Stabilization of thiopyridinone compound and composition comprising same

A method comprising:

• adding (2) caffeine in a composition comprising (1) at least one compound selected from compounds of formula (I) below, tautomers of formula (I′) below, salts thereof, solvates, such as hydrates, thereof, optical isomers thereof, racemates thereof, and mixtures thereof:
• in which
• R1 denotes a radical chosen from
• a) a hydrogen atom, and
• b) a saturated, linear C1-C10 or branched C3-C10 alkyl group optionally substituted with one or more groups, which may be identical or different, chosen from
• i) —O—R3, and
• ii) —S—R3,
• and
• R2 denotes a radical chosen from
• a) a hydrogen atom,
• b) a saturated, linear C1-C12 or branched C3-C12 or cyclic C3-C8 hydrocarbonated group optionally substituted with one or more groups, which may be identical or different, chosen from
• i) —O—R3,
• ii) —S—R3,
• iii) —C(O)—O—R3, and
• iv) a C5-C12 aryl group optionally substituted with one or more hydroxyls and/or with one or more C1-C8 alkoxy radicals, and
• c) a C5-C12 aryl group optionally substituted with one or more hydroxyls and/or with one or more C1-C8 alkoxy radicals
• wherein
• R3 denotes a radical chosen from
• a) a hydrogen atom, and
• b) a saturated, linear C1-C10 or branched C3-C10 alkyl group in order to photostabilize the (1) compound(s).