbionol; Nimbione; Nimbinone and C-seco tetranortriterpenoids iso-nimbionlide) have also been reported. Masaki Shimizu et al (22) patented a process to extract neem bark using solvents like benzene and toluene etc. The extract was found to retard growth of sarcoma tumours in mice. However later they extended the patent by reporting extraction in alcohol after treating bark with water at 0 to 40 C. In 1966 there were only three known triterpenoids from neem. Studies of Jarvis and Morgan (23) on the antifeedant properties in neem seeds led to azadirachtin stimulated research, so that many other compounds were isolated in the 1970's and 1980's from neem (24). Today there are more than 145 known neem triterpenoids, and there must be others yet to be discovered. Little more than one third of these have been tested for biological properties. Many of these triterpenoids (25, 26) have been isolated from neem oil. Four neem iimonoids: gedunin, dihydrogedunin nimbinin, and nimbolide reportedly possess LC5o values of 0.72 to 1.74 ng/ml against P. falciparum in vitro (27). Some rural communities in Kenya are already using neem for alternate preventive and curative treatment against malaria. A survey of communities in Western Kenya, bordering Lake Victoria, revealed that 98 % members of the communities knew about neem; 36 % had actually used neem for malaria prevention and treatment (28). They got relief by using bark or leaves boiled in water; some used seed powder dissolved in warm water, or a mixture of neem leaves, bark, and roots boiled in water. These preparations were administered at 1 to 2 glasses twice or thrice a day until recovery as few chewed neem leaves several times a day; other inhaled neem leaf smoke thrice a day. Use of neem oil is becoming popular for treating ringworm (Tinea species) among children in rural Kenya (29). Application of a paste made from neem leaves and turmeric in 4:1 proportion to the skin reportedly cured 97 % of the patients suffering from scabies caused by the itch mite, Sarcoptes scabei in 3-15 d (30). In Kenya, severe cases of scabies in children are getting cured by bathing with water from boiled leaves and then applying neem oil on affected body parts (29). Voorhees J. & Nachman L. used 5 to 10 % neem leaf powder along with 80 to 88 % olive leaf extract and homeopathic blend for preparing a composition for treating symptoms of influenza (US Patent # 20,020,110,600). Wolf et al. (US Patent # 6,228,402) have reported a Xylitol containing non-human food stuff for a treatment for reducing the incidence of dental carries in animals (31). They have (not as a claim) but as a suggestion reported that other ingredients including neem oil can be used. U.S. Ser. No. 07/456,762 and 5,298,251 (Locke et al.) teaches that non-polar hydrophobic solvent extracts of ground neem seed yield a neem oil product that can have combined insecticidal and fungicidal activities. They reported that clarified neem oil demonstrates increased insect repellence, decreased phyto-toxicity, decreased skin irritability, increased fungicidal activity and increased wetting ability. The neem wax demonstrates increased insect repellence, increased fungicidal activity and increased wetting ability (32). There have been several other patents on neem but these are primarily on use of neem as pesticide or neem based pesticidal stable formulations such as US Patents # 04,556,562 (Stable anti-pest neem seed extract; # 4,902,713 (azadirachtin like compound and insect destroyed agents); # 4,943,434 (insecticidal hydrogenated neem extract); # 4,946,681 (method to prepare in improved storage stable neem seed extract); # 4,960,791 (salanin derivation insect control agents); # 5,001,146 (storage stable azadirachtin formulation); # 5,001,149 (azadirachtin derivative insecticides); # 5,047,242 ( azadirachtin derivative insecticides); # 5,110,591 (neem oil emulsifier); # 5,124,49 (storage stable azadirachtin formulations); # 0,436,257 B1 (method of controlling fungi on plants by the aid of hydrophobic extracted neem oil) etc. Citrullus colocynthis Schrad., a member of family Cucurbitaceae, commonly known as "indrayan", "tumba", "Ghorumba", "kaur-tumba", " tumba", " tumbi" or bitter apple is a wild plant. It has also been referred by its earlier name Citrullus vulgaris. Colocynth is most abundant in north-western plains of India, especially in the Barmer, Bikaner, Jaisalmer and Jodhpur districts of Rajasthan, and in Gujarat where it forms large patches on sand dunes, sandy undulating plains and inter-dunal areas; occurs wild throughout India particularly in the North-west, Central ad South India and on the sea shores of the Coromandal coast, Gujarat, and other parts of Western India. In recent years colocynth has found a place in the oil industry of western Rajasthan. Thus, its cultivation in Rajasthan serves three purposes, viz. continuous supply of seed (as cash crop) to oil industry for soap-making; stabilization of shifting sand, and checking the danger of its becoming extinct due to over exploitation. The fruits and seeds are occasionally used as food in parts of Africa. The gourds are eaten after pickling which makes them safe for eating. They are made into preserves after boiling thoroughly in water to remove their bitterness. They are also used as vegetable after removing their rind. The stem and leaves are eaten by goats and wild game (33-36). Its fruits and seeds have purgative properties, while roots are used as purgative, used in ascites, jaundice, urinary diseases and rheumatism, these are also used as antid and against snake poison. The bitter substance has been reported to be colocynthin and colocynthetin (Amer. J. Pharm., 1893, 179; Pharm. J., 1907, 117; Arch. Harm., Berl., 1883, 201; J. Chem.. Soc, 1910, 99; Indian J. med. Res., 1929, 770); roots contain alpha-elaterin, hentria-contane, and saponins (Curr. Sci., 1934, 350); seeds contain fixed oil, a phytosterolin, phytosterols, hydroxyl carbons, saponins, glycosides and tannin (J. Indian chem. Soc, 1949, 515, 519); pulp contains alpha-elaterin, hentriacontane, a phytosterol and a mixture of fatty acids (B.P.C. 1934, 348) (37-41). Okieimen et al. (42) reported removal of heavy ions from aqueous solution with melon (Citrullus vulgaris) seed husks (Biological Wastes:0269, 7483, 