Kapurimycin A2

As a result of screening for antitumor agents from actinomycetes, the kepurimycins were isolated from Streptomyces sp. DO-115. The antibiotics were produced in a fermentation medium supplemented with high porous polymer resin which adsorbs antibiotics and results in an increase of titer. The active complex was isolated from the polymer resin by a solvent extraction procedure and was separated by column chromatography, into two minor and one major component, named A1, A2 and A3. The kepurimycins were active against bacteria, particularly Gram-positive organisms, and were cytotoxic to HeLa S3 human cerivical cancer cells and T24 human bladder carcinoma cells in vitro. Among the individual components of the kapurimycins, kapurimycin A3 exhibited the strongest antibacterial and cytotoxic activities. It showed a potent antitumor activity against murine leukemia P388 in vivo.

The kapurimycins A1, A2 and A3 were revealed to be new antitumor antibiotics with molecular formula of C27H26O9, C26H24O9 and C27H24O9, respectively. The structures of the kapurimycins were determined by NMR spectroscopic analysis. The kapurimycins are new class of polycyclic microbial metabolites having the tetrahydroanthra-gamma-pyrone skeleton and the beta, gamma-unsaturated delta-keto carboxylic acid structure. The individual components of the kapurimycins differ from one another in the side chain at the pyrone ring of the molecule.