FIELD OF THE INVENTION

The present invention particularly relates to skin lightening agent comprising cis-stilbene derivative as melanin synthesis inhibition and/or dendrite elongation inhibition active and cosmetic and dermopharmaceutical compositions comprising the same. More particularly, the present invention is directed to said skin lightening compositions comprising said cis-stilbene derivative as melanin synthesis and dendrite elongation inhibiting active for whitening of the skin in association with a cosmetically acceptable vehicle with or without other skin benefiting agents.

More specifically, the present invention provides a simple and cost effective skin lightening agents comprising cis-stilbene derivative preferably selected from 3,4,3',5'-tetramethoxy-cis-stilbene of Formula 1 as an active ingredient in effective amounts which can be used singly or in combination with cosmetically/ dermopharmaceutically acceptable vehicle/ carriers in related skin lightening compositions.

3,4,3',5'-Tetramethoxystilbene (Formula 1)

BACKGROUND AND PRIOR ART

Skin lightening is an important contributor to skin care attribute of cosmetic preparation /compositions, especially among darker skinned people including Asian population. Such a need includes a lightening of basal skin tone. Also it is desired by persons having spots, freckles or lesions which are hyperpigmented and thus need to be diminished. In other situations subjects may desire to reduce their natural skin colour or the skin darkening caused by exposure to intense sun rays.

Ultra violet rays and other forms of irradiation cause tanning. The colour change (tanning) of the skin tissue has its origin in melanin synthesis and the stagnation of the melanin inside the pigmented cells under the influence of hormones and stimulation by ultraviolet exposure. Freckles, wrinkles and the like are formed by the stagnation and the fixation of melanin inside the surface layer of the skin at some places.

As regards melanin synthesis on the skin surface, tyrosinase, which is an oxidative enzyme synthesized in the pigmented cells, oxidizes and polymerizes tyrosine thus synthesizing melanin.

There is extensive research into ways of inhibiting melanin synthesis or reducing dendrite length and its fixation process in order to create a cosmetic whitening agent.

Rumex extract acts on melanogenesis by competitive inhibition of tyrosinase. The available data suggests that Rumex extract is able to bind onto the enzyme's active site, thereby inhibiting the substrate reduction which normally leads to melanin production (Simonot et.al., Cosmetics & toiletries magazine, 2002, 117, 51-56).

WO 2010115472 (A2) teaches on the combination of an extract of at least one Rumex plant species and S-hexadecene-l,16-dicarboxylic acid to show synergistic effect on the inhibition of melanin synthesis.

The Japanese patent, 2003-073224 teaches that the melanin formation inhibitor was obtained by including a solvent extract from one or more species of plants selected from Croton eluteria, Elettaria caradamomum and Carum carvi as an active ingredient.

Philippe has mentioned in US patent 6,306,376, 2001 that arbutin monoesters can be used in cosmetic or dermatological composition as a tyrosinase inhibitor and /or as melanin synthesis inhibitor.

The extracts with hot water, or extracts with ethanol, hexane, etc. of stems, branches, leaves, etc. of Cistus ladaniferus L, Cistus creticus L, Cistus monoperiensis L, Cistus salvifolius, etc. showed a strong inhibitory activity on production of melanin, a cell-activating activity and an anti-bacterial activity and labdanolic acid derivatives: labd-7-en-15-oic acid, labd-8(17)-en-15-oic acid, and labd-8-en-15-oic acid were responsible for strong inhibitory activity on production of melanin, a cell-activating activity and an anti-bacterial activity (Tamai et al., USP. 6,313,214; 2001)

Another US Patent (Matsuda et al., USP 6,759,557, 2004) discloses a macrocyclic ketone or hydroxy or hydroxyketone to inhibit the production of melanin, thereby controlling the skin pigmentation turning the skin fairer.

There are several agents: vitamin C, cysteine, kojic acid, arbutin, glutathione, hydroquinone and other efficient compounds extracted from natural substances are known for inhibiting melanin synthesis by lowering the tyrosinase activity or by bleaching and lightening the colour of the synthesized melanin. However, the stability, safety and whitening effect of these compounds are not sufficient, and no satisfactory whitening agent has been achieved till date.

