Successive solvent extraction and GC–MS analysis for the evaluation of the phytochemical constituents of the filamentous green alga Spirogyra longata

Spirogyra species are one of the most common freshwater filamentous green algae reported to have antimicrobial activities. However, their chemical constituents have not been entirely detected. In this work, the chemical constituents of Spirogyra longata, successively extracted with petroleum ether, methylene chloride, chloroform, acetone and methanol were determined by GC–MS. The extract percentage varied greatly between different solvents, with the highest one (4.83%) recorded for methanol. A total of 97 compounds were identified in different extracts, out of which there were, 5 alkaloids, 6 ketones, 8 terpenes, 4 phenolics, 20 hydrocarbons, 4 fatty acids, 5 fatty alcohols, 20 esters, 7 sterols and 18 others. Generally, the composition and mass fraction of phytochemical constituents in S. longata extracts were affected by the extraction solvent, in which, the ketone hexahydrofarnesylacetone and the phenolic, butylated hydroxytoluene (BHT) were dominant in S. longata chloroform extract with peak area% of 17.38 and 50.7. Meanwhile, neophytadiene and phytol were the dominant terpenes in methylene chloride extract with a peak area percentage of 24.32 and 30.43, while, hydrocarbons (C10–C29) and sterols were found to maintain 0.624% and 0.46% of S. longata DW and were mainly detected in petroleum ether extract. Alkaloids were only detected in acetone and methanol extracts and comprise 0.399% of S. longata DW. Moreover, fatty acids and esters were found to represent about 30% of the total extracts, and were dominated by palmitic acid and its methyl and ethyl esters. In conclusion, S. longata was found to contain a variety of valuable compounds, which reflect its pharmaceutical and biofuel potentialities.