Antioxidant and use thereof

A compound represented by the following formula (1) or a salt thereof:

• where in the formula (1),
• an A ring and a B ring may be the same or different and represented by the following formula (2) or (3):
• where in the formula (2),
• R1 is a halogen atom, an alkyl group, an amino group, a cyano group, a hydroxy group, a sulfo group, a carboxyl group, an alkoxy group, a hydroxyalkyl group, an acyl group, an alkenyl group, an alkynyl group, or an aryl group that may have a substituent,
• R2 is a halogen atom, an alkyl group, an amino group, a cyano group, a hydroxy group, a sulfo group, a carboxyl group, an alkoxy group, a hydroxyalkyl group, an acyl group, or an alkynyl group that may have a substituent, and
• R3 is a halogen atom, an amino group, a cyano group, a hydroxy group, a sulfo group, a carboxyl group, an alkoxy group, a hydroxyalkyl group, an acyl group, an alkynyl group, or an aryl group that may have a substituent, and
• where in the formula (3),
• R4 is a halogen atom, an alkyl group, an amino group, a cyano group, a hydroxy group, a sulfo group, a carboxyl group, an alkoxy group, a hydroxyalkyl group, an acyl group, an alkenyl group, an alkynyl group, or an aryl group that may have a substituent,
• R5 is a halogen atom, an alkyl group, an amino group, a cyano group, a hydroxy group, a sulfo group, a carboxyl group, an alkoxy group, a hydroxyalkyl group, an acyl group, an alkenyl group, an alkynyl group, or an aryl group that may have a substituent, and
• R6 is an oxygen atom, a halogen atom, an alkyl group, an amino group, a cyano group, a hydroxy group, a sulfo group, a carboxyl group, an alkoxy group, a hydroxyalkyl group, an acyl group, an alkenyl group, an alkynyl group, or an aryl group that may have a substituent, and
• L is a saturated hydrocarbon group having 2 to 6 carbon atoms.