Five curvularin macrolides (1-5) were isolated from the cultured broth of marine actinomycete Pseudonocardia sp. HS7 that was obtained from the cloacal aperture of sea cucumber Holothuria moebii. The structures of these isolates were characterized as (11S,15R)-11-hydroxycurvularin (1), (11R,15R)-11-hydroxycurvularin (2), curvularin-7-O-α-D-glucopyranoside (3), trans-dehydrocurvularin (4) and curvularin (5) based on their NMR and HRESIMS data as well as chemical degradation. Compound 3 is a new macrolide with a rare α-D-glucopyranose substituent. Compounds 1-4, 5a and 5c (the acyl products of 5), suppressed the proliferation of all six tested cancer cell lines and 4 is the most active compound with IC50 values ranging from 0.59 to 3.39 μM. The 11-hydroxycurvularins 1 and 2 also showed antibacterial activity inhibiting the growth of Escherichia coli.
Keywords: Pseudonocardia sp. HS7; antibacterial activity; curvularin glycoside; cytotoxic.