Secondary metabolites by chemical screening. Part 19. SM 196 A and B, novel biologically active angucyclinones from Streptomyces sp.

Application of a method of chemical screening2*, which based on the prior work of Zahner et al.3\ gave rise to the detection, isolation and structure elucidation of two new angucyclinones4) exhibiting biological activity. In addition, the known compounds 6-deoxy-8-0-methylrabelomycin (3)5'6) and X-14881 E (4)7) were detected in the same culture broth. The producing organism Streptomyces sp. (DSM 4769) was isolated from a soil sample collected near Ajanta (India) and exhibits tightly spiraled, red spores with a smooth surface. Melanin production is positive. Cultivation wascarried out in a seed medium (meat flour 2%, malt extract 10%, CaCO3 1%, pH adjusted to 7.2 prior to sterilization) inoculated from an agar slant culture and incubated for 48 hours at 27°C. The resulted seed medium (5%) was used to inoculate the production medium(glycerol 3%, casein peptone 0.2%, K2HPO4 0.1%, NaCl 0.1%, MgSO4-7H2O 0.05% and 5ml of a mineral solution containing CaCl2-2H2O 3g, FeC6H5O7 lg, MnSO4 0.2g, ZnCl2 0.1g5