The present invention relates to a composition, which comprises a) an organic material susceptible to oxidative, thermal or light-induced degradation, which is a polymer, an oligohydroxy compound, a wax, a fat or a mineral oil, with the proviso that the polymer is not a polypeptide, agar-agar or a component of agar-agar and the oligohydroxy compound is not glucose or a component of agar-agar; and b) a compound of formula (I) n is 1, 2, 3 or 4; when n is 1, R5 is H, C1-C30-alkyl, C3-C10-cycloalkyl, C6-C10-aryl, which is unsubstituted or substituted by C1-C8-alkyl, C1-C8-alkoxy, halogen or one phenyl, C7-C13-aralkyl, C2-C22-alkenyl, C3-C12-alkinyl, OH, C1-C30-alkyloxy, C3-C10-cycloalkyloxy, C6-C12-aryloxy, C7-C13-aralkyloxy, hydroxy-C1-C8-alkyl, carboxy-C1-C12-alkyl, C1-C12-alkoxycarbonyl-C1-C12-alkyl, C2-C30-alkyl, which is interrupted by one or more oxygen atoms, C2-C16-alkyl, which is interrupted by one sulfur atom, or NR′1R′2; when n is 2, R5 is C1-C12-alkane-diyl, C6-C14-arylene, C4-C8-cycloalkane-bis-(C1-C4-alkylene), C6-C14-arene-bis-(C1-C4-alkylene), C4-C24-alkane-diyl, which is interrupted by one or more oxygen atoms, C4-C20-alkane-diyl, which is interrupted by one or more —NH—, —N(C1-C8-alkyl)- or —N(hydroxy-C1-C8-alkyl)-, piperazine-N,N′-bis-(C1-C4-alkylene) or C2-C10-alkane-diyl, which is interrupted by one sulfur atom; R1 to R4 and R6 to R9 are each independently from each other H, C1-C12-alkyl, C3-C10-cycloalkyl, C3-C22-alkenyl, C1-C12-alkoxy, C1-C12-alkylsulfanyl, hydroxy-C1-C8-alkyl, halogen, NR″1R″2, NO2, CN, phenyl, phenyloxy or R1 and R2 or R2 and R3 or R3 and R4 or R6 and R7 or R7 and R8 or R8 and R9 are linked together to form a five- or 6-membered alicylic, aromatic or heterocyclic ring together with their 2 corresponding carbons atoms, to which they are attached.