1989). Citrullus vulgaris Schrad has been proposed as an effective feeding stimulant (US Patent # 5,968,541). Citrullus colocynthis has been used, as a powder, to impart bitter flavour to the composition for topical animal medication such as to prevent common house pets such as dogs and cats from licking their wounds. The claim made in the patent is for use only as a bittering agent (US Patent # 6,274,555). Citrullus colocynthis contains several bitter principals; cucurbitacin is one of the major ones present in several genera of the family Cucurbitaceae. The cucurbitacin are a group of bitter-tasting, highly oxygenated, mainly tetra cyclic, triterpenic plant substances derived from the cucurbitane skeleton (43). These compounds are present in many plants and function as an allomone to protect the plants from herbivores (44). In addition, the cucurbitacins are known to have purgative, anti-inflammatory, anti-fungal, and anti-cancer properties (45); anticancer agents based on natural product models (46) Commercialization of cucurbitacin-based products has been very limited because (a) the triterpenes are secreted in very small quantities in cucurbitaceous plants, and (b) the existing procedures involved in obtaining pure cucurbitacin is lengthy and burdensome (47). The difficulties involved in obtaining large quantities of cucurbitacins in the past have discouraged serious pursuit of most potential uses of this triterpenes. McMahon et al. (48) taught controlled-release microcapsules that contain insecticides and other compounds useful in crop management. In one embodiment of the invention, the capsule wall contains an anti-feedant compound comprising cucurbitacin-containing solid particles, powder or dust (48). The preferred cucurbitacin-containing solids used are in the form of dried, ground, gourd roots as described in U.S. Patent # 4,880,624. Branly et al. (49) describes baits for diabroticite beetles containing a feeding stimulant and an insecticide. The feeding stimulant comprises plant tissue containing cucurbitacin, and more specifically comprises dried buffalo gourd root in an amount of 10-100 lb. of ground root per acre. Based on this technology, a cucurbitacin-dependent control method for adult cucumber beetles has reportedly been developed. By lacing cucurbitacin-containing plant tissue with insecticide, the beetles are "tricked" by the feeding-stimulant cucurbitacin into eating the toxins. Ground root tissue containing cucurbitacin has been used as broadcasted bait capable of killing 99 % of the diabroticite beetles consuming it (47, 50). However, it is reported that this form of cucurbitacin is effective in the control of adult beetles only, while much of the damage caused by the diabroticite beetles is caused by the larval form (51). The use of purified cucurbitacins in place of plant tissue is one possible solution to this problem, as purified cucurbitacin has been shown to be an effective feeding stimulant for diabroticite beetles in both adult and larval forms. Unfortunately, there are no products marketed today that utilize purified cucurbitacin. Berdami; L. A. (52) developed a composition and method for topical animal medication consisting of bacitracin zinc, neomycin, polymycin-B sulfate, and pramoxine hydrochiomide. They used Citrullus colocynthis as a bittering agent to impart a bitter flavor to the composition such as to prevent common house pets, such as dogs or cats, from licking their wounds. Subbiah, V. (53) describes a method of isolating and purifying cucurbitacins from Cucurbita species (not Citrullus colocynthis). Most of the earlier studies on application of cucurbitacin are from Cucurbita speciea and not Citrullus colocynthis. However, Hatam et el (54) have isolated cucurbitacin glycosides from Citrultus colocynthis. Main diseases of the teeth include plaque, carries and pyorrhoea. Dental plaque is the main cause of most of the periodontal diseases (55, 56). Plaque control is the only effective method of controlling chronic periodontal diseases. People use mechanical devices to control plaque. These are tooth brush used with tooth paste, abrasive powders, inter-dental cleaning aids, oral irrigation devices etc. However, these practices have several limitations and the entire tooth surface cannot be cleaned. Moreover, once plaque is deposited in substantial quantities, it is difficult to remove with common mechanical methods. Once plaque is deposited, this leads to other diseases. These mechanical aids are not therapeutic in activity; hence chemotherapeutic agents remain in demand for periodontal diseases. Prominent among the chemicals used are antibiotics (57), enzymes (58), dextrose (59), chlorhexidine (60), urea peroxide (61), organic and inorganic fluorides (62) and ammonium compounds (63) etc. Many of these products are effective to some extent but either are limited in their use or have side effects. Earlier several plant species have been used for dental care. Some of plants used as dental care are. Acacia catechu TABLE 1 (Table Removed) These plants have been reported as effective anti-plaque inhibitors without any side effects. Some of the herbal extracts especially neem in "in vitro" studies have also shown inhibition of Staphylococcus aureus, Streptococcus pyogens and anaerobes. These "in vitro" studies support the anti plaque potentiality of neem. Neem has been used as a component of toothpastes, mouthwashes, food compositions gingivitis, for reducing caries and treatment of inflammation of the mouth, as a natural flavoring agent in oral compositions used for treating plaque and gingivitis (64-66). It has also been used as a component of Chewing gum containing a teeth whitening agent (67) Ahmad, et al. (68) used micro-sized particles or microfibers of branches or roots of plants named by them as Azadirachta or Salvadora persica, and commonly known in different parts of the world as the peelu, miswaak, neem or siwak tree. They used these particles in place of commonly used mineral abrasives. Scheller (69) in his patent (US Patent # 4,223,003) used neem oil as one of the optional components of their paste and powder dentifrices. Miller S. E. and Simone A. J. reported formulation of chewing sticks made from natural fibbers. They suggested use of neem oil but no claim to its