Thiolactones and Δ[sup.8,9]-Pregnene Steroids from the Marine-Derived Fungus IMeira/I sp. 1210CH-42 and Their Iα/I-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[sup.8,9] -steroids (4, 5), and one known Δ[sup.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[sub.50] values of 148.4, 279.7, and 86.0 μM, respectively. Compounds 2–4 exhibited superior activity as compared to acarbose (IC[sub.50] = 418.9 μM).