Two new indole alkaloids from Tabernaemontana contorta Stapf.

Graphical abstract Highlights • Plants of the genus Tabernaemontana mainly contain monoterpenoid indole alkaloids as well as triterpenoids. • This article reports the isolation of two new monoterpenoid indole alkaloids. • The compounds were isolated using usual chromatographic method and their structures elucidated using 1D and 2D NMR. Abstract Two new indole alkaloid derivatives, 5,6-dioxo-11-methoxy voacangine (1) and (-)-apparicin-21-one (2), together with four known compounds, voacangine (3), ursolic acid (4), 3-methoxyursolic acid (5) and asiatic acid (6) were isolated from the fruits of Tabernaemontana contorta Stapf (Apocynaceae). Their structures were determined using 1D and 2D NMR and HRESI-MS measurements. The new indole alkaloids were tested on lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells to determine their inhibitory effect on nitric oxide (NO) production, but did not have any significant inhibitory activity. Compound (1) slightly increased the proliferation of RAW 264.7 cells in relation with the increased level of NO released by these cells. [ABSTRACT FROM AUTHOR]