Alkaloids and Iridoids From <i>Phlogacanthus curviflorus</i>

Four unreported pyridine alkaloids, curviflorines A-D (1-4), two undescribed iridoids, curviridoids A and B (5 and 6), and one known iridoid glycoside (7), were isolated from the twigs and leaves of Phlogacanthus curviflorus. The structures of these compounds were established by detailed interpretation of MS and NMR data, with the absolute configurations being assigned via comparison of experimental and calculated electronic circular dichroism spectra. Notably, it is the first report of alkaloidal constituents (1-4) from the genus Phlogacanthus. Compounds 1-7 did not show obvious inhibitory activities against α-glucosidase and NO production (in RAW264.7 macrophages), nor did they exhibit anti-oxidant activity and cytotoxicity towards MDA-MB231, A549 and HeLa cancer cell lines. Nevertheless, alkaloids 1-4 did exert a significant suppressing effect on TGF-β1-induced upregulation of the fibrotic marker protein fibronectin in HK-2 cells, indicating their antifibrotic potential.