Thiolactones and Δ 8,9 -Pregnene Steroids from the Marine-Derived Fungus Meira sp. 1210CH-42 and Their α -Glucosidase Inhibitory Activity.

The fungal genus Meira was first reported in 2003 and has mostly been found on land. This is the first report of second metabolites from the marine-derived yeast-like fungus Meira sp. One new thiolactone ( 1 ), along with one revised thiolactone ( 2 ), two new Δ 8,9 -steroids ( 4 , 5 ), and one known Δ 8,9 -steroid ( 3 ), were isolated from the Meira sp. 1210CH-42. Their structures were elucidated based on the comprehensive spectroscopic data analysis of 1D, 2D NMR, HR-ESIMS, ECD calculations, and the pyridine-induced deshielding effect. The structure of 5 was confirmed by oxidation of 4 to semisynthetic 5 . In the α -glucosidase inhibition assay, compounds 2 - 4 showed potent in vitro inhibitory activity with IC 50 values of 148.4, 279.7, and 86.0 μM, respectively. Compounds 2 - 4 exhibited superior activity as compared to acarbose (IC 50 = 418.9 μM).