New bioactive pyridone alkaloids and pyranones from endophytic fungus Phomopsis tersa SC5100.

Three previously unreported pyridone alkaloids (1-3), three undescribed pyranones (4-6), along with six known congeners (7-12), were obtained from the solid culture of endophytic fungus Phomopsis tersa SC5100. Their structures, incorporating absolute configurations, were elucidated based on comprehensive analyses of 1D and 2D NMR data, HRESIMS spectrometry, single-crystal X-ray diffraction analysis (CuKα), and electronic circular dichroism (ECD) calculations. Compounds 1-3 exhibited outstanding immunosuppressive activities on concanavalin A-induced T cell proliferation with IC50 values of 10.5, 13.7, and 15.7 μM and on lipopolysaccharide-induced B cell proliferation with IC50 values of 12.8, 14.1, and 16.8 μM, respectively, and flow cytometry assays further revealed that 1 potently inhibited T cell proliferation via induction of apoptosis in a dose-dependent manner. Moreover, compounds 4-6 and 9-12 exhibited moderate to excellent inhibitory activity against α-glycosidase, with IC50 values ranging from 36.4 to 207.4 μM.