Phytochemical and Cytotoxicity Studies of Callistemon viminalis Leaves Extract Growing in Egypt

Objective: To isolate and identify new compounds from the methanolic extract of Callistemon viminalis leaves collected in Cairo, Egypt and evaluate its cytotoxic and hepatoprotective potentials. Methods: The methanolic extract of Callistemon viminalis leaves was fractionated and subjected to different chromatographic techniques to isolate pure, new compounds which were identified by nuclear magnetic resonance (NMR), spectroscopic analysis and mass spectrometric methods. The methanolic extract of the leaves was assessed for its cytotoxic and hepatoprotective activities against Hepatocellular carcinoma cells (Hep G-2 cell line) by estimating the viability of the HepG2 cells by the MTT reduction assay. Results: Six compounds were isolated and identified for the first time from the methanolic extract of Callistemon viminalis leaves, three compounds are new flavonoids namely; 3-O-[α-L-arabinopyranosyl- (1→2)-α-L-arabinopyranosyl)]-3′-O-methylquercetin (C1); 5,7,3',4' tetrahydroxy isoflavone-7-O-α- L-1C4- rhamnopyranosyl (1'''-6'')-O-β-D-4C1-glucopyranoside (C2) and 6-methyl-5,7-dihydroxy-4'- methoxyflavone (C6) along with the three known ones; hyperoside (C3), rutin (C4) and isoquercitrin (C5). Conclusion: The methanolic extract of the leaves showed strong cytotoxic activity against Hepatocellular carcinoma cells (Hep G-2 cell line) and weak hepatoprotective effect.