applicant has found , unexpectedly , that certain arbutin esters have the property of inhibiting the synthesis of melanin and are thus capable of acting on skin pigmentation and marks without toxicity . this is all the more surprising given that the free aromatic hydroxyl function of arbutin , which is important in the enzymatic recognition , is , in these compounds , masked by an ester residue , and given that the depigmenting activity is nevertheless conserved , whereas this same aromatic hydroxyl blocked by a sugar residue such as glucose no longer allows the molecule to retain its depigmenting activity . thus , for example , di - o - β - glucopyranose - 1 , 4 - hydroquinone has no depigmenting activity . it is noted that ep 0 597 776 describes the compounds of the invention and their applications in the cosmetics , pharmaceutical , buccodental or food sectors . however , it does not attribute a depigmenting activity to these compounds . the present invention is directed to the use of the present arbutin esters in and / for the manufacture of a cosmetic and / or dermatological composition as a tyrosinase inhibitor and / or the synthesis of melanin . another embodiment of the invention is a cosmetic and / or dermatological process for depigmenting and / or bleaching human skin , hair or head hair , which consists in applying an ester of formula ( i ) in a physiologically acceptable medium to the skin , hair or head hair . the linear or branched alkyl ( r ) group preferably contains from 6 - 18 carbon atoms . preferably , the rco group , in which r is an alkyl group is selected from hexanoyl , decanoyl , dodecanoyl and hexadecanoyl groups . the term alkenyl ( or alcoylene ) group is understood to refer to an unsaturated group containing ethylenic unsaturation . the alkenyl group preferably contains from 6 - 18 carbon atoms . preferably , the rco group , in which r is an alkenyl group is the oleoyl group . the term alcapolyenyl group is understood to refer to an unsaturated radical containing several ethylenically unsaturated groups , in particular having two or three ethylenically unsaturated groups . the alcapolyenyl group is , in particular , an alcadienyl or alcatrienyl radical and preferably contains from 12 - 20 carbon atoms . the rco group in which r is an alcapolyenyl group is , more particularly , the linoleoyl group . the arbutin monoesters of formula ( i ) include 4 - hexanoyloxyphenyl - β - d - glucose , 4 - decanoyloxyphenyl - β - d - glucose , 4 - dodecanoyloxyphenyl - β - d - glucose , 4 - hexadecanoyloxyphenyl - β - d - glucose , 4 - oleoyloxyphenyl - β - d - glucose and 4 - linoleoyloxyphenyl - β - d - glucose . a mixture of these compounds can also be used . in the depigmenting compositions of the invention , the monoesters of formula ( i ) must be employed in an amount which is effective to ensure the intended result . this amount can range , for example , from 0 . 001 - 10 % and preferably from 0 . 005 - 5 % of the total weight of the composition . the composition containing the compounds of the invention contains a physiologically acceptable medium which is suitable for topical application , i . e . one which is compatible with the skin , the scalp and the hair , and constitutes a bleaching and / or depigmenting , cosmetic and / or dermatological composition for topical application . the composition of the invention may be in any pharmaceutical form normally used for topical application , in particular in the form of an aqueous , aqueous - alcoholic or oily solution , an oil - in - water or water - in - oil or multiple emulsion , an aqueous or oily gel , a liquid , pasty or solid anhydrous product , a two - phase product , a dispersion of oil in an aqueous phase with the aid of spherules , these spherules possibly being polymeric nanoparticles such as nanospheres and nanocapsules or better still lipid vesicles of ionic and / or non - ionic type . the composition may be relatively fluid and have the appearance of a white or colored cream , an ointment , a milk , a lotion , a serum , a paste or a foam . it may optionally be applied to the skin in aerosol form . it may also be in solid form and , for example , in the form of a stick . the composition of the invention may comprise any ingredient conventionally used in the cosmetic or dermatological field , in the usual concentrations . these ingredients are selected , in particular , from fatty substances , preserving agents , gelling agents , fragrances , emulsifiers , water , antioxidants , fillers , active agents ( hydrophilic or lipophilic ), screening agents and mixtures thereof . suitable fatty substances , which may be used in the invention , include mineral oils ( liquid petroleum jelly ), oils of plant origin , oils of animal origin , synthetic oils ( isopropyl myristate ), cetylstearyl 2 - ethylhexanoate , silicone oils and fluorinated oils . fatty alcohols ( 2 - hexyl - 1 - decyl alcohol , cetyl alcohol ), fatty acids ( stearic acid ) and waxes , and mixtures thereof , may also be used . suitable emulsifiers which can be used in the invention , include , for example , fatty acid esters of polyethylene glycol , such as polyethylene glycol stearates , and fatty acid esters of glycerol , such as glyceryl stearate , and mixtures thereof . mention may be made , for example , of a mixture of peg - 100 stearate and glyceryl stearate , sold under the name arlacel 165 by the company ici . suitable hydrophilic gelling agents include , in particular , carboxyvinyl polymers ( carbomer ), acrylic copolymers such as acrylate / alkylacrylate copolymers , polyacrylamides , polysaccharides , natural gums and clays . suitable lipophilic gelling agents include modified clays such as bentones , metal salts of fatty acids , hydrophobic silica and polyethylenes . suitable moisturizers include polyols ( glycerol , propylene glycol ), vitamins , keratolytic agents and / or desquamating agents ( salicylic acid and its derivatives , α - hydroxy acids , ascorbic acid and its derivatives ), anti - inflammatory agents , calmants and mixtures thereof . in the event of incompatibility , these active agents can be incorporated into spherules , in particular ionic or non - ionic vesicles and / or nanoparticles ( nanocapsules and / or nanospheres ), so as to isolate them from each other in the composition . one test demonstrates the activity of compounds of the invention as depigmenting agents , compared with the activity of kojic acid . the test is conducted on a co - culture of keratinocytes and melanocytes by the procedure described in patent application fr 2 , 734 , 825 filed by the applicant , and in the article by r . schmidt , p . krim and m . requin , analyses biochimiques 235 ( 2 ), 113 - 18 , ( 1996 ). for each test compound , the ic 50 value , i . e . the micromolar concentration ( μm ) for which 50 % inhibition of melanogenesis is observed , is determined . the arbutin presents in this test , an ic50 equivalent to kojic acid . this table shows that the compounds of formula ( i ) of the invention are more effective than kojic acid . in addition , they have the advantage of having no cytotoxicity with regard to keratinocytes and melanocytes , which is the major fault of the existing depigmenting agents . having generally described this invention , a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only and are not intended to be limiting unless otherwise specified . the concentrations are given as a percentage by weight . when applied daily , the cream obtained allows the skin to be bleached . the disclosure of priority french application no . 9708674 filed jul . 8 , 1997 is hereby incorporated by reference into the present application . obviously , numerous modifications and variations of the present invention are possible in light of the above teachings . it is , therefore , to be understood that within the scope of the appended claims , the invention may be practiced otherwise than as specifically described herein .
arbutin monoesters are employed in a composition for topical application , as a depigmenting and / or bleaching agent for human skin , hair and / or head hair . the invention relates to a method of manufacturing a composition of at least one arbutin monoester in a physiologically acceptable medium for depigmenting and / or bleaching human skin , hair and / or head hair .