Bafilomycin M, a new cytotoxic bafilomycin produced by a Streptomyces sp. isolated from a marine sponge Theonella sp

A new 16-membered diene macrolide, bafilomycin M ( 1 ), was produced from a Streptomyces sp. GIC10-1, which was originally isolated from a marine sponge Theonella sp. The structure of 1 was established by spectroscopic methods and this compound was found to exhibit cytotoxicity toward K-562, HL-60, SUPT-1, and LNCaP tumor cells with IC 50 values 0.060, 0.011, 0.047, and 0.389 μg/mL, respectively.