Crepidatumines C and D, Two New Indolizidine Alkaloids from Lindl. ex Paxt.

Two new indolizidine alkaloids, crepidatumines C () and D (), together with crepidine (), isocrepidamine (), and crepidamine () were isolated from the Lindl. ex Paxt. X-ray diffraction experiments established the absolute configurations of known compounds and . The planar structures and relative configurations of new compounds and were elucidated by extensive spectra analysis including HR-ESI-MS, NMR (H, C, H-H COSY, HSQC, HMBC, and NOESY spectra), and the absolute configurations of and were suggested on the basis of possible biosynthetic pathways. The biological results confirmed that isocrepidamine () displayed a potent hypoglycemic effect in vitro without cytotoxicity.