A novel compound derived from the culture product of an actinomycete and having an antitumor activity is provided. Provided is a compound represented by any one of formulas (I), (II) and (III)or an optical isomer thereof or a pharmaceutically acceptable salt thereof which can be isolated from the culture fluid of an actinomycete which belongs to the genus Streptomyces, wherein R1, R2, R5 and R6 each independently represent a hydrogen atom, a methyl group, a hydroxymethyl group, a hydroxyl group, or a double bond by which R1 and R2 or R5 and R6 are bonded； R3, R4, R7 and R8 each independently represent a methyl group or a hydroxymethyl group； and R9 represents a hydrogen atom or a hydroxyl group.