properties was made. Also no description of extraction of oil or plant parts used was given (70). Nabi et al (71) reported a formulation comprising thymol and eugenol, and optionally a sesquiterpene alcohol. They claimed the formulation to have plaque and gingivitis effects. They suggested use of neem oil to provide an organoleptically acceptable oral product. Seabrook, Jr. et al. suggested use of neem seed, leaf, bark extracts and oil in their formulations of polymers containing antimicrobial agents. They suggested that the antimicrobial agents include phytochemicals and phyto-nutrients such as naturally occurring extracts from plants and herbs and other chemical disinfectants (72). At present, a number of tooth powders which contain cheap pulverized items that are not very effective as well as harmful for gums and teeth and have toxic effects are available in India. Compositions of some of the herbal tooth powders as available in market are given below: (Table Removed) Critical review of earlier patents/prior art > Data related to clinic value of neem used as chewing sticks are rare and only in generic forms. > Formulations are crudely prepared as aqueous solutions, chewing sticks, or leaf and bark extracts. > Claims are made of effect of azadirachtin (from neem) in formulations; azadirachtins have been reported to have insect antifeedant and repellent properties and there are no claims for dental protection. > Some of the commercial dental care formulations suffer from a number of disadvantages. Some stain teeth and gums. Most of these products lack standardization. > No prior art of use of Citrullus colocynthis for dental cure, alone or in combination of Azadirachta indica > Majority of patents and formulations (quoted in the text) are on pesticidal activities for filed crop of neem. > Berdami; L. A. (US Patent # 6,274,555) used Citrullus colocynthis as a bittering agent in their composition for topical animal medication. They used a few grains of Citrullus colocynthis as a bittering agent to impart a bitter flavor to the composition such as to prevent common house pets, such as dogs or cats, from licking their wounds. No claim with respect to cure for plaque or gingivitis was made. Moreover they did not use roots of Citrullus colocynthis. > Cucurbitacins from Citrullus like plants has been used as in U.S Patent # 5,466,460 as an antifeedant compound in the walls of capsules containing targeted insecticide. The use thus is only as an antifeedant. > Locke et al. (US Patent # 5,298,251 and U.S. Ser. No. 07/456,762) reported a fungicidal composition derived from neem oil and neem wax fractions. However they did not use neem leaves and bark and no claim to therapeutical use against dental plaque or gingivitis was made. > Seabrook, Jr. et al. (US Patent # 5,906,825) suggested use of neem seed, leaf, bark extracts and oil in their formulations of polymers containing antimicrobial agents. They claimed their use as antimicrobial agents, however, neem was suggested as one of several agents; moreover this was only a suggestion and not a component of the claims of the patent. They also did not describe the extraction procedure and no claim or mention of anti-plaque or anti-gingivitis was made. > US patent # 4,515,785 and 4,537,774 by Masaki Shimizu et al (20) where they reported a procedure to extract neem bark using solvents like benzene and toluene etc. (the extract was found to retard growth of sarcoma tumours in mice) and later extended the same by reporting extraction in alcohol after treating bark with water at 0 to 40 C for higher purity does not incorporate cold extraction; or any combination with leaves or any other plant. They have also no claim on dental formulations. Their claim is on anti-tumour properties on sarcoma tumours in mice. US patent # 6,264,926 by Farooqi et al. (16) reported a synergistic composition comprising the pastes or powders of Zanthoxylum armatum, Zingiber officinale, Sandalwood, Roasted alum, Common salt, Spilanthes calva, Pistacia sp., Quercus infectoria, Usnea longisima in the proportion of 20-25 %, 25-30 %, 8.25-8.5 %, 8-9 %, 15-16 %, 2-2.5 %, 2-2.5 %, 8-8.5 %, and 1-4 % respectively. They did not use either Azadirachta indica or Citrullus colocynthis in their formulation. Howard H. S. has used (42 x) neem oil in chewing gum containing a teeth whitening agent. The neem oil as described in their patent has been taken from neem seeds (not from leaves and bark). Moreover the oil has been extracted using hexane from neem seeds and not leaves and bark. Also they have made no claims to its therapeutical use. Others such as Lewis W. H. (63); Maurice M. I. (64) and US Patents # 5,371,254; 5,472,684 and HI 541 have reported its utility for gum diseases yet no details of the proportions to be used, methods of extraction and any synergistic effects with other plants have been detailed. Ahmad, et al. (1991) in their patent # 5,009,886 on Dentifrice used micro-sized particles or microfibers of Azadirachta indica or Salvadora. It is not clear if they are botanically correct in naming the plants since they have named neem, peelu, miswaak or siwak as synonyms. In the detailed description they have mentioned only pilu which is botanically Salvadora persica. Moreover they have used wood for preparing abrasive in their dentifrice. Schellerin his patent on paste and powder dentifrices (US Patent # 4,223,003) used neem oil as one of the optional components, however no claim has been made on the benefit they derived by using neem oil. Moreover they have used neem oil apparently derived from neem seeds and not leaves and bark. Nabi et al. in their US Patent # 4,223,003 reported a formulation comprising thymol and eugenol, and optionally a sesquiterpene alcohol. They claimed the formulation to have plaque and gingivitis effects. The used neem oil as a flavouring agent, however it was only one the agents selected from the group consisting of, Tulsi oil, Neem oil, Eichinacea tincture, rosemary extracts, golden seed extracts, passion flower extract, turmeric extracts, betel nut extracts, sunphenon tea extracts, and dandelion root extracts. Neem oil was used only as a flavouring agent. No details of preparation of neem oil have been given; apparently it was oil extracted from seeds and not leaves and bark. > Wolf