unless otherwise indicated , numeric ranges , for instance as in “ from 2 to 10 ,” are inclusive of the numbers defining the range ( e . g ., 2 and 10 ). unless otherwise indicated , ratios , percentages , parts , and the like are by weight . “ room temperature ,” as used in this specification , is the ambient temperature , for example , 20 - 25 ° c . “ alkyl ,” as used in this specification , encompasses straight and branched chain aliphatic hydrocarbon groups having the indicated number of carbon atoms . if no number is indicated , then 1 - 6 alkyl carbons are contemplated . unless otherwise indicated , the alkyl group is optionally substituted with 1 , 2 , or 3 , preferably 1 or 2 , more preferably 1 , substituents that are compatible with the syntheses described herein . such substituents include , but are not limited to , nitro , halogen , carboxylic acids ( e . g ., c 0 - c 6 — cooh ), c 2 - c 6 alkene , cyano , amido , and / or ester . unless otherwise indicated , the foregoing substituent groups are not themselves further substituted . as noted above , in one aspect the invention provides a compound of formula i . in another aspect , the invention provides a composition comprising a compound of formula i and a dermatologically acceptable carrier . in some embodiments , at least three of r 1 , r 2 , r 3 , r 4 , r 5 , r 6 , r 7 , r 8 , r 9 , and r 10 in the compounds of formula i are — oh . in some embodiments , at least four of r 1 , r 2 , r 3 , r 4 , r 5 , r 6 , r 7 , r 8 , r 9 , and r 10 in the compounds of formula i are — oh . in some embodiments , at least two of r 6 , r 7 , r 8 , r 9 , or r 10 are — oh . in some embodiments , r 8 is — oh , and at least one of r 6 , r 7 , r 9 or r 10 is — oh . in some embodiments , r 8 is — oh , at least one of r 6 , r 7 , r 9 or r 10 is — oh , and none of r 1 , r 2 , r 3 , r 4 , r 5 , r 6 , r 7 , r 9 , or r 10 are c 1 - c 6 alkoxy . in some embodiments , at least one of r 1 or r 5 is — oh . in some embodiments , at least one of r 6 , r 8 , or r 10 is — oh . in some embodiments , r 2 and / or r 4 is h , oh , or c 1 - c 6 alkoxy ( preferably methoxy ). in some embodiments of the composition of the invention , the compound of formula i is as shown in table 1 : a person of ordinary skill in the art can readily determine the effective amount of the antioxidant compound of formula i that should be used in a particular composition in order to provide the benefits described herein ( e . g ., free radical scavenging and inhibition of collagen degradation ), via a combination of general knowledge of the applicable field as well as routine experimentation where needed . by way of non - limiting example , the amount of the compound of formula i in the composition of the invention may be in the range of from 0 . 01 to 5 weight percent , preferably from 0 . 05 to 3 weight percent , and more preferably from 0 . 1 to 1 weight percent , based on the total weight of the composition . compounds of formula i may be readily prepared by those skilled in the art using known synthetic techniques . for instance , the compounds may be prepared by the reaction of a phenyl aldehyde compound ( containing one or more hydroxyl groups on the phenyl , such as 4 - hydroxybenzaldehyde ) with a phenylhydroxylamine compound ( also containing one or more hydroxyl groups on the phenyl , such as 3 , 4 - dihydroxybenzylhydroxylamine ), followed by isolation and purification of the desired product . compositions of the invention also include a dermatologically acceptable carrier . such material is typically characterized as a carrier or a diluent that does not cause significant irritation to the skin and does not negate the activity and properties of active agent ( s ) in the composition . examples of dermatologically acceptable carriers that are useful in the invention include , without limitation , emulsions , creams , aqueous solutions , oils , ointments , pastes , gels , lotions , milks , foams , suspensions , powders , or mixtures thereof . in some embodiments , the composition contains from about 99 . 