Hydroquinone derivatives from the marine-derived fungus Gliomastix sp.

Eight new hydroquinone derivatives, gliomastins A-D (1-4), 9-O-methylgliomastin C (5), acremonin A 1-O-beta-D-glucopyranoside (6), gliomastin E 1-O-beta-D-glucopyranoside (7), and 6'-O-acetyl-isohomoarbutin (8), together with seven known analogues were isolated from the marine-derived fungus Gliomastix sp. Their structures were elucidated by extensive spectroscopic analysis including 1D and 2D NMR measurements aided by DFT NMR calculations as well as MS data. TDDFT-ECD and OR calculations were performed to determine the absolute configurations of 1 and the aglycones of 6 and 7. Compound 1 features a novel skeleton, biogenetically derived from a Diels-Alder reaction between derivatives of 11 and 13. Compound 2 represents a rare sulfur-containing alkaloid derived from the known hydroquinone 13. Compounds 1, 10 and 12 showed strong cytotoxicity against the L5178 Upsilon mouse lymphoma cell line with IC50 values of 1.8, 1.0 and 1.1 mu M, respectively. Compound 3 exhibited moderate antitubercular activity against Mycobacterium tuberculosis with a MIC value of 12.5 mu M.