Macrolide sesquiterpene pyridine alkaloids from the stems of Tripterygium regelii.

Nine new monomacrolide sesquiterpene pyridine alkaloids, macroregelines A-I (1-9), were isolated from the stems of Tripterygium regelii, along with a known alkaloid, tripfordine B. The structures of all the isolated compounds were characterized by extensive one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopic analyses, as well as high-resolution electrospray-ionization mass spectrometry (HRESIMS) data. Compounds 4, 5, 6, and 8 showed antiproliferative effect on human rheumatoid arthritis synovial cell line MH7A at concentration of 20 μM, reducing their viability by 7.5, 18.0, 9.0, and 18.2 %, respectively.