Chen_2022_Phytochemistry_196_113089

Phytochemical investigation on the aerial parts of Tabernaemontana bufalina Lour. (Apocynaceae) led to the identification of four undescribed monoterpenoid indole alkaloids named taberbufamines A-D, an undescribed natural product, and fourteen known indole alkaloids. The structures of the undescribed alkaloids were established by spectroscopic and computational methods, and their absolute configurations were further determined by quantum chemical TDDFT calculations and the experimental ECD spectra. Taberbufamines A and B possessed an uncommon skeleton incorporating an indolizidino [8,7-b]indole motif with a 2-hydroxymethyl-butyl group attached at the pyrrolidine ring. Biosynthetically, Taberbufamines A and B might be derived from iboga-type alkaloid through rearrangement. Vobatensine C showed significant bioactivity against A-549, Bel-7402, and HCT-116 cells with IC(50) values of 2.61, 1.19, and 1.74 microM, respectively. Ervahanine A showed antimicrobial activity against Bacillus subtilis, Mycobacterium smegmatis, and Helicobacter pylori with MIC values of 4, 8, and 16 microg/mL, respectively. 19(S)-hydroxyibogamine was shown as butyrylcholinesterase inhibitor (IC(50) of 20.06 microM) and alpha-glycosidase inhibitor (IC(50) of 17.18 microM), while tabernamine, ervahanine B, and ervadivaricatine B only showed alpha-glycosidase inhibitory activities with IC(50) values in the range of 0.95-4.61 microM.