SF 2446A2

New antibiotics SF2446A1, A2, A3, B1 and B2 have been isolated from the culture of Streptomyces sp. SF2446 and antibiotic SF2446B3 has been obtained by methanolysis of SF2446B1 or B2. SF2446A1, A2 and B1 showed strong inhibitory activities against mycoplasmas and Gram-positive bacteria. Empirical molecular formulae of antibiotics SF2446-A1, A2, A3, B1, B2 and B3 were determined to be C34H35NO15, C26H21NO11, C34H35NO14, C34H35NO14 and C26H21NO10, respectively.

Structures of new antibiotics SF2446A1, A2, A3, B1, B2 and B3 have been deduced by means of spectral analyses and chemical studies. The structure of SF2446A1 which is a main product of fermentation and has the strongest antimicrobial activity, has been proposed to be 11-(2,4-di-O-methyl-beta-L-rhamnopyranosyl)amino-5,6,6a,14a-tetrah ydro- 1,6,8,14a-tetrahydroxy-6a-methoxy-2-methoxycarbonyl-3-methyl- benzo[a]naphthacene-7,9,12,14-tetra-one. All of antibiotics have a novel benzo[a]naphthacene quinone skeleton and SF2446A1, A2, B1 and B2 have an N-glycosidic linkage with 2,4-di-O-methyl-L-rhamnose.

Infectious diseases caused by chlamydia or schistosomes are a major health problem worldwide, and particularly so in developing countries. The lack of appropriate vaccines renders the search for potent natural products against these disease-causing agents an urgent endeavor. Sponge-associated actinomycetes represent a rich reservoir for natural products. Among them, members of the genus Streptomyces are capable of synthesizing an impressive array of diverse natural products with a wide variety of biological activities. The naphthacene glycoside SF2446A2 was isolated from the calcium alginate beads culture of Streptomyces sp. strain RV15 that had originally been obtained from the Mediterranean sponge Dysidea tupha. Its structure was identified by spectroscopic analysis and MS and comparison with the literature data. SF2446A2 showed inhibitory activity against Chlamydia trachomatis and was able to inhibit the primary infection in a dose-dependent manner, as well as progeny formation. Moreover, it caused disruptive effects on the surface area of Schistosoma mansoni and affected the gonads by impairing oogenesis and spermatogenesis. Our current study demonstrates that sponge-associated actinomycetes are capable of providing compounds with new pharmacological activities and with relevance to drug discovery.