Gilvocarcin M is the minor analogue of a complex of C-glycoside antitumor actives isolated from a Streptomyces sp. Gilvocarcin M contains a methyl group in the 8-position, and is less active than the vinyl analogue (gilvocarcin V), which is thought to act as an inhibitor of human topoisomerase II. Gilvocarcin M displays potent antibacterial, antifungal, antiviral and antitumor activity. Recent research suggests that the gilvocarcins act as photoactivated cross-linkers of DNA to histones.