A composition comprising the following compounds: i) a compound of formula, wherein: R 1 is a radical selected from the group consisting of: (C 1 -C 8)-alkyl and R 2 OR 3; R 2 is a (C 1 -C 4)-alkenyl bi-radical; and R 3 is a radical selected from the group consisting of: (C 1 -C 4)-alkyl, phenyl; and phenyl substituted by a (C 1 -C 4)-alkyl; ii) a compound of formula, wherein: R 4 is a radical selected from the group consisting of: (C 1 -C 10)-alkyl; (C 1 -C 10)-alkyl substituted by one or two hydroxyls; CH 2 -(C 1 -C 9)-alkyl, wherein one or two carbons of the (C 1 -C 9) portion is a CO radical; phenyl; phenyl substituted by a hydroxyl and by a CHO; and phenyl substituted by two radicals independently selected from the group consisting of: (C 1 -C 4)-alkyl and hydroxyl. iii) a compound of formula, wherein: R 5 is a bi-radical selected from the group consisting of: (C 1 -C 10)-alkyl; (C 1 -C 10)-alkyl substituted by a hydroxyl; R 6 is a radical selected from the group consisting of hydrogen and (C 1 -C 5)-alkyl; n is an integer from 0 to 1, with the proviso that: i) when R 5 is hydrogen, then n is 0; and ii) when R 6 is (C 1 -C 5)-alkyl, then R 5 is hydrogen and n is 0; Y is a radical selected from the group consisting of: phenyl; (C 3 -C 6)-cycloalkyl; phenyl substituted by a radical selected from the group consisting of: OR 6, COOR 7, CONHR 8, CN and hydroxyl; (C 3 -C 6)-cycloalkyl substituted by a radical selected from the group consisting of: OR 7, COOR 8, CONHR 9, CN and hydroxyl; and OR 10; R 7 is a (C 1 -C 3)-alkyl; R 8 and R 9 are radicals independently selected from the group consisting of (C 1 -C 3)-akyl and hydrogen; and R 10 is a radical selected from the group consisting of: hydrogen and acryloyl. i) a compound of formula, wherein: R 1 is a radical selected from the group consisting of: (C 1 -C 8)-alkyl and R 2 OR 3; R 2 is a (C 1 -C 4)-alkenyl bi-radical; and R 3 is a radical selected from the group consisting of: (C 1 -C 4)-alkyl, phenyl; and phenyl substituted by a (C 1 -C 4)-alkyl; R 1 is a radical selected from the group consisting of: (C 1 -C 8)-alkyl and R 2 OR 3; R 2 is a (C 1 -C 4)-alkenyl bi-radical; and R 3 is a radical selected from the group consisting of: (C 1 -C 4)-alkyl, phenyl; and phenyl substituted by a (C 1 -C 4)-alkyl; ii) a compound of formula, wherein: R 4 is a radical selected from the group consisting of: (C 1 -C 10)-alkyl; (C 1 -C 10)-alkyl substituted by one or two hydroxyls; CH 2 -(C 1 -C 9)-alkyl, wherein one or two carbons of the (C 1 -C 9) portion is a CO radical; phenyl; phenyl substituted by a hydroxyl and by a CHO; and phenyl substituted by two radicals independently selected from the group consisting of: (C 1 -C 4)-alkyl and hydroxyl. R 4 is a radical selected from the group consisting of: (C 1 -C 10)-alkyl; (C 1 -C 10)-alkyl substituted by one or two hydroxyls; CH 2 -(C 1 -C 9)-alkyl, wherein one or two carbons of the (C 1 -C 9) portion is a CO radical; phenyl; phenyl substituted by a hydroxyl and by a CHO; and phenyl substituted by two radicals independently selected from the group consisting of: (C 1 -C 4)-alkyl and hydroxyl. iii) a compound of formula, wherein: R 5 is a bi-radical selected from the group consisting of: (C 1 -C 10)-alkyl; (C 1 -C 10)-alkyl substituted by a hydroxyl; R 6 is a radical selected from the group consisting of hydrogen and (C 1 -C 5)-alkyl; n is an integer from 0 to 1, with the proviso that: i) when R 5 is hydrogen, then n is 0; and ii) when R 6 is (C 1 -C 5)-alkyl, then R 5 is hydrogen and n is 0; Y is a radical selected from the group consisting of: phenyl; (C 3 -C 6)-cycloalkyl; phenyl substituted by a radical selected from the group consisting of: OR 6, COOR 7, CONHR 8, CN and hydroxyl; (C 3 -C 6)-cycloalkyl substituted by a radical selected from the group consisting of: OR 7, COOR 8, CONHR 9, CN and hydroxyl; and OR 10; R 7 is a (C 1 -C 3)-alkyl; R 8 and R 9 are radicals independently selected from the group consisting of (C 1 -C 3)-akyl and hydrogen; and R 10 is a radical selected from the group consisting of: hydrogen and acryloyl. R 5 is a bi-radical selected from the group consisting of: (C 1 -C 10)-alkyl; (C 1 -C 10)-alkyl substituted by a hydroxyl; R 6 is a radical selected from the group consisting of hydrogen and (C 1 -C 5)-alkyl; n is an integer from 0 to 1, with the proviso that: i) when R 5 is hydrogen, then n is 0; and ii) when R 6 is (C 1 -C 5)-alkyl, then R 5 is hydrogen and n is 0; Y is a radical selected from the group consisting of: phenyl; (C 3 -C 6)-cycloalkyl; phenyl substituted by a radical selected from the group consisting of: OR 6, COOR 7, CONHR 8, CN and hydroxyl; (C 3 -C 6)-cycloalkyl substituted by a radical selected from the group consisting of: OR 7, COOR 8, CONHR 9, CN and hydroxyl; and OR 10; R 7 is a (C 1 -C 3)-alkyl; R 8 and R 9 are radicals independently selected from the group consisting of (C 1 -C 3)-akyl and hydrogen; and R 10 is a radical selected from the group consisting of: hydrogen and acryloyl.