Microalgae of different phyla display antioxidant, metal chelating and acetylcholinesterase inhibitory activities

Methanol and hexane extracts from Tetraselmis chuii, Nannochloropsis oculata, Chlorella minutissima and Rhodomonas salina were evaluated for total phenolic contents, radical scavenging activity (RSA), metal chelating potential against copper and iron ions and acetylcholinesterase (AChE) inhibition. Only the methanol extracts contained phenolic compounds. The hexane extracts had the highest RSA. The extracts had a higher capacity to chelate Fe²⁺ ions, more pronounced in the lowest concentration of the hexane extracts with values ranging from 73.3±3.3% (R. salina) to 97.5±1.1% (N. oculata). The highest AChE inhibitory activity was found in the hexane extracts at 10mg/ml of C. minutissima (79.3±1.9%), T. chuii (85.7±0.7%) and R. salina (81.5±7.5%). GC-MS analysis indicated polyunsaturated fatty acids and steroids as the most abundant compounds in the hexane extracts. The species under study provide a valuable source of antioxidants, metal chelators and AChE inhibitors.