99 to about 50 percent by weight of the dermatologically acceptable carrier , based on the total weight of the composition . the dermatologically acceptable carrier of the invention may also include , for instance , water , a thickener , an emollient , an emulsifier , a humectant , a surfactant , a suspending agent , a film forming agent , a foam building agent , a preservative , an antifoaming agent , a fragrance , a lower monoalcoholic polyol , a high boiling point solvent , a propellant , a colorant , a pigment , glycerin , a mineral oil , silicon feel modifiers , preservatives , emollients , or mixtures thereof . other additives may be included in the compositions of the invention such as , but not limited to , abrasives , absorbents , aesthetic components such as fragrances , pigments , colorings / colorants , essential oils , skin sensates , astringents ( e . g ., clove oil , menthol , camphor , eucalyptus oil , eugenol , menthyl lactate , witch hazel distillate ), anti - caking agents , antifoaming agents , antimicrobial agents ( e . g ., iodopropyl butylcarbamate ), other antioxidants , binders , biological additives , buffering agents , bulking agents , chelating agents , chemical additives , colorants , cosmetic astringents , cosmetic biocides , denaturants , drug astringents , external analgesics , film formers or materials , e . g ., polymers , for aiding the film - forming properties and substantivity of the composition ( e . g ., copolymer of eicosene and vinyl pyrrolidone ), opacifying agents , ph adjusters , propellants , reducing agents , sequestrants , skin bleaching and lightening agents ( e . g ., hydroquinone , kojic acid , ascorbic acid , magnesium ascorbyl phosphate , ascorbyl glucosamine ), skin - conditioning agents ( e . g ., humectants , including miscellaneous and occlusive ), skin soothing and / or healing agents ( e . g ., panthenol and derivatives ( e . g ., ethyl panthenol ), aloe vera , pantothenic acid and its derivatives , allantoin , bisabolol , and dipotassium glycyrrhizinate ), skin treating agents , thickeners , and vitamins ( e . g ., vitamin c ) and derivatives thereof . the composition of the invention may be , for example , in the form of an oil , a gel , a solid stick , a lotion , a cream , a milk , an aerosol , a spray , a foam , a mousse , an ointment or a fatty ointment or a powder . compositions of the invention may be used in a variety of personal care applications , such as in cosmetics and in skin care ( e . g ., lotions , creams , oils , topical medicines , and sunscreens ). the compositions of the invention may be manufactured by processes well known in the art , e . g ., by means of conventional mixing , dissolving , granulating , emulsifying , encapsulating , entrapping or lyophilizing processes . as noted above , compositions of the invention , containing a compound of formula i , are highly effective as radical scavengers . they exhibit significantly better antioxidant attributes compared to previously known antioxidants for personal care applications . furthermore it has been found that the performance of nitrones that have phenolic groups cannot be achieved by simply adding two different antioxidants , one with a phenolic functionality and another with nitrone functionality . rather , the presence of both functionalities in the same molecule is an important aspect of their favorable performance . the cosmetic compositions of the invention are useful for the treatment and protection of skin from free radicals caused , for instance , by exposure to ultraviolet light , such as uva and uvb rays , as well as other harmful forms of radiation , such as long wave infrared . thus , for instance , the cosmetic compositions may be used in a method for inhibiting the degradation of collagen . according to such method , an effective amount of the composition may be topically administering to skin in need of such treatment . the compositions may also be used in a method for reducing the visible signs of aging , which may result from the radical induced degradation of collagen in the skin , by applying to skin in need of such treatment the composition . visible signs of aging may include , for instance , development of textural discontinuities such as wrinkles and coarse deep wrinkles , skin lines , crevices , bumps , large pores , or unevenness or roughness , reducing fine lines , loss of skin elasticity ( loss and / or inactivation of functional skin elastin ), sagging ( including puffiness in the eye area and jowls ), loss of skin firmness , loss of skin tightness , loss of skin recoil from deformation , discoloration ( including undereye circles ), blotching , sallowness , hyperpigmented skin regions such as age spots and freckles , keratoses , abnormal differentiation , hyperkeratinization , elastosis , and other histological changes in the