Abstract
This study was undertaken to explore the antifungal activity of methanol (ME), acetone (AE) and methanol: acetone: diethyl ether (MADE) extracts of S. platensis, T. distorta, M. aeruginosa against seven phytopathogenic fungi (F. oxysporum, Fusarium sp., F. solani, A. flavus, A. niger, A. alternata, Alternaria sp. and Cladosporium sp.). All extract gave positive results against one or more tested fungi. However, none was able to inhibit the growth of A. alternata and Alternaria sp. Moreover, MADE of all three cyanobacteria showed stimulatory effect on these two fungi. ME, AE and MADE of S. platensis were found effective against maximum number of tested fungi. All extract were able to inhibit the growth of the Cladosporium sp. but with varying degrees. AE and MADE of S. platensis showed strong antifungal activity (+++) against F. oxysporum. Whereas, MADE of M. aeruginosa showed strong inhibitory effect against F. solani and Cladosporium sp. Crude extract (MADE) of all cyanobacteria metabolites was analyzed using gas chromatography-mass spectrometry (GC-MS). Results showed that the main component in the crude extracts of S. platensis is 2-hexyl-1-nitrocyclohexane (92.1 %); T. distorta is boronic acid, ethyl-, dimethyl ester (83.9 %) and M. aeruginosa is (S)-(+)-1-cyclohexylethylamine representing 91.9 %.