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 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.
Highlights
The class Actinobacteria, bacteria belonging to the order Actinomycetales, are common soil inhabitants that have the unprecedented ability to produce a wide range of secondary metabolites
May 2006 were cultivated as described previously [15,16,18]. 16S rRNA gene sequencing revealed the affiliation of four strains, namely isolate 11 (GU214750), isolate 34 (GU214751), isolate 22 (GU214752) and isolate TO3 (GU214749) to the genus Streptomyces (Figure 1)
99.7–99.9% sequence similarities to validly described species of the genus Streptomyces
Summary
The class Actinobacteria, bacteria belonging to the order Actinomycetales, are common soil inhabitants that have the unprecedented ability to produce a wide range of secondary metabolites.Among the more than 140 described actinomycete genera, only a few are responsible for the majority of over 20,000 microbial natural products identified so far. 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. These compounds exhibited novel anti-parasitic activities against Leishmania major (valinomycin IC50 < 0.11 μM; staurosporine IC50 5.30 μM) and Trypanosoma brucei brucei
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