Pharmacological evaluation of phytochemicals from South Indian Black Turmeric (Curcuma caesia Roxb.) to target cancer apoptosis

Curcuma caesia Roxb. (Black turmeric), a perennial herb of the family Zingiberaceae is indigenous to India. C. caesia is used as a spice, food preservative and coloring agent commonly in the Indian subcontinent. Functional parametric pharmacological evaluations like drug ability and toxicity profile of this endangered species is poorly documented. In our present study, among all the extracts of dried C. caesia rhizome viz- hexane, ethyl acetate, methanol and water tested for free radical scavenging capacity by total antioxidant activity (TAO) method, Hexane Rhizome Extract (HRE) was found to possess remarkable activity (1200 mg ascorbic acid equivalent/100 g). In MTT assay across three cancer cell lines and a control cell line, HRE exhibited a dose-dependent inhibition only in cancer cells, with notable activity in HepG2 cell lines (IC50: 0976 µg/mL). Further, western blotting and flow cytometry experiments proved that HRE induces cell arrest at G2/M phase along with cellular apoptosis as suggestive by multiple-point mitochondrial mediated intrinsic pathway of Programmed Cell Death (PCD). Gas Chromatography-Mass Spectrophotometry (GC-MS) analysis of HRE suggested twenty compounds that when docked in silico with Tubulin (1SA0) and Epidermal Growth Factor Receptor/ EGFR (1XKK) showed very intimate binding with the original ligands. Our results provided significant evidence of the toxicity mechanisms of HRE that may be beneficial for more rational applications of drug discovery for slowing down cancer progression.