Chicamycin B

Structures of chicamycins A and B have been determined from a series of chemical degradation studies coupled with spectroscopic analysis. Chicamycin A is 2(S),11(R), 11a (S)-1,2,3,10, 11, 11a -hexahydro-2,8-dihydroxy-7,11-dimethoxy-5H-pyrrolo-[2,1-c] [1,4]-benzodiazepin-5-one, and chicamycin B is 2(S), 11a (S)-1,2,3, 11a -tetrahydro-2,8-dihydroxy-7 -methoxy-5H-pyrrolo-[2,1-c][1,4]-benzodiazepin-5-one which is the demethanol form of chicamycin A. The structure of chicamycin B is closely related to that of neothramycin , differing only in the position of a hydroxyl substituent on the pyrrolidine ring.

The diversity of actinomycetes associated with the marine sponge Coscinoderma mathewsi collected from Hurghada (Egypt) was studied. Twenty-three actinomycetes were separated and identified based on the 16S rDNA gene sequence analysis. Out of them, three isolates were classified as novel species of the genera Micromonospora, Nocardia, and Gordonia. Genome sequencing of actinomycete strains has revealed many silent biosynthetic gene clusters and has shown their exceptional capacity for the production of secondary metabolites, not observed under classical cultivation conditions. Therefore, the effect of mycolic-acid-containing bacteria or mycolic acid on the biosynthesis of cryptic natural products was investigated. Sponge-derived actinomycete Micromonospora sp. UA17 was co-cultured using liquid fermentation with two mycolic acid-containing actinomycetes (Gordonia sp. UA19 and Nocardia sp. UA 23), or supplemented with pure mycolic acid. LC-HRESIMS data were analyzed to compare natural production across all crude extracts. Micromonospora sp. UA17 was rich with isotetracenone, indolocarbazole, and anthracycline analogs. Some co-culture extracts showed metabolites such as a chlorocardicin, neocopiamycin A, and chicamycin B that were not found in the respective monocultures, suggesting a mycolic acid effect on the induction of cryptic natural product biosynthetic pathways. The antibacterial, antifungal, and antiparasitic activities for the different cultures extracts were also tested.

Chicamycin is a new antitumor antibiotic produced by a strain of Streptomyces albus, No. J576 -99. The antibiotic is extractable into organic solvents from the fermentation broth and is obtained in two active forms, chicamycins A and B, depending upon the isolation procedure used. Chicamycin A is not a natural antibiotic but the methanol adduct of naturally produced chicamycin B. Both forms of the antibiotic have weak antibacterial activity against some Gram-positive and acid-fast bacteria. They inhibit the growth of experimental tumors such as P388 mouse leukemia.