A new curvularin glycoside and its cytotoxic and antibacterial analogues from marine actinomycete Pseudonocardia sp. HS7

Abstract

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
• curvularin glycoside
• cytotoxic
• antibacterial activity

Acknowledgements

Authors also thank Mrs. Jianyang Pan at Pharmaceutical Informatics Institute of Zhejiang University for performing NMR spectrometry for structure elucidation.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by grants from the National Science Foundation of China [grant number 81273428] and the Cross-Disciplinary Research for Ocean Science of Zhejiang University [grant number 2012HY018B]. We greatly appreciate Drs. Zhongjun Ma and Pinmei Wang at Ocean College of Zhejiang University for donating samples of Staphylococcus aureus and Escherichia coli.