Tricin 4′-O-(erythro-β-guaiacylglyceryl) ether and tricin 4′-O-(threo-β-guaiacylglyceryl) ether isolated from Njavara (Oryza sativa L. var. Njavara), induce apoptosis in multiple tumor cells by mitochondrial pathway

Njavara is an important medicinal rice variety of Kerala, India widely used in Ayurveda for the treatment of rheumatoid arthritis, paralysis, neurodegenerative diseases and in rejuvenation therapy. The study evaluated, for the first time, antitumor effects of the two rare flavonolignans, tricin 4′-O-(erythro-β-guaiacylglyceryl) ether (compound 1) and tricin 4′-O-(threo-β-guaiacylglyceryl) ether (compound 2), isolated from ‘Njavara’ black. Both the compounds induced apoptosis in three cancer cell lines colon adenocarcinoma cell line HCT 116, ovarian cancer cell line SKOV3 and breast cancer cell line MCF-7. Chromatin condensation in the three cancer cell lines by Hoechst staining showed >50 % of apoptosis by compounds 1 and 2 at concentration 40 and 30 μg/ml, respectively after 48 h. Further studies substantiated that both the compounds targeted cancer cells through mitochondrial membrane potential loss and subsequent chromatin condensation. Both compounds significantly increased the Annexin V binding thus confirming compounds 1 and 2 to be potential apoptotic agents.