Isolation and evaluation of phytoconstituents from red alga Acanthophora spicifera as potential apoptotic agents towards A549 and HeLa cancer cells lines

In the present work, we isolated, characterized and examined the anticancer effect of bioactive molecules from Acanthophora spicifera (red algae) on A549 and HeLa cancer cell lines and compared with normal HEK cells. Among the different solvent fractions subjected to chromatographic purification, three molecules isolated showed potential cytotoxicity and induced apoptosis in a dose dependent manner. The structure of the active components was identified as Cholest-4-ene-3,6-dione, (1) a steroid and two non-steroid molecules namely 2-bromohexandecanoic acid (2) and 6-bromo indole (3) by GC–MS, FTIR and NMR (1H &13C) analysis. Compound 1 exhibited better cytotoxicity with an IC50 of 10.01 ± 0.11 μM (A549) and 12.32 ± 0.08 μM (HeLa) (1) than that of compound (2) IC50 of 72.6 ± 0.10 μM (A549), 26.42 ± 0.11 μM (HeLa) and (3) 108.2 ± 0.15 μM (A549) and 71.68 ± 0.60 μM (HeLa) at 24 h. Mechanistic investigation on apoptosis by the selected compounds was further confirmed by dual AO/EB and Annexin-V/PI staining assay. Interestingly, compound 1 also displayed remarkable loss of mitochondrial membrane potential (MMP assay), increased level of reactive oxygen species (ROS assay) and cell cycle arrest at sub-G1 phase. Further, Western blot analysis confirmed the involvement of caspase signaling cascade in A549 cell death by compound 1. Our findings demonstrate that the red alga Acanthophora spicifera from Gulf of Mannar is a potent source of these bioactive leads with an efficient anticancer activity mediated by apoptosis and autophagy.