Methods and compositions for inhibiting free radical polymerization in skin and hair

Abstract

A method is provided for inhibiting free radical degradation in the skin of a human or nonhuman animal comprising contacting the skin with a skin treatment composition having a concentration of a 1-(3-methoxybenzyl)-3-substituted thiourea compound effective for inhibiting free radical generation. Skin protecting compositions comprising a free radical inhibiting concentration of a 1-(3-methoxybenzyl)-3-substituted thiourea compound, and optionally a sunscreeen composition, are also provided.

We claim:  
     
         1 . A method for inhibiting free radical degradation of skin or hair of a human or nonhuman animal comprising contacting the skin or hair with a composition comprising a 1-(3-methoxybenzyl)-3-substituted thiourea compound of formula I  
       
         
           
           
               
               
           
         
       
       in a concentration which is effective to inhibit free radical polymerization, wherein R is selected from the group consisting of C 1 -C 20  linear or branched alkyl; C 5 -C 7  cycloalkyl; alkoxy-substituted C 5 -C 7  cycloalkyl; hydroxy-substituted C 5 -C 7  cycloalkyl; C 6 -C 7  aryl; hydroxy-substituted C 6 -C 7  aryl; and alkoxy-substituted C 6 -C 7  aryl.  
     
     
         2 . A method according to  claim 1  wherein the composition comprises between about 0.01% and 5% by weight of a compound of formula I.  
     
     
         3 . A method according to  claim 2  wherein the composition comprises between about 0.1% and 2% by weight of a compound of formula I.  
     
     
         4 . A method according to  claim 1  wherein the composition comprises an oil that contains at least one compound of formula I.  
     
     
         5 . A method according to  claim 4  wherein the composition is an emulsion.  
     
     
         6 . A method according to  claim 4  wherein the oil is meadowfoam seed oil.  
     
     
         7 . A method according to  claim 1  wherein R is selected from the group consisting of (i) C 1 -C 20  linear alkyl, (ii) hydroxy-substituted C 6 -C 7  aryl and (iii) alkoxy-substituted C 6 -C 7  aryl moieties.  
     
     
         8 . A method according to  claim 1  wherein the compound of formula I is selected from the group consisting of 1,3-di(3-methoxybenzyl) thiourea; 1-(3-methoxybenzyl)-3-ethyl-2-thiourea; 1-(3-methoxybenzyl)-3-propyl-2-thiourea; 1-(3-methoxybenzyl)-3-hexyl-2-thiourea; 1-(3-methoxybenzyl)-3-dodecyl-2-thiourea; 1-(3-methoxybenzyl)-3-(4-hydroxyphenyl)-2-thiourea; and 1-(3-methoxybenzyl)-3-(3-methoxyphenyl)-2-thiourea.  
     
     
         9 . A method according to  claim 1  wherein the compound of formula I is 1,3-di(3-methoxybenzyl) thiourea.  
     
     
         10 . A method according to  claim 1  wherein the composition is a skin treatment composition.  
     
     
         11 . A method according to  claim 1  wherein the composition is hair treatment composition.  
     
     
         12 . A composition for inhibiting free radical degradation of skin or hair of a human or nonhuman animal comprising a base composition and an amount of a 1-(3-methoxybenzyl)-3-substituted thiourea compound of formula I  
       
         
           
           
               
               
           
         
       
       which is sufficient to provide a concentration of the compound of formula I effective to inhibit free radical polymerization, wherein R is selected from the group consisting of C 1 -C 20  linear or branched alkyl; C 5 -C 7  cycloalkyl; alkoxy-substituted C 5 -C 7  cycloalkyl; hydroxy-substituted C 5 -C 7  cycloalkyl; C 6 -C 7  aryl; hydroxy-substituted C 6 -C 7  aryl; and alkoxy-substituted C 6 -C 7  aryl.  
     
     
         13 . A composition according to  claim 12  which comprises between about 0.01% and 5% by weight of a compound of formula I.  
     
     
         14 . A composition according to  claim 12  which comprises between about 0.1% and 2% by weight of a compound of formula I.  
     
     
         15 . A composition according to  claim 12  which comprises an oil that contains at least one compound of formula I.  
     
     
         16 . A composition according to  claim 15  wherein the composition is an emulsion.  
     
     
         17 . A composition according to  claim 15  wherein the oil is meadowfoam seed oil.  
     
     
         18 . A composition according to  claim 12  wherein R is selected from the group consisting of (i) C 1 -C 20  linear alkyl, (ii) hydroxy-substituted C 6 -C 7  aryl and (iii) alkoxy-substituted C 6 -C 7  aryl moieties.  
     
     
         19 . A composition according to  claim 12  which is selected from the group consisting of 1,3-di(3-methoxybenzyl) thiourea; 1-(3-methoxybenzyl)-3-ethyl-2-thiourea; 1-(3-methoxybenzyl)-3-propyl-2-thiourea; 1-(3-methoxybenzyl)-3-hexyl-2-thiourea; 1-(3-methoxybenzyl)-3-dodecyl-2-thiourea; 1-(3-methoxybenzyl)-3-(4-hydroxyphenyl)-2-thiourea; and 1-(3-methoxybenzyl)-3-(3-methoxyphenyl)-2-thiourea.  
     
     
         20 . A composition according to  claim 12  which is a skin treatment composition.  
     
     
         21 . A composition according to  claim 12  which is a hair treatment composition.  
     
     
         22 . A composition according to  claim 12  which further comprises an effective concentration of a sunscreen compound.  
     
     
         23 . A composition according to  claim 12  wherein the compound of formula I is 1,3-di(3-methoxybenzyl) thiourea.  
     
     
         24 . A composition according to  claim 22  which comprises an oil containing the compound of formula I.  
     
     
         25 . A composition according to  claim 24  wherein the composition is an emulsion.  
     
     
         26 . A composition according to  claim 24  wherein the oil is meadowfoam seed oil.  
     
     
         27 . A composition according to  claim 24  which further comprises an effective concentration of a sunscreen compound.