Abstract: A compound represented by the general formula (I) or a salt thereof: wherein represents —CH?CH—, —CH2—CH2— or the like, between R1 and the carbon atom at 4?-position represents a single bond or a double bond, between R2 and the carbon atom at 5-position represents a single bond or a double bond, and for example, 1) when represents —CH?CH— or —CH2—CH2—, and between R1 and the carbon atom at 4?-position represents a double bond, R1 represents ?C(R11)(R12) (wherein R13 represents a lower alkyl group or the like and R12 represents a hydrogen atom or the like) or the like, and R2 represents a hydroxyl group or the like, or R2 may be combined together with the carbon atom at 5-position to form a carbonyl group, and 2) when represents —CH?CH— or —CH2—CH2—, and between R1 and the carbon atom at 4?-position represents a single bond, R1 represents —OCH(R1a)(R1b) (wherein R1a represents a lower alkyl or the like and R1b represents a hydrogen atom or the like) or the like, and R2 represen