Exploration of the aptitude to alleviate oxidative impairment and curb colorectal cancer manifestation by Nostoc calcicola in HT-29 adenocarcinoma cells

Abstract Background Marine cyanobacteria have been known to contain several unique bioactive compounds which have different therapeutic potentials. The current research focuses to identify the efficacy of Nostoc calcicola to counteract the harmful effects of free radicals and testing its anticancer activity against colorectal adenocarcinoma cells (HT-29). Results Methanol is used as a solvent for the extraction of bioactive metabolites from Nostoc calcicola followed by phytochemical screening representing the presence of flavonoids, phenols, tannins, saponins, and steroids to find out bioactive metabolites. Furthermore, evaluation of the extract efficacy revealed the profound ability of Nostoc calcicola to scavenge free radicals by neutralizing different reactive oxygen species. At 100 µg/mL concentration, it inhibited DPPH radicals (73.4%), enhanced phosphomolybdenum reduction (53.5%), displayed ferric-reducing power (55.1%), and finally the extract revealed remarkable hydroxyl radicals scavenging capacity (94.8%), compared to the standards. These compelling results emphasize the robust antioxidant potential of the Nostoc calcicola extract. In vitro, studies demonstrated the selective cytotoxic effects of methanol extracts of Nostoc calcicola on the HT-29 human colorectal cancer cell line, as indicated by IC50 values of 25 µg/mL for the extracts. Treatment with me Nostoc calcicola decreased the cell viability of HT-29 cells followed by consistent morphological changes leading to cytotoxicity. Nuclear condensation and DNA fragmentation were observed using AO/EtBr and DAPI staining. Flow cytometry analysis further confirmed the incidence of apoptosis during the S phase of the cell cycle. Furthermore, western blotting analysis confirmed the activation of caspase 9, a pivotal enzyme in the intrinsic apoptosis pathway, suggesting the ability of Nostoc calcicola to induce apoptosis in HT-29 colorectal cancer cells. Conclusion These findings underscore the potential of Nostoc calcicola as a valuable source of bioactive compounds with antioxidant and anticancer properties, warranting further investigation for their potential therapeutic applications in colorectal cancer. Graphical Abstract