The dendricity of melanocytes is regulated by various intrinsic and extrinsic factors. Addition of agents that increase the intracellular levels of cyclic adenosine monophosphate, dibutyryl cyclinc adenosine monophosphate or isobutylmethyl xanthine (IBMX), all of which has strong effects on dendrite formation (Glynis et. al., J. Invest. Dermatol., 2007, 127, 668-675). Each melanocyte makes contact with around 30-40 keratinocytes and this constitutes the epidermal melanin unit. Mammalian melanocytes in the epidermal unit extend their dendrites towards keratinocytes in response to UV rays in addition to proliferation and melanin synthesis leading to tanned skin (Suzuki et al., In Vitro Cell Dev. Biol. Anim., 1993, 29, 419-426). Also, increased number of dendrites and increase in the length of dendrites, higher levels of transfer of melanin to keratinocytes is an established phenomenon while subjected to the UV rays. Thus skin colour can be determined/ regulated by modulating the elongation of dendrites or dendrite numbers (Akihiro, Fragr J, 2005, 33, 30 and Tada et. al., Bio. Ind., 2005, 22, 12-17).
Under normal conditions it is not the number of melanocytes in the skin that determines the degree of pigmentation but their levels of activity and the transfer of melanin in to the neighboring keratinocytes is the important factor.

Phospholipse A2 secreted by kertinocytes is also known to mediate melanocyte dendricity. The effective transfer of the synthesized melanin by the melanocytes to the keratinocytes plays a very critical role in the skin colour than the extent of synthesis of melanin by the melanocytes. The most effective mode of transfer of the melanin to the keratinocytes is governed by the dendritic phenomena of the melanocytes. Abrogating the dendriticity of melanocytes is of great importance for controlling skin colour (Yuko et. al., Biochimica et Biophysica Acta, 2006, 1769, 487).

There are several dendrite inhibitors already reported in the literature. Benzoquinone group of chemicals that includes methyl ophiopogonanone B and centaureidin, benzopyranone, xanthanone derivatives were reported to inhibit dendrite formation in melanocytes and effectively affect the skin colour (Yuko et. al., Biochimica et Biophysica Acta, 2006, 1769, 487). Inhibiting the dendrite formation in melanocytes is thought to be more effective in the related prior arts than tyrosinase inhibition for the purpose of skin lightening/ whitening cosmetics (Tada et. al., USP: 7, 141, 601, 2006).

US patent 7141601 and Korean patent 20050084088 A by Tada et al. are directed to a method of inhibiting the elongation of melanocytic dendrites through a skin preparation comprising of methylophiopogonanone B (2, 3-dihydro-3[(4-methoxyphenyl) methyl]-5, 7-dihydroxy-6, 8-dimethyl-4H-l-benzopyran-4-one) extracted from the tubers of Ophiopogon japonicus ker-Gawler.

JP 2004143073 A further illustrates a 1, 3-dioxolane derivative of methyl-ophiopogonanone B to possess the same property of inhibiting the elongation of melanocytic dendrites.

JP 2001335420 A is related to a skin lotion comprising the essence of rhizomes of Acorus calamus; JP 2001335421 A is directed to the essence of Sophora subprostata; JP 2003081748 A teaches a fruit essence of Forsythia suspensa Thunb. Vahl of Oleaceae; JP 2003081747 A illustrates a skin care preparation comprising the essence of Lonicera japonica Thunb preferably the essence of bulbs, leaves and stems; JP 2002053421 A is directed to a cosmetic skin care preparation comprising Maackiain derived form the rhizomes of Sophora subprostrata; JP

A comprises of a skin care preparation comprising the essence of the fruit of Phaseolus radiatus L; JP 2003081807 A is related to a bleaching cosmetic comprising an essence of Calendula officinalis L and preferably an essence of a flower bud, a leaf and a stem; JP 2003113027 (A) is directed to a bleaching cosmetics by incorporating the essence of preferably enlarged root of plant of genus Ophiopogon such as Ophiopogon japonicus ker-Gawler etc.; JP 2003252742 A discloses a skin preparation having high bleaching effect comprising yeast extract as the active ingredient; JP 2001335502 A is related to a skin care preparation comprising the essence of rhizomes of Nardostachys jatamansi; JP 2002020303 A illustrates a cosmetic skin care preparation comprising the essence of rhizome of Thalictrum minus var. hypoleucum; JP 2004250354 A is related to a cosmetic preparation comprising extract of a plant belonging to Achillea family; JP 2003081746 A is directed to a bleaching cosmetics comprising an essence of Uncaria gambhir ROXBURGH, preferably the essence of leaves and sprigs; JP

A is directed to a cosmetic skin care preparation including the essence of a ripe dried seed, preferably a fruit of Prunus armeniaca L. var. ansu axim. of the family Rosaceae; JP 2001335485 A directed to a skin care preparation comprising of a berberine derivative; all of which have the dendrite inhibition property.