et al. (US Patent # 5,989,604 and 6,159,508) suggested use of neem oil in their xylitol based formulation for dogs (non-human animals) for reducing the incidence of dental carries. The invention is based on Xylitol, however as a suggestion they have listed several plants such as gum arabic, beef broth, chicken broth or distilled water, lecithin, Coenzyme Q10, folic acid, aloe vera, comfrey, rosemary, goldenseal, horsetail, arnica, calendula, barley grass, chamomile, bloodroot, siwak-miswak, pullulan, horse chestnut, neem, peelu, propolis, green tea, myrrh, birch bark, white oak bark, tea tree oil, grape seed extract, wheat germ, bromelain, papain and quercetincan be added to promote health of hard and soft dental tissue. There was no claim of the inventors as to use of neem as a cure or protection against dental plaque or gingivitis. This was only suggested as one of the several options to promote health of tissue when added to Xylitol. No method of extraction or details of the plant parts used has been given. > Wolf et al. (US Patent # 6,228,402) have reported a xylitol containing non-human food stuff for a treatment for reducing the incidence of dental carries in animals. They have as a suggestion added that other ingredients such as XXX can be added to promote health of hard and soft dental tissue. There was no claim of the inventors as to use of neem as a cure or protection against dental plaque or gingivitis. This was only suggested as one of the several options to promote health of tissue. OBJECTS OF THE INVENTION ■ The main objective of the present invention is to provide a synergistic herbal formulation useful for periodontal diseases, preventing dental plaque and gingivitis. ■ Another objective is to provide a formulation with no side effects, and free them from any toxicity or toxic residue and irritation when regularly used and which can give effective protection to teeth. It should be cosmetically acceptable and should not leave stain on teeth or fingers after use. ■ Yet another objective of the present invention is to provide a formulation which contains natural and medicinal plants useful for gums and teeth, which are safe, nontoxic and biodegradable. SUMMARY OF THE INVENTION The invention relates to a synergistic dental care herbal formulation comprising of fractions containing active constituents from neem (Azadirachta indica), Citrullus colocynthis and a fraction with antioxidants from Cucumis sativus. The invention including a process to combine component A from neem bark and leaf fraction rich in nimbolides; component B from underground part preferably root of Citrullus colocynthis comprising primarily glycosides; addition of 0.1 to 0.4 % of fraction rich in antioxidants from Cucumis sativus as component C and a carrier 5-18 % edible grade ethanol. The herbal formulation is useful for preventing and control of dental plaque and gingivitis applying on teeth and gums over a period of two weeks or more. The invention providing herbal formulation is non-toxic and biodegradable, suppressing growth of wide spectrum of micro organisms causing periodontal diseases; and useful in the form of lotion, cream, mouthwash, mouth rinse, toothpaste or similar forms of application in daily life or therapeutical application etc. The invention includes a process to extracting active constituent (primarily nimbolides) from neem bark and leaf, primarily glycosides from roots of Citrullus colocynthis using a polar solvent and non-polar solvent. It includes a process to purify active constituents from the above said fractions by partitioning through liquid phase extraction using a polar and a non polar solvent to obtain desired fractions from neem and Citrullus colocynthis as component A and B, respectively. In a preferred embodiment of invention, an alternative and effective method of extraction of neem bark and leaf by Super Critical Fluid Extraction using CO2 as carrier gas for extraction; and further partitioning by liquid phase extraction using a polar and a non-polar solvent; polar fraction with enriched nimbolides as active constituent (component A). The invention further includes a process to extract and combine an antioxidant fraction from Cucumis sativus by cold extraction using aqueous polar solvents at temperature around 20° C using tissue homogenizer; concentration of the filtrate provides stabilization to the formulation as component C. The invention includes, active constituents derived from herbal sources and are thus safe ecofriendly, biodegradable and have no toxicity and side effects. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1: Dental plaque before application of formulation showing plaque formation on teeth (example from a clinical trail). Figure 2 Controlled dental plaque after application of formulation (example from a clinical trail). Figure 3: Demonstration of antibacterial activity of "active fraction A", "active fraction B" and "combination of fraction A and B". DETAILED DESCRIPTION OF THE INVENTION The invention provides a synergistic herbal formulation comprising active fractions from neem (Azadirachta indica) and from Citrullus colocynthis, along with antioxidant rich fraction from Cucumis sativus and a carrier in the ratio ranging between about 2 to 5.5 % of neem, 0.5 to 2.5 % of Citrullus colocynthis, and 0.1 to 0.4 % of Cucumis sativus apart from 82-97 % of carrier or additive. In an embodiment, the invention further provides a herbal formulation from the plant part used is selected from fruits or roots of Citrullus colocynthis and bark and leaves (0.5-2.5 to 2-5.5) of neem, respectively. The invention includes an antioxidant from fruit peels of Cucumis sativus in the ratio ranging from about 0.1-0.4 %, and a carrier using 82-97 % aqueous edible grade ethanol. The above said herbal formulation is useful for application on teeth and gums as mouthwash, applying on teeth and gums with the help of cotton pellets twice daily for two weeks. The invention includes, a dental care herbal formulation is useful for preventing dental plaque and gingivitis in humans, and useful as antimicrobial agents for preventing periodontal diseases. The herbal formulation reduces >61 % dental plaque; >60 % in vitro bacterial colony forming units (CFU); >25 % gingivitis over a period of 2 weeks, showing