Peganumine B-I and two enantiomers: new alkaloids from the seeds of Peganum harmala Linn. and their potential cytotoxicity and cholinesterase inhibitory activities

Ten new alkaloids (peganumine B-I and two enantiomers), containing five β-carbolines, three quinazolones, two compounds with both of the above skeletons, and one amphoteric alkaloid with a four-membered ring, were isolated from the ethanol extract of Peganum harmala. Their structures were elucidated on the basis of spectral data using 1D and 2D NMR, X-ray crystallographic analysis, CD, and ECD. Peganumine B showed potential inhibitory activity against both AChE and BChE with IC50 values of 0.25 ± 0.04, and 1.45 ± 0.34 μM, respectively. Peganumine C, peganumine D, and peganumine I were found to have selective inhibitory activity against AChE with IC50 values of 14.38 ± 2.49, 5.71 ± 1.22, and 7.17 ± 1.45 μM, respectively. Peganumine G and peganumine H showed significant cytotoxicity against a ZR-75-1 cell line with IC50 values of 6.20 ± 2.71, and 2.43 ± 0.79 μM, respectively.