However, some of these products are associated with simultaneous disadvantages associated with each of them. For example, Acorus calamus is considered to be cytotoxic as reported by Padmaja et al. in Fitoterapia. 2002, 73, 508-510.

EP 1570838 Al is mainly directed to dendrite elongation inhibitor for melanocytes comprising of centaureidin that was used directly or in the form of a physiologically acceptable salt in cosmetic skin preparations intended for alleviating dyschromatosis to which the amount of melanin produced less contributes resulting form the accelerated migration of melanin granules from melanocytic dendrites.

Further in our co-pending patent application no. 3045/CHE/2011 dt. 05.09.2011 there is disclosed dendrite elongation inhibitory effect of some trans stilbene derivatives and specifically illustrates the dendrite elongation inhibitory effect of trans tetramethoxy piceatannol that was either obtained synthetically and/or from plant extracts of Crotalaria medicaginea Lam.

While inhibiting the elongation of dendrites that occurs when melanocytes allow melanin granules to migrate is a well known skin lightening mechanism not so many lightening agents utilizing such a mechanism are known in the art and it can thus be said that there is a strong need in the art for the development of new skin lightening agents favouring both the mechanistic pathways of inhibiting the elongation of dendrites and/or inhibiting melanin synthesis thus favour enhanced skin lightening characteristics.

Several prior arts on plant materials are available in alternative systems of medicine like Ayurveda and ethno medicine or folklore recommending herbal remedies for inhibitory activity on production of melanin and dendrite elongation inhibition or skin whitening agents.

Therefore, it would be clearly apparent from the above said state of the art that on one hand there is a need for new, effective and safe melanin synthesis inhibitory agent that would also be effective towards inhibition of dendrite elongation so as to favour enhanced skin whitening, and on the other, there also remains a need to explore processes to obtain said selective actives.

OBJECTS OF THE INVENTION

It is thus the primary object of the present invention to provide for skin lightening agent that would on one hand inhibit the synthesis of melanin and on the other would also be equally effective in inhibiting dendrite elongation to behave as an effective skin lightening agent with enhanced skin lightening characteristics.

Another object of the present invention is to provide for a skin lightening composition comprising said skin lightening agent in effective amounts in combination with cosmetically/ dermopharmaceutically acceptable vehicle/ carriers with or without other skin benefiting agents which would be efficacious, safe and compatible to the skin with better consumer acceptance.

Yet another object of the present invention is to provide for said melanin synthesis inhibiting agent and dendrite elongation inhibitory agent or skin lightening agent compatible for incorporation in variety of skin care formulations and the like with anti-tanning property also involving said melanin synthesis inhibition and/or dendrite elongation inhibitory active that can be sourced simply and cost-effectively via., synthesis or from any natural renewable resource materials such as plants.

Yet another object of the present invention is to provide for an improved cosmetic skin lightening composition which would have other beneficial attributes of being user friendly in terms of ease of application, improved shelf life, and requiring reduced frequency of application.

Still another object of the present invention is directed to the formulation of the skin lightening composition using effective amounts of said active ingredients obtained via synthesis or from plant extracts with good skin compatibility.

SUMMARY OF THE INVENTION

Thus according to the basic aspect of the present invention there is provided a skin lightening agent comprising cis-stilbene derivative as melanin synthesis inhibition and/or dendrite elongation inhibitory active.

According to another preferred aspect of the present invention there is provided the said skin lightening agent wherein said melanin synthesis inhibition and/or dendrite elongation inhibitory active comprising cis-stilbene derivatives comprises 3,4,3',5'-tetramethoxy-cis-stilbene of Formula 1 as represented hereunder 3,4,3',5'-
Tetramethoxystilbene (Formula 1)

Importantly, it is the selective finding of the present invention that 3,4,3',5'-teramethoxy-cis-stilbene of Formula 1 significantly and surprisingly reduces the production of melanin and also inhibits dendrite elongation responsible for skin pigmentation - in melanocytes which are the cells that synthesize melanin vis-a-vis the trans isomer thus providing for superior skin lightening agent with enhanced skin lightening characteristics. Particularly noteworthy is that the skin lightening agent of the present invention is found to be unexpectedly more potent than standard reference molecules such as Arbutin.

The present invention thus provides for surprisingly efficacious skin lightening agent comprising cis-stilbenes and specifically selective 3,4,3',5'-teramethoxy-cis-stilbene of Formula 1 and skin lightening compositions comprising the same.