no any cytotoxicity at concentration as proposed in the present invention and is useful in the form of lotion, cream, mouthwash and mouth rinse etc. The invention providing a process for preparation of formulation comprising about 2 to 5.5 % neem; about 0.5 to 2.5 % Citrullus colocynthis; about 0.1-0.4 % of Cucumis sativus; and about 82-97 % of carrier or additive. Extracting neem bark and leaves using commercial blender at a temperature of 10-25°C, preferably at about 20°C and in an aqueous solution of polar solvents, exclusion of tannins by liquid phase extraction using a non-polar organic solvent and a polar solvent; further concentrating and partitioning the above fraction by liquid phase extraction using a polar and a non-polar solvent and obtaining nimbolides rich fraction from neem as component A. Extracting underground parts preferably roots of Citrullus colocynthis, using a homogenizer at 7000 to 8000 revolution per minute in an aqueous polar solvent, purifying active constituents by concentrating and partitioning through liquid phase extraction using a polar and a non-polar solvent to obtain polar phase resulting in glycosides rich fraction as component B. The invention includes a process of extracting an anti-oxidant fraction from a plant source, preferably, Cucumis sativus by cold extraction using aqueous polar solvents at temperature ranging from 10-25°C using a tissue homogenizer, to obtain the polar fraction as component C. The invention further providing a process of mixing component A from neem, component B from Citrullus colocynthis, component C from Cucumis sativus, a carrier in a ratio ranging from 2 to 5.5 %, 0.5-2.5 %, 0.1-0.4 %, 82-97 %, respectively to obtain a herbal synergistic dental care formulation. (Table Removed) The invention providing an alternative and effective method of extraction of neem bark and leaf by super critical fluid extraction using CO2 as carrier gas for extraction; and further portioning by liquid phase extraction using a polar and a nonpolar solvent, polar fraction resulting in nimbolides rich fraction as component A. The polar solvent used is selected from the group consisting of methanol, ethanol, acetone, water; the non-polar solvents used is selected from the group consisting of hexane, chlorohexane, petroleum ether, chloroform, ethyl acetate, pyridine. The present invention is more fully illustrated by the following examples, which are set forth to illustrate the present invention and are not to be construed as limiting thereof. EXAMPLE 1: Extracting neem bark and leaves using commercial blender at a temperature of 10-25°C, preferably at about 20°C and in an aqueous polar solvent, exclusion of tannins by liquid phase extraction using a non-polar organic solvent and a polar solvent; concentrating and partitioning the above extract obtained from earlier step by liquid phase extraction using a polar and a non-polar solvent and obtaining polar fraction comprising rich in nimbolides as component A. Extracting plant parts of Citrullus colocynthis, preferably underground parts using a homogenizer at 7000 to 8000 revolution per minute in an aqueous polar solvent; purifying active constituents from extract by concentrating and partitioning through liquid phase extraction using a polar and a non-polar solvent to obtain polar phase as component B. Further analyzing the active fraction using Semi-Prep and Analytical HPLC. Analyses were performed on a Waters liquid chromatograph equipped with a automated gradient controller, a solvent delivery system, a sample injector fitted with a 20 (j,L loop, a photo diode array (PDA) detector. A nBondapakTM semi-prep and a yBondapak C18 analytical columns used for analysis. Mobile phase consisted of an isocratic mixture of acetonitrile-water at a flow rate of 1.5 ml_ min"1. Extracting anti-oxidant fraction from a plant source, preferably, Cucumis sativus by cold extraction using aqueous polar solvents at temperature ranging from 10-25°C using a tissue homogenizer, to obtain the polar fraction as component C. Mixing component A from neem comprising about 2 to 5.5 %, component B from Citrullus colocynthis about 0.5 to 2.5 %; component C from Cucumis sativus about 0.1 to 0.4 %; and about 82-97 % of carrier or additive to obtain a herbal synergistic dental care formulation. One kilogram of dry powder neem bark and leaf (in the proportion of 7:3) yielding 20.5 g of "active fraction A"; one kilogram of dry powder of Citrullus colocynthis root yielding 88 g of "active fraction B". The active fraction A from neem, and active fraction B from Citrullus colocynthis and an antioxidant fraction C from Cucumis sativus mixed to prepare the final formulation in aqueous ethanol. EXAMPLE 2: In another example of the invention, neem leaf and bark were extracted using Super Critical Fluid Extraction technique to isolate active metabolites. This technique is preferred over the earlier reported in Example 1 since the technique involves use of only CO2 as a carrier (extraction) gas and no solvent is sued. It renders the final extraction product very eco-friendly. Higher nimbolides (nearly 17 % higher) could be extracted using this technique. EXAMPLE 3: Laboratory tests were performed to demonstrate antibacterial activity of neem (Fraction A), Citrullus colocynthis (Fraction B), and combination of neem plus Citrullus colocynthis (Formulation with synergistic effect). Antibacterial activities of "Fraction A"; "Fraction B" and "Formulation" were evaluated separately. "Formulation" provided results of the synergistic effect of the two components. The invention reveals laboratory tests conducted on several pathogenic strains of bacteria as per details given below: Antibacterial activity of the said extracts against pathogenic bacterial strains e.g. E. coli (strain #1), Pseudomonas aeruginosa (strain # 2), Streptococcus mutans (strain # 3), Pseudomonas fluorescens (strain # 4), Klebsiella pneumoneae (strain # 5), Proteus mirabilis (strain # 6), Staphylococus aureus (strain # 7) was tested and given below. The activity is measured as inhibition zone (reported as diameter of the zone in mm). Example 3.1: Antibacterial activity of Fraction A (Neem) (Table Removed) IMTEC = Institute of Microbial Technology, (CSIR), Chandigarh, India Example 3.2: Antibacterial activity