Two new alkaloids, taberdines L (1) and M (2), together with six known alkaloids, were isolated from the twigs and leaves of Tabernaemontana divaricata. Taberdine L (1) represents the first optically active natural member of the allo iboga class of alkaloids with the ethyl side chain in a bridgehead position. Their structures including absolute configuration were elucidated by a combination of MS, NMR, and ECD calculation.The in vitro cytotoxic activities of 1 and 2 against five human cancer cell lines were also evaluated.
Uncarialines A-E (1–5), five undescribed monoterpene indole alkaloids, together with five known analogues were obtained from the stems of Uncaria rhynchophylla. Alkaloids 1–3 were unique 3,4-seco-tricyclic alkaloids with a 6/5/10 ring system, while 4 and 5 possessed a rare rearranged scaffold originated from corynantheine-type alkaloids with C-2/C-7 oxidation. Their structures were characterized by a comprehensive analysis of MS, NMR, and ECD. Their effects on blood clotting times of human plasma were evaluated and alkaloid 5 had a slight prolongation effect on both thrombin time and activated partial thromboplastin time (p < 0.001).
Graphical Abstract
Two new monoterpenoid indole alkaloids, (2R, 7R, 16R, 20R, 21S)-12hydroxypleiocarpine (1) and (2S, 7R, 16S, 20R, 21S)-N-methoxycarbonyl-11,12methylenedioxy- 14,15 -kopsinaline (2), along with six known alkaloids were isolated from the methanol extract of the kernels of Kopsia arborea. Their structures including the absolute configurations were elucidated by HRESIMS, NMR spectroscopy, and quantum computational methods. Their cytotoxicity against two human cancer cell lines were also evaluated. Figure S2. 13 C NMR and DEPT spectra (125 MHz, chloroform-d) of 1 (↔) correlations of 1.
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