stratum corneum , dermis , epidermis , the skin vascular system ( e . g ., telangiectasia or spider vessels ), and underlying tissues , especially those proximate to the skin . in practicing the methods of the invention , the cosmetic composition are generally administered topically by applying or spreading the compositions onto the skin . a person of ordinary skill in the art can readily determine the frequency with which the cosmetic compositions should be applied . the frequency may depend , for example , on the amount of sunlight that an individual is likely to encounter in a given day and / or the sensitivity of the individual to sunlight . by way of non - limiting example , administration on a frequency of at least once per day may be desirable . some embodiments of the invention will now be described in detail in the following examples . a 100 ml 3 - neck flask was equipped with a magnetic stirrer , a reflux condenser , an addition funnel , a thermocouple , an ice bath , and a nitrogen blanket . the flask was charged with 13 . 81 grams ( 0 . 10 moles ) of 3 , 4 - dihydroxybenzaldehyde and with 50 ml of 100 % ethanol . the mixture was stirred at room temperature under nitrogen to give a clear dark brown solution . the solution was cooled to & lt ; 15 ° c . the addition funnel was charged with 6 . 63 grams ( 0 . 10 moles ) of 50 wt . % aqueous hydroxylamine solution . the hydroxylamine solution was added to the cooled aldehyde solution over a period of about 45 minutes . during the addition , the reaction mixture temperature was maintained at & lt ; 20 ° c . after completing the hydroxylamine solution addition , the reaction mixture was heated at 55 ° c . until gc analysis showed that the aldehyde was essentially gone ( about 7 hours ). the reaction mixture was solvent - stripped by rotary evaporation to give a quantitative yield of the oxime as a brown solid . m . p .= 161 - 163 ° c . gc showed & gt ; 98 % purity . structure was confirmed by ir , nmr , and gc / ms analyses . a 125 ml 3 - neck flask was equipped with a magnetic stirrer , a sintered glass sparging tube , a ph electrode with meter , and a claisen adapter fitted with a thermocouple and a gas outlet . the flask was charged with 4 . 59 grams ( 0 . 03 moles ) of the 3 , 4 - dihydroxybenzaldehyde oxime ( 34dhbzox ) from above and with 40 ml of methanol . the mixture was stirred at room temperature to give a clear brown solution . sodium cyanoborohydride ( 1 . 89 grams , 0 . 03 moles ) was then added to the oxime solution in one portion . a lecture bottle of hydrogen chloride gas was connected to the sparging tube with a safety trap in between . the hcl bottle was opened just enough to allow a trickle of gas to sparge into the reaction mixture . the ph of the mixture dropped quickly from about 7 to & lt ; 3 . at the same time , the reaction mixture foamed vigorously and solids began to precipitate . sparging with hcl was stopped , and the ph was monitored . after the ph had stabilized at & lt ; 3 for 1 hour , the reaction mixture was filtered and the white solids were washed on the filter with small portions of methanol . after drying , 1 . 38 grams of white solid were obtained . the filtrate and methanol washings were combined , and the solvent was removed by rotary evaporation to give 6 . 27 grams of beige solids . these solids were combined with the solids obtained by filtration , and were dissolved in about 25 ml of water to give a clear brown solution having ph about 5 . the ph was increased to about 8 by the addition of a saturated aqueous solution of sodium bicarbonate . at this point , solids began to separate out . the mixture was cooled in an ice bath for about 1 hour , then it was filtered . the solids were washed on the filter with portions of water . after drying under vacuum at 55 ° c . for about 1 hour , the yield of hydroxylamine as a dark brown solid was 2 . 56 grams ( 55 % yield ). mp = 149 - 151 ° c . the structure was confirmed by ir and nmr analyses . hplc analysis gave a purity of & gt ; 75 %. a 500 ml 1 - neck flask was equipped with a magnetic stirrer and a septum . the flask was charged with 7 . 76 grams ( 0 . 05 moles ) of 3 , 4 - dihydroxybenzylhydroxylamine , 175 ml of methanol , and 7 . 61 grams ( 0 . 05 moles ) of vanillin . the reaction mixture was stirred at room temperature for 2 days . the solvent was removed from the reaction mixture by rotary evaporation to give 14 . 