Bioassay-guided isolation of a new cytotoxic ceramide from Cyperus rotundus L.

Eight methanolic extracts were tested for their cytotoxic activity against HepG2, PC3, and MCF-7 cell lines using MTT assay. The rhizomes of Cyperus rotundus extract showed the highest activity, divided into five fractions (petroleum ether, methylene chloride, ethyl acetate, butanol, and aqueous) and re-evaluated for cytotoxicity. The petroleum ether fraction was the most active against the tested cell lines followed by the methylene chloride. The chromatographic investigation of petroleum ether and methylene chloride fractions resulted in identified of nine compounds; one new compound (1), along with eight known compounds; behenic acid (2), β-sitosterol (3), mandassidione (4), behenic acid monoglyceride (5), sitosteryl (6`-hentriacontanoyl)-β-D-galactopyranoside (6), β-sitosterol 3-O-β-D-glucoside (7), luteolin (8) and pinellic acid (9). Compound 1 was elucidated as a ceramide, 2`-[2-hydroxypentacosanoylamino]-1`, 3`, 4`-nonadecanetriol. The structure of 1 was confirmed by extensive analysis of both NMR (1D and 2D) data and HR-FAB-MS. The isolated compounds showed a very promising anticancer activity. Compounds 2–4 showed potent cytotoxic activity against the three tested cancer cell lines. Compounds 9 and 1 displayed inhibitory activity against HepG2 with IC50 values 6.81 to 8.075 µM, and PC3 with IC50 of 11.92 to 14.48 µM. While compounds 5 and 8 showed remarkable cytotoxic activity against the HepG2 with IC50 values of 7.641 to 10.02 µM. By analyzing the results of the MTT assay together with the obtained docking results we designed a proposed structure-activity relationship (SAR) to be a guide for further identification of new anticancer agents in the future.