of Fraction B (Citrullus colocynthis) (Table Removed) Example 3.3: Antibacterial activity of the formulation comprising mixture of fractions A and B (Table Removed) EXAMPLE 4: A total of 60 volunteer subjects (for various treatments) with their age ranging between 18-30 years were selected from the Outpatient Department of Periodontics, Faculty of Dental Sciences, King George's Medical College, Lucknow. The criteria for the selection of subjects were as follows: (Table Removed) This study was divided into two phases: Phase I: The effectiveness of "Formulation" was clinically assessed against dental plaque. Dental plaque was also collected for "in vitro" study. Particulars of the individual, baseline plaque score and experimental plaque score were recorded on a Performa. Plaque accumulation was recorded using Turesky-Gilmore-Glickman modification (1970) of Quigley-Hein Plaque Index System as follows: (Table Removed) Plaque Collection: The plaque was collected from the facial and lingual/palatal surfaces of all teeth, except 3rd molars, using curettes; and was suspended in 5.0 ml of sterile phosphate buffered saline (PBS) solution in screw capped vial; and transported to laboratory for Colony Forming Units (CFU) analyses. Example 4.1: Efficacy of Fraction A (neem) on reduction of dental plaque at different segments (anterior, posterior, facial, lingual, upper and lower) using Quigley-Hein Scoring System (Table Removed) Example 4.2: Efficacy of fraction B (Citrullus colocynthis) on reduction of dental plaque at different segments (anterior, posterior, facial, lingual, upper and lower) using Quigley-Hein Scoring System (Table Removed) Example 4.3: Efficacy of the herbal formulation comprising mixture of Fractions A and B on reduction of dental plaque at different segments (anterior, posterior, facial, lingual, upper and lower) using Quigley-Hein Scoring System Also see Figs. (Table Removed) Example 5 Phase II: The effectiveness of the Azadirachta indica (Fraction A) extracts were tried against different grades of gingivitis. Thirty subjects with different grade of gingivitis in the lower anterior region were selected. These subjects were divided into three groups each comprising of 10 subjects according to the type of experimental extract used. Gingival health status was recorded by "Loe and Silness" (1963) gingival index. The gingival index used is reproduced below: (Table Removed) Gingivitis was recorded before starting the clinical trial. After that extract was applied on lower anterior inflamed gingival and the extract was given to the subjects for local application by the patient himself. Patients were advised to apply given extract once in the morning and second time in the evening with the help of cotton pellets for one week. During this period, patients were advised to continue their usual prophylactic procedures. After one week, gingivitis score were recorded on the proforma by the above method. Subjects were advised to apply the same extract for another one week. After second week, gingivitis was again recorded by the same method. The observations were recorded and statistically analyzed. Efficacy of Fractions A, B and the synergistic herbal formulation comprising mixture of A plus B on reduction in gingivitis (Table Removed) Example 6: Method of Bacterial Enumeration (Total Viable Count) The total number bacteria in baseline plaque and experimental plaque from subjects were enumerated by spread plate count method in following steps: a) Diluent Preparation: Phosphate buffered saline (PBS) (Himedia Laboratory Ltd. Mumbai) was dissolved water (9.55 gm/L) and the pH was adjusted 7.2. This solution was autoclaved at 15 lbs/inch (121 °C) for 15 minutes and was used as diluent. b) Preparation of Agar plates: The dehydrated plate count agar medium (Hi Media Laboratories Ltd. Mumbai) was used with following composition: (Table Removed) This agar medium was dissolved in distilled water (23.5 gm/L) and boiled in conical flask of sufficient capacity. The flask was cotton plugged and was placed in autoclave for sterilization at 15 lbs/inch2 (121° C) for 15 minutes. After sterilization, the molten agar in flask was immediately poured (20 ml/plate) into sterile Petri dishes on plane surface. The poured plates were left at room temperature to solidify and incubate at 37°C overnight to check the sterility of plates. The plates were dried at 50°C for 30 minutes before use. c) Preparation of Decimal Dilution: 4.5 ml of PBS was taken in test tube and cotton plugged. These tubes were sterilized by autoclaving. The decimal (ten-fold) dilution was prepared by initiating with 0.5 ml of plaque suspension, which was further processed with other PBS tubes in series for obtaining dilution of 1/10, 1/100, 1/1000 and so on. d) Inoculation (Plating): The properly marked agar plates were inoculated with 0.1 ml of plaque suspension and their decimal dilutions by using sterile glass pipettes. The inoculum on the agar surface was spread gently up to dryness with a sterile (by dipping in ethanol and flaming) and cooled "L" shaped glass spreader. e) Plate Counting: All the inoculated agar plates were incubated at 37°C for 24-48 hours. The number of colonies that appeared on each agar plate was counted and the results were expressed as colony forming unit (CFU)/ml after multiplying with dilution and inoculation factors for each plaque sample. All glassware used were manufactured by Borosil and sterilized in hot air oven at 170°C for 1 hour. f) Procedure: At the time of phase 1 clinical trial, oral prophylaxis was performed on all ten subjects and instructed not to clean their teeth by any method for three days. On fourth day, three day old plaque was disclosed by tetrazolium compound disclosing solution. This plaque was considered baseline plaque for each subject and was recorded on a specially designed proforma. After recording and collecting baseline plaque, three days gap was advised to all the subjects. During this period, subjects were advised to continue their routine oral hygiene measures. On seventh day, the plaque score was again reduced to zero in each subject. The test preparation was applied by operator himself with the help of cotton pellets twice daily on the facial and lingual/palatal surfaces of all teeth. After 5 minutes the