Stabilizer, organic material composition, and method for stabilizing organic material

A stabilizer comprising:

• (A) a compound selected from the group consisting of a compound represented by formula (1):
• wherein
• R1, R2, R4 and R5 each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, an alkylcycloalkyl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms or a phenyl group,
• R3 each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms,
• X represents a single bond, a sulfur atom or a group —CH(—R13)—, wherein R13 represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms,
• A represents an alkylene group having 1 to 8 carbon atoms or a group *—C(═O)—R14—, wherein R14 represents a single bond or an alkylene group having 1 to 8 carbon atoms, and * represents a bond to oxygen,
• any one of Y and Z represents a hydroxyl group, an alkoxy group having 1 to 8 carbon atoms or an aralkyloxy group having 7 to 12 carbon atoms, and the other thereof represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms,
• and a compound represented by formula (2):
• wherein
• R6 and R8 each independently represent a hydrogen atom, a methyl group, or an alkyl group having 5 to 8 carbon atoms,
• R7 each independently represents a hydrogen atom or a hydroxyl group,
• R9 each independently represents a hydrogen atom or a group —C15H25-31, provided that at least one R6, R7, R8 or R9 is not a hydrogen atom, and
• (B) a compound represented by formula (3):
• wherein R10, R11 and R12 each independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an arylalkyl group having 7 to 20 carbon atoms in total, provided that at least one of R10, R11 and R12 is not a hydrogen atom, wherein
• a content of the compound (B) is 0.01 to 50 parts by mass per 100 parts by mass of the compound (A).