A new flavonoid glycoside from Tapinanthus sp. (Loranthaceae) and evaluation of anticancer activity of extract and some isolated compounds.

The present work describes the isolation and anticancer activity of Tapinanthus sp. which is a hemi parasitic plant harvested on Combretum glutinosum, the host plant. Phytochemical study afforded a new flavonoid glycoside, tapinantoside (1) isolated for the first time from natural source, alongside six known compounds (2-7). Structure of compounds were elucidated by extensive spectroscopic analyses including 1 D and 2 D NMR, mass spectrometry and by comparison with literature data. The anticancer activity of extract and some isolated compounds were evaluated on glioblastoma (U87MG, C6) and prostate (PC-3) cancer cells. The methanol leaves extract showed good anticancer activity against U87 (IC50 = 21.40 µg/mL) and PC-3 cells (IC50 = 10.26 µg/mL). Compound 3 powerfully inhibits the proliferation of C6 (IC50 = 38.84 µM) and PC-3 cells (IC50 = 21.33 µM), while its effect was moderated on U87MG cells. Compound 1 and 7 were not active on all tested cancer cell lines.