Altenusin derivatives from mangrove endophytic fungus Alternaria sp. SK6YW3L

摘要

Five new altenusin derivatives, compounds 1–5 , along with six known analogues 6–11 , were isolated from a culture of the endophytic fungus Alternaria sp. SK6YW3L, which was isolated from a fresh fruit of the mangrove plant Sonneratia caseolaris , collected from the South China Sea. Their structures were elucidated by analysis of 1D and 2D NMR and high resolution mass spectroscopic data. The absolute configurations of compounds 1–3 and 5 were assigned by quantum chemical calculations of the electronic circular dichroic (ECD) spectra. Structures of compounds 1 and 4 were further confirmed by single-crystal X-ray diffraction experiments using Cu Kα radiation. All isolated compounds were evaluated for α-glucosidase inhibitory activity, and compounds 2 , 3 and 9 exhibited moderate inhibitory activity. The plausible biosynthetic pathways for all the compounds were proposed.