According to yet another preferred aspect of the present invention there is provided the said skin lightening agent wherein said melanin synthesis and dendrite elongation inhibitory actives comprising cis-stilbene derivatives preferably comprises S^^'^'-teramethoxy-cis-stilbene of Formula 1 which is either synthesized or sourced from natural renewable plant sources.

According to another preferred aspect of the present invention there is provided said active of Formula 1 that inhibits the synthesis of melanin by about 72 % and inhibits the elongation of dendrites by about 100% at the levels of about 5ug/ml.

According to another aspect of the present invention there is provided a skin lightening composition for topical use comprising melanin synthesis and dendrite elongation inhibitory active comprising cis-stilbene derivatives And a cosmetically acceptable vehicle with or without other skin benefiting agents

According to yet another preferred aspect of the present invention there is provided a skin lightening composition for topical use wherein the said melanin synthesis and dendrite elongation inhibitory active comprising cis-stilbene derivatives preferably comprises 3,4,3',5'-teramethoxy-cis-stilbene of Formula 1

3,4,3'>5'-Tetramethoxystilbene (Formula 1)

According to yet another preferred aspect of the present invention there is provided said skin lightening composition for topical use wherein said melanin synthesis inhibition and/or dendrite elongation inhibitory active is comprised in an amount of
a. 0.0001 wt% to 20 wt. %, preferably 0.001 wt% to 10 wt% and more preferably and 0.01 wt% to 5 wt%

According to yet another preferred aspect of the present invention there is provided said skin lightening composition for topical use comprising a leave-on or a wash-off product adapted for topical delivery in the forms selected from of creams, ointments, emulsions, gels, lotions, oils, sticks, sprays, soaps, packs, wraps, woven or nonwoven wipes, films or patches as a vehicle for topical application of the said skin lightening composition.

According to still another preferred aspect of the present invention there is provided the said skin lightening composition for topical use wherein said melanin synthesis and dendrite elongation inhibitory active comprises selectively pure cis-stilbene compounds or preferably 3,4,3',5'-teramethoxy-cis-stilbene of Formula 1, either as a pure compound or as at least one ingredient in the semi pure extract of the reaction mixture or plant extract.

The ingredients essentially employed in such a composition are surfactants, emulsifiers emollients, silicones, thickeners, antioxidants, sunscreen agents, chelating agents, perfumes, opacifiers, colors, antimicrobial agents, herbal extract/ compounds, pH adjusting agents and water to qs.

The composition may contain usually employed vehicle such as may be aqueous, anhydrous or an emulsion. Preferably, the compositions are aqueous or an emulsion, especially water-in-oil or oil-in-water emulsion, preferentially oil in water emulsion. Water when present will be in amounts which may range from 5 to 99%, preferably from 20 to 85%, optimally between 40 and 80% by weight.

According to a still further aspect of the invention the cosmetic composition may contain other various other skin benefit agents, plasticizers, elastomers, calamine, pigments, antioxidants, chelating agents, and perfumes, as well as organic/inorganic sunscreens and including such sunscreens as UV diffusing/protection agents, typical of which is finely divided Titanium oxide and Zinc oxide.

A still further aspect of the invention the cosmetic composition of the present invention may optionally contain other adjunct minor components / ingredients such as including coloring agents, opacifiers, antimicrobial agents, pH adjusting agents and perfumes. Amounts of these other adjunct minor components may range anywhere from 0.0001% up to 20% by weight of the composition.

The composition may also contain suitable skin benefit agents include anti-aging, wrinkle-reducing, skin whitening, anti-acne, and sebum controlling/ reducing agents. Examples of these include alpha-hydroxy acids and esters, beta-hydroxy acids and esters, polyhydroxy acids and esters, kojic acid and esters, ferulic acid and ferulate derivatives, vanillic acid and esters, dioic acids (such as sebacic and azeleic acids) and esters, retinol, retinal, retinyl esters, hydroquinone, t-butyl hydroquinone, mulberry extract, licorice extract, and glycosides of benzyl protocatechuate derivatives.

Suitable cosmetic carriers are well known to one skilled in the art. The cosmetic bases may be any bases which are ordinarily used for skin benefit agents and are not thus critical. Specific preparations of the cosmetics to which the skin benefit agents of the invention is applicable include creams, ointments, emulsions, lotions, washes, masks, packs, oils, sprays / aerosols and wipes. Cream bases are, for example, beeswax, cetyl alcohol, stearic acid, glycerine, propylene glycol, propylene glycol monostearate, polyoxyethylene cetyl ether and the like. Lotion bases include, for example, oleyl alcohol, ethanol, propylene glycol, glycerine, lauryl ether, sorbitan monolaurate and the like.

