Exploration of antioxidant activities, microstructural properties, and fatty acid composition of three cyanobacteria species

Cyanobacteria have gained increasing attention in the food and pharmaceutical industries as a natural source of antioxidants. However, more knowledge is needed regarding the antioxidant and nutritional properties of cyanobacteria found in water bodies worldwide, including those in Sri Lanka. This study investigated the antioxidant activities and microstructural properties using FTIR-ATR (Fourier Transform Infrared Spectroscopy-Attenuated total reflectance) analysis and the fatty acid composition of three cyanobacterial species: Chroococcidiopsis sp., Gleocapsa sp., and Merismopedia sp., which were isolated from water bodies in Sri Lanka. The water extract of Chroococcidiopsis sp. Exhibited the highest (p <= 0.05) phenolic content (2.26 +/- 0.09 mg GAE/g DW) and ABTS activity (13.28 +/- 0.36 mmol TE/g DW) among the tested species. The methanol extract of Merismopedia sp. Displayed the highest (p <= 0.05) DPPH activity (IC50-15.21 mg/mL) and notable (p <= 0.05) ORAC values (112.50 +/- 5.79 mmol TE/g DW). Analysis by FTIR-ATR revealed the presence of nutritional components, including proteins, lipids, and polysaccharides, as well as functional compounds such as phenolics and amides in the studied cyanobacterial species. The fatty acid composition indicated that the studied cyanobacteria contain twenty different saturated and unsaturated fatty acids, with compositions ranging from 60 to 70% and 29-39%, respectively. Saturated fatty acids, caprylic, capric, pentadecanoic, heptadecanoic, palmitic, and lignoceric acids, were detected in all species, while elaidic, palmitoleic, and Cis-10- heptadecanoic acids were identified as prominent monounsaturated fatty acids among them. Gleocapsa sp. Had the highest (p <= 0.05) saturated fatty acid content, while Merismopedia sp. Showed the highest (p <= 0.05) unsaturated fatty acid content. Based on the results, Merismopedia sp. Has demonstrated promising potential as a rich source of antioxidants and unsaturated fatty acids.