| Summary: | Actinomycetes are prolific producers of pharmacologically important compounds accounting for about 70% of the naturally derived antibiotics that are currently in clinical use. In this study, we report on the isolation of Streptomyces sp. strains from Mediterranean sponges, on their secondary metabolite production and on their screening for anti-infective activities. Bioassay-guided isolation and purification yielded three previously known compounds namely, cyclic depsipeptide valinomycin, indolocarbazole alkaloid staurosporine and butenolide. This is the first report of the isolation of valinomycin from a marine source. These compounds exhibited novel anti-parasitic activities specifically against Leishmania major (valinomycin IC50 < 0.11 µM; staurosporine IC50 5.30 µM) and Trypanosoma brucei brucei (valinomycin IC50 0.0032 µM; staurosporine IC50 0.022 µM; butenolide IC50 31.77 µM). These results underscore the potential of marine actinomycetes to produce bioactive compounds as well as the re-evaluation of previously known compounds for novel anti-infective activities.
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