The cosmetically acceptable vehicle may act as a diluant, dispersant or carrier for the skin benefit ingredients in the composition, so as to facilitate their distribution when the composition is applied to the skin.

Besides water, relatively volatile solvents may also serve as carriers within compositions of the present invention. Most preferred are monohydric C1-C3 alkanols. These include ethyl alcohol, methyl alcohol and isopropyl alcohol. The amount of monohydric alkanol may range from 1 to 70%, preferably from 10 to 50%, optimally between 15 to 40% by weight.

Emollient materials may also serve as cosmetically acceptable carriers. These may be in the form of silicone oils and synthetic esters. Amounts of the emollients may range anywhere from 0.1 to 50%, preferably between 0.5 and 30% by weight.

Silicone oils may be divided into the volatile and non-volatile variety. The term "volatile" as used herein refers to those materials which have a measurable vapor pressure at ambient temperature. Volatile silicone oils are preferably chosen from cyclic or linear polydimethylsiloxanes containing from 3 to 9, preferably from 4 to 5, silicon atoms. Nonvolatile silicone oils useful as an emollient material include polyalkyl siloxanes, polyalkylaryl siloxanes and polyether siloxane copolymers. The essentially non-volatile polyalkyl siloxanes useful herein include, for example, polydimethyl siloxanes with viscosities of from about 1 to about 25 million centistokes at 25°C. Among the preferred non-volatile emollients useful in the present compositions are the polydimethyl siloxanes having viscosities from about 10 to about 2,00,000 centistokes at 25.degree. C.

Among the ester emollients are: (1) Alkenyl or alkyl esters of fatty acids having 10 to 20 carbon atoms. (2) Ether-esters such as fatty acid esters of ethoxylated fatty alcohols. (3) Polyhydric alcohol esters. (4) Wax esters (5) Sterol esters.

Fatty acids having from 10 to 30 carbon atoms may also be included as cosmetically acceptable carriers for compositions of this invention.

Humectants of the polyhydric alcohol-type may also be employed as cosmetically acceptable carriers in compositions of this invention. The amount of humectant may range anywhere from 0.5 to 30%, preferably between 1 and 15% by weight of the composition.

Thickeners/ rheology modifiers may also be utilized as part of the cosmetically acceptable carrier of compositions according to the present invention. Amounts of the thickener may range from 0.0001 to 10%, usually from 0.001 to 5%, by weight.

Collectively the water, solvents, silicones, esters, fatty acids, humectants and/or thickeners will constitute the cosmetically acceptable carrier in amounts from 1 to 99.9%, preferably from 80 to 99% by weight.

An oil or oily material may be present, together with an emulsifier to provide either a water-in-oil emulsion or an oil-in-water emulsion, depending largely on the average hydrophilic-lipophilic balance (HLB) of the emulsifier employed.

Surfactants may also be present in cosmetic compositions of the present invention. For leave-on products, total concentration of the surfactant will range from 0.1 to 40%, preferably from 1 to 20%, optimally from 1 to 15% by weight of the composition. For wash-off products, such as cleansers and soap, total concentration of surfactant will range at about 1 to about 90%. The surfactant may be selected from the group consisting of anionic, nonionic, cationic and amphoteric actives. The inventive cosmetic compositions optionally contain a lathering surfactant. By a "lathering surfactant" is meant a surfactant which, when combined with water and mechanically agitated, generates a foam or lather.

Preferably, the lathering surfactant should be mild, meaning that it must provide sufficient cleansing or detergent benefits but not overly dry the skin, and yet meet the lathering criteria described above. The cosmetic compositions of the present invention may contain a lathering surfactant in a concentration of about 0.01% to about 50%.

In the cosmetic compositions of the invention, there may be added various other plasticizers, elastomers, calamine, pigments, antioxidants, chelating agents, and perfumes, as well as organic sunscreens and sunscreens such UV diffusing agents, typical of which is finely divided titanium oxide and zinc oxide.

Other adjunct minor components may also be incorporated into the cosmetic compositions. These ingredients may include coloring agents, opacifiers, and perfumes.
Amounts of these other adjunct minor components may range anywhere from 0.001% up to 20% by weight of the composition.

The cosmetic skin composition of the present invention additionally may include anorganic UV-radiation protection agents to provide protection from the harmful effects of excessive exposure to sunlight. Organic UV-radiation protection agents for purposes of the inventive compositions are organic UV-radiation protection agents having at least one chromophoric group absorbing within the ultraviolet range of from 280 to 400 nm.

Preferred organic sunscreens are either single UV-radiation protection agents or combinations of different UV-radiation protection agents so as to absorb the entire UV range.

