Anti-parasitic compounds from Streptomyces sp. strains isolated from Mediterranean sponges

Abstract

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 IC(50) < 0.11 microM; staurosporine IC(50) 5.30 microM) and Trypanosoma brucei brucei (valinomycin IC(50) 0.0032 microM; staurosporine IC(50) 0.022 microM; butenolide IC(50) 31.77 microM). 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.

Keywords: Streptomyces; anti-parasitic; butenolide; marine sponges; staurosporine; valinomycin.

Figure 1

Neighbor-joining tree of the strains and representative species of the genus Streptomyces based on nearly complete 16S rRNA gene sequences. Numbers at the nodes indicate the levels of bootstrap support based on 1000 resampled data sets. Only values greater than 50% are shown. The arrow points to the outgroup consisting of six species belonging to Enterobacteriaceae and Pasteurellaceae. The scale bar indicates 0.01 substitution per nucleotide position.

Figure 2

Compounds isolated from Streptomyces sp. strains.