subjects were asked to rinse with tap water. The procedure was repeated for three days in succession at the end of which plaque score was recorded and collected again. During the test period, subjects were abstained from performing any oral hygiene measure. All the formulations were tried in each subject by the same method as described above. Affectivity of Fractions A, B and mixture of A plus B on in vitro colony forming units (CFU) of bacteria causing dental plaque (Table Removed) EXAMPLE 7: In another study, the efficacy of the formulation (Mixture of Fractions A and B) was tested in vitro culture experiments. The formulation was compared against Chlorhexidine, Listerine and Betadine, the common mouth wash agents used by periodontal surgeons. Cell viability (toxicology to the cell) was measured. The results revealed that Chlorhexidine, Betadine were cytotoxic even at 0.001 %; Listerine was toxic at 10 and 100 %; it had potent cytotoxic effects. The formulation as proposed in this invention did not have any cytotoxicity at the concentration used in the invention. The test also revealed that the formulation had a reversible effect on cultured fibroblasts when the cell viability and protein quantification were analyzed. On the other hand Chlorhexidine, Listerine and Betadine damage the cells irreversibly. This supports the contention that the proposed formulation is non-toxic and is safe for use. Advantages The present invention provides several advantages over methods known in the prior art, in that: ♦ The present invention discloses a synergistic herbal formulation comprising an antioxidant from plant source preventing >61 % dental plaque and >25 % gingivitis applying on teeth and gums over a period of two weeks. ♦ The formulation is safe, non-toxic, biodegradable and without any side effect. ♦ The use of azadirachtin is avoided since this group of compounds has insect antifeedant and repellent properties and poor shelf life when dissolved in water. ♦ Active nimbolide rich fractions with pronounced antibacterial activity has been incorporated in the formulation; ♦ The present invention discloses extraction of fraction containing active glycosides from Citrullus colocynthis; ♦ The present invention allows the practitioner to isolate active fractions from neem and Citrullus colocynthis; ♦ There is a disclosure of invention and application of super critical fluid extracted fraction from neem for dental formulation; References 1. Saimbi C.S. and Charan Singh. ISP Bulletin 1984: 14. 2. Saimbi, C.S. Investigation of medicinal plants for dental disease. National Seminar on the use of traditional medicinal plants in skin care. CI MAP, Lucknow 1994, Nov. 25-24, p. 22. 3. Ooshima, T., Minami, T., Anano W, Tamura, Y. Hamada S. 1994. Caries Research 28 (3): 149. 4. Subh N., Saimbi C.S., Kapoor K.K., Dixit J and Nigam S.K. 1989. Effect of medicinal plants on the dental plaque. Thesis submitted for MDS periodontics, Lucknow University, 1989. 5. Lahanket, M.A., Rehman M.K. 1990. Deerghayu International 6 (21): 5-7. 6. Schmutterer H. 1990. Annu. Rev. Entomol. 35:271-297. 7. Schmutterer H 1995. In: The Neem Tree Azadirachta indica A. Juss. and Other Meliaceous Plants: Sources of Unique Natural Products for Integrated Pest Management, Medicine, Industry and Other Purposes, (ed) H Schumtterer, VCH Verlagsgesellschaft, Weinheim, Federal Republic of Germany, pp 696. 8. Schmutterer H 1995. In: The Neem Tree Azadirachta indica A. Juss. and Other Meliaceous Plants: Sources of Unique Natural Products for Integrated Pest Management, Medicine, Industry and Other Purposes, (ed) H Schumtterer, VCH Verlagsgesellschaft, Weinheim, Federal Republic of Germany, pp 696. 9. Siddiqui A. 1945. Current Sci. 11, 278. 10. Telia A 1977. Nig. Med. J. 7:258-263. 11. Rochanakij S. Thebtaranoult Y Yenjai C Yuthavong Y 1985. South East Asian J. Trop. Med. Public Health 16:66-72. 12. Okpanyi S.N., Ezeukwu G.C. 1981. Planta Medica 41:34-39. 13. Andrew, 1966. Encyclopedia of medicinal paints 1996: 1. 14. Gahuker, R.T. 1995. Neem in plant protection 1995. 1:8. 15. Wolinsky, L.E., Mania, S., Nachanani and Ling S. 1996. Dent Res. 75 (2). 16. Farooqi et al. US patent # 6,264,926. 17. Guhabakshi, D.N., Sarma, P.S. Pal, D.C. 1999. Alexicon of Medicinal Plants in India 1:221-228. 18. Saxena S. 1998. Neem in malaria control: Community perceptions and awareness in rural Kenya. In : Neem: Applications in Agriculture, Health Care and Environment, Proc International Conference Neem: Setting Goals for a Global Vision, Neem Foundation, Mumbai, India 1996, pp 59-61. 19. Saxena S. 1999. Development of neem for plant protection and medicinal uses in Africa. In Proc. International neem Conference, Vancouver, BC, Canada, 1999, Published by Neem Foundation, Mumbai, India 2002. 20. Chawla HS 1983 A new natural source of topical fluoride J. Ind. Dent. Assoc. 55:419-422. 21. Almas, K. 1999. Indian Journal of Dental Research 10(1): 23-26. 22. Masaki S. et al. (Terumo corporation ) 1985, Neem bark extracts, US Patent # 4,515,785 & Hot water extracts of neem, US Patent # 4,537,774. 23. Jarvis A.P. Morgan E.D. Edwards C. 1999. Phytochemical analysis 10:39- 43. 24. Kraus W 1995. Azadirachtin and other triterpenoids. In: The Neem Tree Azadirachta indica A Juss. and Other Meliaceous Plants: Sources of Unique Natural Products for Integrated Pest Management, Medicine, Industry and Other Purposes, (ed) H Schmutterer, VCH Verlagsgesellschaft, Weinheim, Federal Republic of Germany, pp 35-74. 25. Jarvis A.P., Johnson S., Morgan E.D., Simmonds M.J.S., Blaney W.M. 1997. J. Chemical Ecology 23:2841-2860. 26. Johnson S., Morgan E.D. 1997. J. Chromatog. 761:53-63. 27. Phillipson J.D. 1995. Phytochemistry 36:1319-1334. 28. Charles V., Charles J.X. 1992. Tropical Geogr. Med. 44:178-181. 29. Lewis W. H., Elvin-Lewis M. 1977. Medical Botany New York: John Wiley & Sons, New York, 515 pp. 30. Elvin-Lewis M. 1980. J. Prev. Dent. 6: 61-70. 31. Wolf P. et al. 1999, US Patent # 5,989,604; 2000, US Patent # 6,159,508 Xylitol-containing non-human foodstuff and method 32. Locke et al. 1994, Fungicide compositions derived from neem oil and neem wax fractions, US Patent # 5,298,251 and U.S. Ser. No. 07/456,762. 33. Wealth of India, 1994. vol. 3, p. 596-599 (1994). 