The amount of the organic UV-radiation protection agents in the personal care composition is generally in the range of about 0.01% to about 20%, preferably in the range of about 0.1% to about 10%.

Preferably the said organic UV-radiation protection agent is present in an amount of about 1 wt % to about 10 wt % of said cosmetic composition;

The inorganic or physical sunscreens are in the range of 1-30% by weight of the composition.

Organic antioxidant in the composition of the invention suitable for use include amino acids and its derivatives, imidazoles and derivatives thereof, peptides, and derivatives thereof, carotenoids, carotenes or derivatives thereof, chlorogenic acid and derivatives thereof, lipoic acid and derivatives thereof, aurothioglucose, propylthiouracil and other thiols and salts thereof, dilauryl thiodipropionate, distearyl thiodipropionate, thiodipropionic acid and derivatives thereof and sulfoximine compounds and also (metal) chelating agents, alpha-hydroxy acids, humic acid, bile acid, bile extracts, bilirubin, biliverdin, boldin, EDTA, EGTA and derivatives thereof, unsaturated fatty acids and derivatives thereof, folic acid and derivatives thereof, ubiquinone and ubiquinol and derivatives thereof, vitamin C and derivatives, tocopherols and derivatives, vitamin A and derivatives, and coniferyl benzoate of gum benzoin, rutic acid and derivatives thereof, alpha-glycosylrutin, ferulic acid, furfurylidene glucitol, camosine, butylhydroxytoluene, butylhydroxyanisole, nordihydroguaiacic acid, nordihydroguaiaretic acid, trihydroxybutyrophenone, uric acid and derivatives thereof, mannose and derivatives thereof, superoxide dismutase, and inorganic antioxidants like, Zinc and derivatives thereof, Selenium and derivatives thereof,

Further the UV light protection factors or antioxidants can be added in amounts of from 0.01 to 25% by weight, preferably 0.03 to 10% by weight and in particular 0.1 to 5% by weight, based on the total amount in the preparations.

To improve the flow behavior, hydrotropes can be added, such as, for example, ethanol, isopropyl alcohol, or polyols, can also be used. Such additives can be incorporated in amounts of 0.1 to 15% by wt.

The composition according to the present invention involves skin lightening agent or the above melanin synthesis inhibiting agent intended primarily as a product for topical application to skin for the purpose of skin lightening. In use, a small quantity of the composition, for example about 0.1 to about 5 ml can be applied to exposed areas of the skin, from a suitable container or applicator and, if necessary, it is then spread over and/or rubbed into the skin using the hand or fingers or a suitable device for desired skin benefit activity.

The details of the invention, its objects and advantages are explained hereunder in greater detail in relation to non-limiting exemplary illustrations as per the following examples:

EXAMPLES:

Example 1- Preparation of B.^S'.S'-teramethoxy-cis-stilbene of Formula 1

Stage-1:

Mixture of 3,5-dimethoxybenzaldehyde (5g) and 2-(3,4-dimethoxyphenyl) acetic acid (6g) were taken in 2.8ml of acetic anhydride and refluxed gently at 80-90°C in the presence 4.2 ml of anhydrous triethylamine for 2 hrs. The progress of the reaction was monitored by TLC. After completion of the reaction as checked by TLC, the reaction mixture was quenched in crushed ice and the solid thrown out was filtered from water, the product was washed with excess of water and dried. The dried product weighs 8.0g (Yield = 77%) and it was identified as 2-(3, 4-dimethoxyphenyl)-3-(3, 5-dimethoxyphenyl)acrylic acid (DMPDMPAA).

Stage-2:

5g of DMPDMPAA [2-(3,4-dimethoxyphenyl)-3-(3,5-dimethoxyphenyl)acrylic acid] was taken in 18.7 ml of quinoline (10 ml) in 100 RB flask, to which 0.5 g of copper chromate (10% w/w) was added and refluxed on a heating mantle at 210-220°C for 2 hrs. After cooling the reaction mixture, 10% hydrochloric acid was added to convert the quinoline to salt form. The aq. solution was extracted with ether (2X100ml), combined the ether solution, washed with 10% sodium bicarbonate solution, dried over anhydrous sodium sulphate and concentrated under reduced pressure to get mixture of cis and trans-stilbene derivatives (1.9g, 44%).

