Efficiency of solvents in identification of bioactive compounds from selected marine red algae of the Gulf of Mannar, India

In the present study, three red algae samples, Acanthophora spicifera, Hypnea musciformis and Gelideilla acerosa, collected from Mandapam Coast, Gulf of Mannar, India, were extracted using polar solvents (Ethanol and Acetone) and non-polar solvents (Hexane and Chloroform). The crude extract of each alga was subjected to GCMS (Agilent 7890B; 5977A) analysis. A total of 288 compounds from all three red algae were identified. Of the 146 compounds identified in A. spicifera, 10 compounds have been commonly identified in all three solvents (hexane, ethanol and chloroform); another six compounds in ethanol and chloroform; five compounds in hexane and ethanol and another ten compounds in hexane and chloroform. Totally, 109 compounds have been identified in H. musciforms, only one compound, n-Hexadecanoic acid, was reported in all three solvents (hexane, ethanol and chloroform), and another 12 compounds have been commonly identified from ethanol and chloroform extracts. In G. acerosa, out of 151 compounds, seven compounds were identified commonly in ethanol and eleven in acetone and chloroform extracts. Overall the present study concludes that 32, 11, and 49 compounds identified were specific for hexane, ethanol and chloroform extracts of H. musciforms, respectively; 38, 27, and 42 compounds from ethanol, hexane and chloroform extracts of A. spicifera, respectively and exclusively 47, 35, and 35 different compounds in acetone, ethanol and chloroform extracts of G. acerosa, respectively. Therefore, the isolation of bioactive compounds is found to be polarity-specific. n-Hexadecanoic acid was the major constituent identified from A. spicifera in all three solvent extractions; in H. musciformis and in G. acerosa, only the acetone extract showed the highest peak area for n-Hexadecanoic acid. Seventy-one compounds identified through this study are yet to be reported in algae of India or elsewhere, and many of them have been found to have no report of biological activities. Therefore, these compounds would be evaluated, which will have a source for new drug candidates for communicable and non-communicable diseases. Further, the antimicrobial properties of crude extracts of all three red algae were tested using human pathogens (bacteria and fungi). The results revealed stronger antifungal activity against Candida sp. with hexane and chloroform extracts of H. musciformis and ethanol extracts of G. acerosa, whereas the antibacterial activity of H. musciformis extracts was stronger against all four human pathogenic bacteria than that of the other two red algae tested in this study. Therefore, the purification of compounds specific for antibacterial and antifungal properties from marine red algae may pave the way for new drug leads for the treatment of various human diseases.