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 R 1 R 2 , R 5 and R 6 each independently represent a hydrogen atom, a methyl group, a hydroxymethyl group, a hydroxyl group, or a double bond by which R 1 and R 2 or R 5 and R 6 are bonded； R 3 , R 4 , R 7 and R 8 each independently represent a methyl group or a hydroxymethyl group； and R 9 represents a hydrogen atom or a hydroxyl group.