Stage-3: Purification and characterization

The mixture from stage 2 was purified by silica gel column chromatography using hexane: chloroform to get 350 mg of 3, 4, 3', 5'-tetramethoxy-cis-stilbene of Formula 1.
The stilbene derivative of the present invention, 3, 4, 3', 5'-teramethoxy-cis-stilbene of Formula 1, displayed the following characteristics. On thin layer chromatography using a pre-coated silica gel plate (Merck 1.05554.0001), the isolated substance provides a spot with an Rf value of 0.53 in hexane: ethyl acetate 8:2. The UV(CHCI3) spectrum shows an absorbance value at 216, 283, 292, 327 nm, IR spectrum values are at 3392 (br), 1722, 1640, 1595, 1485, 1114,1070 and 833 cm"1 and other characteristic signals, Proton NMR values in CDCI3 (400 MHz) are: 5 3.6 (3H, s), 3.61 (6H, s), 3.8 (3H, s), 6.3 (1H, s), 6.4 (2H, s), 6.42 (2H, d, J=7.2 Hz), 6.68 (1H, d, J=8.0 Hz), 6.76 (1H, s), 6.77(1H, d, 3=8.0 Hz); Carbon NMR values in CDCI3, 100 MHz): 5 55.3, 55.3, 55.6, 55.8, 99.6, 106.7, 106.7, 110.7, 111.8, 122.1, 128.8, 129.7, 130.3, 139.6, 148.3, 160.6.

Example 2- Biological assays- Melanin inhibition

This example demonstrates the method of determining the melanin inhibition activity of the specially preferred compound/ formulations of the invention by cell culture method by estimating the melanin content in B16F10 cells.

a) Assay for melanin content in melanocytes Reagent preparation:

1. IN NaOH

2. NaOH/DMSO - Solution containing 0.2 N NaOH and 20% DMSO. To 6 ml of water add 2 ml of DMSO and mix to dissolve. Add 2 ml of 1 N NaOH and mix.

3. Ethanohether (1:1) - To 1 ml ethanol add 1 ml ether and mix.

4. 2% Triton-X-100 - 2 ml of triton-X-100 in 98 ml of water.

Protocol:

1. Remove medium from melanocytes.

2. Wash the cells twice with PBS. Keep the dish slanted for one minute to collect all
the PBS and remove the remaining PBS.

3. Add 0.5 ml of 2% triton-x-100 and scrape the cells. Transfer the lysate to an eppendorf tube. Incubate for 1 hour on ice.

4. Centrifuge for 10 minutes at 10,000 rpm at 4°C.

5. Transfer the supernatant to a fresh tube. Use the supernatant for protein estimation.

6. Pellet contains melanin. Wash the pellet with 0.5 ml of ethanol:ether. Add 0.5 ml of ethanol:ether to the pellet. With a 1 ml tip, pipette the pellet up and down several times to break the pellet.

7. Centrifuge for 10 minutes at 10,000 rpm at 4°C.

8. Remove the supernatant.

9. Lyse the pellet in 0.5 ml NaOH/DMSO solution.

10. Measure absorbance at 400 nm.

11. Used Sigma synthetic melanin to prepare a standard curve.

12. Melanin inhibition was expressed in percentage.

Table: 1 - Comparison of the melanin inhibition

It is thus surprisingly found by way of the present invention that the cis-stilbene derivatives preferably 3,4,3',5'-teramethoxy-cis-stilbene of Formula 1 is unexpectedly efficacious over the trans isomer in inhibiting the synthesis of melanin wherein the % inhibition is 9 times more when compared to the trans isomer.

Example 3: Biological assay- Dendrite elongation inhibition

This example demonstrates the method of determining the dendrite elongation inhibition activity of the specially preferred extract/ compound/ formulations of the invention through cell culture method by estimating the length of dendrites.

The melanocyte cells, B16F10 were used for the present study. The cells were cultured in DMEM in the presence of 5% carbon dioxide, 10% serum, Pencillin (lOOug/ml), streptomycin (50ug/ml), Amphotericin B. (2.5ug/ml). l X 105 cells were seeded in 60 mm cell culture dish and were incubated with and without the test material for 24 hrs.

After 24 hr incubation, the cells were examined under an inverted microscope and the dendrite length was measured (USP 7141601B, 2006). The percentage of inhibition was calculated and recorded in Table 2.

Table: 2 - Comparison of the % inhibition of the dendrite length

It was also surprising that the % inhibition of the dendrite length by cis-stilbene derivatives preferably 3,4,3',5'-teramethoxy-cis-stilbene of Formula 1 of the present invention is unexpected when its efficacy vis-a-vis the trans isomer documented under the co-pending patent application no. 3045/CHE/2011 dt. 05.09.2011 is considered.

