Alternariasin A, new pentacyclic cytochalasin from the fungus Alternaria alternate.

Alternariasin A (1), one new cytochalasin possessing the benzo[4,5]indeno[2,1-d]isoindole-1,3,13(2H,3aH)-trione skeleton, and five known compounds 2-6 were isolated from the solid cultures of the Midui Glacier-derived fungus Alternaria alternata. Their structures were elucidated by NMR and MS spectroscopic analyses and by a comparison with data from the literature. The absolute configuration of 1 was assigned by combination of experimental and calculated electronic circular dichroism (ECD) spectra. Compound 1 displayed antibacterial activity against the S. aureus, B. subtilis and E. coli with MIC values of 16.7, 16.7 and 33.3 μΜ, respectively. While compound 3 showed potent cytotoxicity against a small panel of human tumour cell lines.