Anti-microbial and anti-cancer activity of Setosphaeria monoceras, an endophytic fungus associated with tropical mangrove plant

Abstract

Endophytes are a promising resource of pharmaceutically and agriculturally valuable secondary metabolites. Screening and isolation of endophytic fungi associated with the predominant mangrove plant Rhizophora apiculata from Chorao Island, Goa was undertaken. Eleven fungal strains were isolated, out of which one dominant strain was selected for phenotypic and genotypic identification. Based on 18S DNA gene sequencing, the fungus revealed 100% homology with Setosphaeria monoceras, a teleomorph of Exserohilum monoceras. GC-MS analysis of crude compounds extracted with ethyl acetate revealed the presence of sulfurous acid, 2-ethylhexyl isohexyl ester, heptacosane, dodecyl pentyl ester, eicosane, 2-methyl and 2-bromotetradecane. Ethyl acetate extracted crude metabolites of this isolate was screened for antimicrobial activity against seven common human pathogenic bacteria viz., Shigella boydii, Klebsiella pneumonia, Escherichia coli, Staphylococcus aureus and Salmonella enterica. However, no antifungal activity was noticed against Aspergillus brasiliensis and Candida albicans. Diameters of inhibition zones measured in the plate assay were significantly high (20-50mm). MIC values were between 3.12 to 6.25 ?g/mL. The extract revealed strong bactericidal effect against the test bacterial pathogens. The aliquots on testing against human lung cancer cell line A-549 showed significant anti-cancer activity compared with the activity exhibited by the standard drug cisplatin. This study supports the belief of conferring the potential attributes of endophytic fungi associated to tropical estuarine as Setosphaeria monoceras showed impressive bioactivities which may be exploited for novel bioactive compounds. This is the first antimicrobial study to be undertaken on this relatively novel estuarine endophytic fungal strain from the rich and diverse Chorao mangrove habitat.