Studies on the isotetracenone antibiotics. IV. Hatomarubigins A, B, C and D, new isotetracenone antibiotics effective against multidrug-resistant tumor cells.

A complex of new isotetracenone group antibiotics was isolated from the cultured broth of Streptomyces sp. 2238-SVT4. It consisted of four related compounds, designated hatomarubigins A, B, C and D, whose structures were elucidated by NMR spectral analysis including a variety of 2D techniques. They enhanced the cytotoxicity of colchicine against multidrug-resistant tumor cells.