52 grams of light brown solid product ( 100 % of theory ). mp = about 129 ° c . to & gt ; 150 ° c . hplc analysis gave a purity of about 94 %. a 4 . 22 gram sample of the crude product was purified by column chromatography on 115 grams of silica gel 60 , using ethyl acetate - methanol ( 95 : 5 , v / v ) as the eluting solvent system . the column fractions were monitored by tlc . the yield of purified product obtained was 1 . 10 grams ( 26 % based on amount charged to the column ). mp = 190 - 191 ° c . structure was confirmed by ir , nmr , and gc / ms analyses . hplc analysis gave a purity of & gt ; 99 %. a 250 ml 1 - neck flask was equipped with a magnetic stirrer and a septum . the flask was charged with 3 . 88 grams ( 0 . 025 moles ) of 3 , 4 - dihydroxybenzylhydroxylamine , 75 ml of methanol , and 3 . 05 grams ( 0 . 025 moles ) of salicylaldehyde . the reaction mixture was stirred at room temperature for 3 days . the solvent was removed from the reaction mixture by rotary evaporation to give 11 . 86 grams of dark brown tarry product ( 180 % of theory ). the crude product was stirred at room temperature with 100 ml of methanol ; not all of the product dissolved . the mixture was filtered . the solvent was removed from the filtrate by rotary evaporation to give 7 . 59 grams of brown solid product ( 117 % of theory ). hplc analysis showed about 87 area % product with both higher and lower molecular weight impurities also present . a 4 . 15 gram sample of the crude product was purified by column chromatography on 100 grams of silica gel 60 , using ethyl acetate - methanol ( 95 : 5 , v / v ) as the eluting solvent system . the column fractions were monitored by tlc . the yield of purified product obtained was 1 . 51 grams ( 36 % based on amount charged to the column ). mp = 157 - 161 ° c . structure was confirmed by ir , nmr , and gc / ms analyses . a 100 ml 1 - neck flask was equipped with a magnetic stirrer and a rubber septum . the flask was charged with 1 . 05 grams ( 0 . 0068 moles ) of 4 -(( hydroxyamine ) methyl ) benzene - 2 , 4 - diol , 1 . 1 grams ( 0 . 0072 moles ) of vanillin , and 20 ml of methanol . not all of the solids dissolved , even after heating at 50 ° c . for 2 hours . the mixture was stirred at room temperature for 3 days . the mixture was filtered , and the solids were washed on the filter with a little methanol . after drying in air for several hours , the yield of product was 1 . 7 grams ( 87 % yield ). mp = 175 - 177 ° c . structure was confirmed by ir and nmr analyses . a 100 ml 1 - neck flask was equipped with a magnetic stirrer and a rubber septum . the flask was charged with 1 . 6 grams ( 0 . 01 moles ) of p - hydroxybenzylhydroxyamine hydrochloride , 0 . 36 grams ( 0 . 1 moles ) of sodium hydroxide pellets , and 10 ml of methanol . as the mixture was stirred at room temperature , sodium chloride began to precipitate . water was added until a homogeneous solution was obtained . about 4 ml were required . the p - hydroxy benzaldehyde ( 1 . 2 grams , 0 . 01 moles ) was then added , and the clear solution was heated at 60 ° c . for 6 hours . the mixture was then stirred at room temperature for 3 days . the resulting white slurry was filtered , and the solids were washed on the filter with a little water . after drying under vacuum at 35 ° c ., the yield of product was 1 . 8 grams ( 79 . 3 % yield ). mp = 196 - 196 ° c . structure was confirmed by ir and nmr analyses . a 100 ml 1 - neck flask was equipped with a magnetic stirrer and a rubber septum . the flask was charged with 1 . 55 grams ( 0 . 01 moles ) of 2 , 4 - dihydroxybenzylhydroxlamine , 1 . 06 grams ( 0 . 01 moles ) of benzaldehyde , 10 ml of methanol , and 2 ml of water . the mixture was stirred at 50 ° c . for 2 hours , yielding a clear brown solution . the mixture was stirred at room temperature overnight . the resulting slurry was filtered . the solids were washed on the filter with a little warm water , then they were dried under vacuum at 35 ° c . the yield of product was 1 . 65 grams ( 67 . 9 % yield ). mp = 158 ° c . structure was confirmed by ir and nmr analyses . a 100 ml 1 - neck flask was equipped with a magnetic stirrer and a rubber septum . the flask was charged with 1 . 39 grams ( 0 . 01 moles ) of p - hydroxybenzylhydroxlamine , 1 . 06 grams ( 0 . 01 moles ) of benzaldehyde , 10 ml of methanol , and 2 ml of water . the mixture was heated at 50 ° c . for 6 hours , and then it was stirred at room temperature overnight . the resulting white slurry was filtered , and the solids were washed on the filter with a small amount of water . the solids were dried under vacuum at 35 ° c . the yield of product was 1 . 