Synechocystis salina: potential bioactivity and combined extraction of added-value metabolites

Few studies have focused on the biotechnological potential of the marine cyanobacterium Synechocystis salina, in particular its bioactive metabolites. Hence, an opportunity exists to explore various solvent combinations in attempts to improve extraction of cellular contents of metabolites with antioxidant features as a part of a structured attempt to determine whether S. salina LEGE 06,155 holds a promise for industrial exploitation. Extracts were obtained by single extractions with four GRAS solvents: hexane (H), acetone (A), ethanol (E), and buffer phosphate (PBS) (series A) and successive extractions: H-E-PBS (series B), H-A-PBS (series C), and H-A-E-PBS (series D). The yields, antioxidant capacity, and cytotoxicity of the extracts, as well their content in pigments, lipids, and phenolic compounds were assessed. The combination of solvents of series B produced the highest yield of extraction, of 33.56%. Aqueous extracts for single (series A) and successive extractions (series B and C) presented the highest antioxidant capacity, for ABTS•⁺ and NO•⁻, respectively, and had a high content of phycobiliproteins (PBPs). The acetonic (series A) and ethanolic (series B) extracts also showed high antioxidant capacity, in particular for DPPH• and O₂•⁻, respectively. Overall, organic extracts did not show signs of cytotoxicity. Series B extraction enhanced general pigment content, yet single extraction with ethanol (series A) produced the highest content in carotenoids, in particular echinenone and β-carotene, and PBS (series A) improved PBPs content. The lipid content was enhanced in series A (ethanol), while the total phenolic content was improved in series B. Synechocystis has accordingly demonstrated potential for eventual exploitation as biotechnological resource, in terms value-added compounds with antioxidant features.