34. Chopra R.N., Nayar S.L., Chopra I.C. 1956. Glossary of Indian Medicinal Plants, C.S.I.R. Publication, New Delhi, India, 1956. 35. Maatooq et al. 1997. Phytochemistry, 44: 187-190. 36. Gawarikar R., Mehta B.K. 1994. Ind. J. Chem. 33B: 897-898. 37. Bhandari et. al. 1974. Econ Bot. 28: 73. 38. Chaudhri etal. 1953. Pakist J. Sci. 5: 110. 39. Khan et al. 1956. Pakist J For. 6: 309. 40. Luthra et al. 1950. Indian Fmg. 11:10. 41. Saxena et al. 1983. Indian Fmg.33 (5): 37. 42. Okieimen et al. 1989. Biological Wastes Sub. 269: 7483. 43. M. Miro, Phytother. Res. 8, 159-168 (1995) 44. R. L. Metcalf, J. Chem. Ecol. 12, 1109-1124 (1986). 45. M. Miro et al., Phytother. Res. 9, 159-68 (1994) 46. J. M. Cassady and J. D. Dourous, eds., Academic Press, New York, 1980, pp. 247-254. 47. Guha J., Sen S.P. 1975. Plant Biochemical Journal 2: 12-28. 48. McMahon et al, U.S. Patent # 5,466,460 49. Branly et al. U.S. Patent # 5,484,587. 50. Metcalf et al. 1987. J. Econ. Entomol. 80: 870-875. 51. Lance D.R., Sutter G.R., 1991. J. Econ. Entomol. 84: 1861-1868. 52. Berdami; L. A. 2001, Composition and method for topical animal medication, US Patent # 6,274,555. 53. Subbiah, V. U.S. Patent # 5,925,356 54. Hatam et al. 1989. Phytochemistry 28(4): 1268-1271. 55. Socransky S.S. 1970. J. Dental Research 49: 223-228. 56. Lindhe J., Hamp S.E. Loe H. 1970. Journal of Periodontal Research 8: 1- 10. 57. Loe H., Theilade E., Jensen C.B., Schiott C.R. 1967. J. Periodont Res. 2: 282. 58. Harrison J.W.E., Sad'sbury G.B., Abotf, D.P., Packman, E.W. 1963. J. Periodontol 34: 334. 59. Fitzgerald R.J., Keyes P.H., Stoudt T.H., Spinell D.M. 1968. J Am. Dent Assoc 76: 301. 60. Gjermo P., Baastad K.L., Rolla G. 1970. J. Periodont Res. 5: 102. 61. Reddy J., Salkin L.M. 1976. J Period 47: 607. 62. Shiota T. 1953. J. Dent. Res. 35: 939. 63. Turesky S, Gilmoer N.D., Glickman I. C. 1967. J. Periodontol 38: 142. 64. Walter H. Lewis, Medical Botany-Plants Affecting Man's Health, 246-47, John Wiley & Sons 1977. 65. Maurice M. Iwu, Handbook of African Medicinal Plants, 124-28 (CRC Press 1993). 66. U.S Pat. Nos. 5,371,254; 5,472,684 and HI 541 67. Howard H. S. 1998. Chewing gum containing a teeth whitening agent, US Patent #5,824,291. 68. Ahmad, et al. 1991, Dentifrice, US Patent # 5,009,886. 69. Scheller; Hans-Ulrich, 1980, Paste and powder dentifrices US Patent # 4,223,003. 70. Miller S. E. and Simone A. J. 1999. Chewing stick made from natural fibers, US Patent # 5,939,049. 71. Nabi; N. et al., 1995, Oral compositions for plaque and gingivitis, US Patent # 5,472,684. 72. Seabrook, Jr. et al. 1999, Polymers containing antimicrobial agents and methods for making and using same, US Patent # 5,906,825. We Claim: 1. A process for the preparation of a dental care herbal formulation comprising 2 to 5.5% w/v (Azadirachta indica from bark and leaves); 0.5 to 2.5% w/v (Citrullus colocynthis); 0.1 to 0.4% w/v (Cucumis sativus): 82 to 97% w/v of carrier or additive, wherein the said process comprising the steps of: a. extracting said bark and leaves using a commercial blender at a temperature of 10 to 25.degree. C, preferably at 20.degree. C. and in an aqueous solution of polar solvents; b. excluding tannins from the extract of step a by liquid phase extraction using a non-polar organic solvent and a polar solvent; b. concentrating and partitioning the above extract obtained from step (b) by liquid phase extraction using a polar and a non-polar solvent and obtaining a polar fraction comprising rich in nimbolides as component A; c. extracting plant parts of Citrullus colocynthis, preferably underground parts, using a homogenizer at 7000 to 8000 revolution per minute in an aqueous polar solvent; d. purifying the active constituents from above extract in step (d) by concentrating and partitioning through liquid phase extraction using a polar and a non-polar solvent to obtain polar phase as component B; e. extracting an anti-oxidant fraction from Cucumis sativus by cold extraction using aqueous polar solvents at temperature ranging from 10 to 25.degree. C. using a tissue homogenizer, to obtain the polar fraction as component C; f. mixing component A from Azadirachta indica, component B from C. colocynthis, component C from C. sativus, a carrier in a ratio ranging from 2 to 5.5% w/v, 0.5 to 2.5% w/v, 0.1 to 0.4% w/v, and 82 to 97% w/v respectively to obtaining a herbal synergistic dental care formulation. 2. The process as claimed in claim 1, wherein the polar solvent used is selected from the group consisting of methanol, ethanol, acetone, and water. 3. The process as claimed in claim 1 wherein the non-polar solvents used are selected from the group consisting of hexane, chlorohexane, petroleum ether, chloroform, and ethyl acetate. 4. The process as claimed in claim 1 wherein component A can be alternatively extracted by super critical fluid extraction using CO.sub.2 as carrier gas, followed by partitioning of the said fraction by liquid phase extraction using a polar and a non polar solvent, to obtain a polar fraction rich in nimbolides as component A. 5. The process as claimed in claim 1 wherein the method comprises the application of the formulation to said human's teeth and gums. 6. A dental care herbal formulation prepared by the process as claimed in claim 1-5, useful for inhibiting periodontal disease in a human in need thereof. 7. The dental care herbal formulation of claim 6, wherein, the ratio of bark and leaves of Azadirachta indica ranges from 1 to 2.5% and 2 to 10%, respectively. 8. The dental care herbal formulation of claim 6, wherein the Citrullus colocynthis is from a plant part selected from the group consisting of the fruit of Citrullus colocynthis and the roots of Citrullus colocynthis. 9. The dental care herbal formulation of claim 6, wherein the antioxidant is obtained from the fruit peels of Cucumis sativus and is present in said formulation in a range of from 0.1 to 0.4%w/v. 10. A dental care herbal formulation useful for treating dental plaque and dental gingivitis in human in need thereof. 11. The dental care herbal formulation of claim 6, wherein the carrier used is 5 to 18% w/v edible grade ethanol in an aqueous solution. 12. The dental care herbal formulation of claim 6, wherein said formulation is in the form of a lotion, cream, mouthwash, tooth or gum paste.

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