8 grams ( 79 % yield ). mp = 191 ° c . structure was confirmed by ir and nmr analyses . a 100 ml 1 - neck flask was equipped with a magnetic stirrer and a rubber septum . the flask was charged with 1 . 55 grams ( 0 . 01 moles ) of 2 , 4 - dihydroxybenzylhydroxylamine , 1 . 38 grams ( 0 . 01 moles ) of 2 , 4 - dihydroxybenzaldehyde , 10 ml of methanol , and 2 ml of water . the mixture was heated at 50 ° c . for 6 hours , and then it was stirred at room temperature overnight . the resulting white slurry was filtered , and the solids were washed on the filter with a small amount of water . the solids were dried under vacuum at 35 ° c . the yield of product was 2 . 4 grams ( 87 % yield ). mp = 203 - 204 ° c . structure was confirmed by ir and nmr analyses . antioxidant potential is evaluated using the oxygen radical absorbance capacity ( orac ) protocol . orac is a chemical in - vitro method based on the hydrogen atom transfer ( hat ) mechanism ( see n . re et al ., free radical biology & amp ; medicine , 26 ( 9 / 10 ), 1231 ( 1997 )). orac measures antioxidant inhibition of peroxyl radical induced oxidations and thus reflects classical radical chain breaking antioxidant activity by h atom transfer . in this assay , the peroxyl radical reacts with a fluorescent probe to form a non - fluorescent product . this is quantitated using a fluorescence measurement . antioxidant capacity is determined by decreased rate and amount of product formed over time . this assay depends upon the free radical damage to the fluorescent probe resulting in the change in its fluorescence intensity . the change of fluorescence intensity is an indicator of the degree of free radical damage . in the presence of an antioxidant , the inhibition of free radical damage is reflected in higher fluorescence intensity and can be measured as antioxidant capacity against the free radicals . the uniqueness of orac assay is that the reaction is driven to completion . this allows calculation of the area under the curve ( auc ) and gives an absolute quantitation of antioxidancy as opposed to relative measurements in many other assays . as noted , the longer it takes to observe a decrease in fluorescence , the higher the antioxidant ( ao ) potential . from the auc for a given antioxidant , the auc for blank is subtracted to give its orac value . the concentration of ao needed to give the same auc values as trolox is calculated and used to represent the trolox equivalent ao capacity ( teac ). trolox is ((±)- 6 - hydroxy - 2 , 5 , 7 , 8 - tetramethylchromane - 2 - carboxylic acid , cas # 53188 - 07 - 1 ), and is used as an internal control . the orac test is conducted in the compounds of table 1 above ( inventive compounds ) as well as to vitamin c , vitamin e , and the following comparative compounds : the inventive nitrones in the orac test solutions were at a concentration of 30 micromolar , while the concentrations of trolox , vitamin c , vitamin e , bht , pbn + bht , and val - ipha were at 100 micromolar . the teac values calculated from the orac values are listed the table 2 . surprisingly , it is found that the compounds of the invention displayed significantly higher orac values compared to the known antioxidants vitamin e or c . it is also evident that the teac values of phenolic aos such as bht , a non - aromatic nitrone such as val - ipha , or an aromatic nitrone such as pbn are not very high compared to the teac values of the compounds of the invention , which contain both phenolic and nitrone moieties in a polyhydroxy stilbenoid mimic structure . the teac value for a physical blend of an aromatic nitrone and a phenolic ao ( pbn + bht ) is relatively small also . this leads us to believe that for the regenerative mechanism to take place , the nitrone and the phenolic functionalities need to be part of the same molecule .
provided are compounds and compositions thereof that are useful as antioxidants in personal care formulations . the compounds are of the formula i : wherein r 1 , r 2 , r 3 , r 4 , r 5 , r 6 , r 7 , r 8 , r 9 , and r 10 are independently h , c 1 - c 10 alkyl , — oh , c 1 - c 6 alkoxy , — cooh , — coo − m + , or — o − m + , where m + is a sodium , potassium , or ammonium ion , provided that at least one of r 6 , r 7 , r 8 , r 9 , or r 10 is — oh .