Cytotoxic constituents of Oldenlandia umbellata and isolation of a new symmetrical coumarin dimer

Abstract

The study was aimed at exploring cytotoxic activity of Oldenlandia umbellata and its chemical constituents. Cell viability assay of crude methanolic extract of aerial parts of O. umbellata (HUM), its ether soluble fraction (HUM-E) and butanol soluble fraction (HUM-B) against colon cancer HT-29, lung epithelial A549 and breast adenocarcinoma MDA-MB-231 cell lines showed HUM-E to be significantly cytotoxic with IC50 values of 25.7, 67.7 and 69.3 μg/mL, against HT-29, A549 and MDA-MB-231, respectively. Chemical investigation of HUM-E and HUM-B resulted in the isolation of a novel symmetrical coumarin dimer named oledicoumarin (1), together with eleven known compounds, hedyotiscone B (2), cedrelopsin (3), pheophorbide A methyl ester (4), deacetyl asperuloside (5), scandoside methyl ester (6), asperulosidic acid (7), scandoside (8), nicotinic acid (9), 6α-hydroxy geniposide (10) anthragallol 1,2-dimethyl ether (11) and anthragallol 1,3-dimethyl ether (12). All compounds were isolated for the first time from O. umbellata except anthragallols. This is the foremost report exploring the presence of coumarin derivatives in O. umbellata. Testing of cytotoxicity of isolated constituents revealed that compounds 3, 4, 11 and 12 showed significant inhibition against A549 cells with IC50 values of 3.6–5.9 μg/mL. Compounds 4, 11 and 12 showed marked inhibitory effect against MDA-MB-231 cells (IC50 3.6–9.1 μg/mL). Compounds 4 (IC50 1.7 μg/mL) and 7 (IC50 6.1 μg/mL) were highly active against HT-29 cells. In summary, the less polar fraction of O. umbellata and its constituents were found to be cytotoxic.