Quinoline, Indole, and Isogranatanine Alkaloids from Malayan .

Nine new alkaloids, eugeniinalines A-H (-) and (+)-eburnamenine -oxide (), comprising one quinoline, six indole, and two isogranatanine alkaloids, were isolated from the stem-bark extract of the Malayan . The structures and absolute configurations of these alkaloids were established based on the analysis of the spectroscopic data, GIAO NMR calculations, DP4+ probability analysis, TDDFT-ECD method, and X-ray diffraction analysis. Eugeniinaline A () represents a new pentacyclic quinoline alkaloid with a 6/6/5/6/7 ring system. Eugeniinaline G () and its -derivative, eugeniinaline H (), were the first isogranatanine alkaloids isolated as natural products. The known alkaloids leucolusine () and melokhanine A () were found to be the same compound, based on comparison of the spectroscopic data of both compounds, with the absolute configuration of (7, 20, 21). Eugeniinalines A and G ( and ) showed cytotoxic activity against the HT-29 cancer cell line with IC values of 7.1 and 7.2 μM, respectively.