Abstract

Cyanobacteria represent a promising but underexplored source of novel bioactive compounds for food and therapeutic applications. This study investigated the chemical profile and bioactivities of a methanolic extract from Phormidium species isolated from the Marakkanam salt pan (Tamil Nadu, India). Gas chromatography- mass spectrometry (GC-MS) analysis revealed a diverse chemical composition dominated by a major sesquiterpenoid (9.13% relative abundance), alongside fatty acids, phenolic derivatives, and other secondary metabolites. The extract demonstrated significant, dose-dependent biological activity in vitro. It exhibited potent α-amylase inhibition, with activity increasing from 14.39 ± 2.22% at 10 μg/mL to 72.05 ± 1.67% at 50 μg/mL. Concurrently, it showed strong free radical scavenging capacity in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, with inhibition ranging from 12.55 ± 2.15% at 25 μg/mL to 83.99 ± 1.49% at 200 μg/mL. However, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays on normal cell lines (MCF-10A and L929) revealed a significant dose-dependent cytotoxic effect, reducing viability to 32.73 ± 3.09% and 47.46 ± 2.24% at 200 μg/mL, respectively. These results confirm the extract as a rich source of bioactive molecules with pronounced anti-diabetic and antioxidant potential, while highlighting its cytotoxic effects on normal cells, which presents a critical limitation for direct therapeutic use. This underscores the necessity for compound purification to isolate specific agents with a safer therapeutic profile for future development in functional food ingredients or nutraceuticals.

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