Example: 4- Preparation of Skincare cream

Table 3.



1. Heat Phase A to 75 degrees C on water bath and melt the mixture under stirring.

2. After sterilsation of water, transfer the water in to the main mixture and disperse the glycerin.

3. Disperse Phase C material, add Phase C to Phase B under high speed stirring. Then add Phase A to Phase XBC and stir for 5 minutes.

4. Transfer the phase D, into Phase ABC at high speed and stir for 5 minutes.

5. Dissolve EDDA- DS from Phase E, add to Phase ABCD and stir for 3 minutes.

6. Add Phase F ingredients at 75 degree C and stir for 2 minutes. Cool the material
to 45 degree C by ordinary cooling system.

7. Disperse/ Dissolve Phase G materials at 45 degree C, add to Phase ABCDEF and
stir for 5 minutes.

The above clearly reveal the possible forms of the cosmetic /skin lightening formulation involving the stilbene derivative of Formula 1 as an active ingredient/s in effective amounts.

It is thus possible by way of the present invention to provide for a skin lightening agent comprising cis-stilbene derivatives preferably 3,4,3',5'-teramethoxy-cis-stilbene of Formula 1 and skin lightening compositions comprising the same in effective amounts useful for topical application to human skin including leave on and wash-off products.

Advantageously, the selective cis-stilbene derivative of the present advancement is found to be unexpectedly efficacious in inhibiting the synthesis of melanin that is also equally effective in inhibiting the length of dendrite to thus favour superior skin lightening characteristics. The present invention is further directed to cost-effective and safe, natural extract based skin lightening agent for its wide beneficial application and use in cosmetic formulations.

WE CLAIM:

1. A skin lightening agent comprising cis-stilbene derivative as an effective melanin
synthesis inhibition and/or dendrite elongation inhibitory active.

2. A skin lightening agent as claimed in claim 1 wherein said melanin synthesis inhibition and/or dendrite elongation inhibitory active comprising cis-stilbene derivatives comprises 3,4,3',5'-teramethoxy-cis-stilbene of Formula 1 as represented hereunder 3,4,3' ,5'-Tetramethoxystilbene (Formula 1)

3. A skin lightening agent as claimed in anyone of claims 1 or 2 wherein said melanin synthesis inhibition and/or dendrite elongation inhibitory active comprising
cis-stilbene derivatives preferably comprises 3,4,3';5'-teramethoxy-cis-stilbene of
Formula 1 which is either synthesized or sourced from natural renewable plant sources.

4. A skin lightening agent as claimed in anyone of claims 1-3 wherein said active of
Formula 1 inhibits the synthesis of melanin by about 72 % and inhibits the elongation of dendrites by about 100% at the levels of about 5ug/ml.

5. A skin lightening composition for topical use comprising melanin synthesis inhibition and/or dendrite elongation inhibitory active comprising cis-stilbene derivatives as claimed in claims 1-4 and a cosmetically acceptable vehicle with or without other skin benefiting agents.

6. A skin lightening composition for topical use as claimed in claim 5 wherein said
melanin synthesis inhibition and/or dendrite elongation inhibitory active preferably comprises 3, 4, 3', 5'-teramethoxy-cis-stilbene of Formula 1

3,4,3>5'-Tetramethoxystilbene (Formula 1)

7. A skin lightening composition for topical use as claimed in claim 5 or 6 wherein said melanin synthesis inhibition and/or dendrite elongation inhibitory active is comprised in an amount of 0.0001 wt% to 20 wt. % preferably 0.001 wt% to 10 wt% and more preferably and 0.01 wt% to 5 wt%

8. A skin lightening composition for topical use as claimed in anyone of claims 5 to
7 comprising a leave-on or a wash-off product adapted for topical delivery in the forms selected from creams, ointments, emulsions, gels, lotions, oils, sticks, sprays, soaps, packs, wraps, woven or nonwoven wipes, films or patches as a vehicle for topical application of the said skin lightening composition.

9. A skin lightening composition for topical use as claimed in anyone of Claims 5 to
8 wherein said melanin synthesis inhibition and/or dendrite elongation inhibitory active comprises selectively cis-stilbene compounds or preferably 3, 4, 3', 5'-teramethoxy-cis-stilbene of Formula 1, either as a pure compound or as at least one ingredient in the semi pure extract of the reaction mixture or plant extract.

10. A skin lightening agent comprising melanin synthesis and dendrite elongation inhibitory active involving cis-stilbene derivatives preferably of Formula 1 and a skin lightening composition obtained thereof substantially as herein described and illustrated with reference to the accompanying examples.