Fungal endophytes isolated from the leaves of a medicinal plant, Ocimum sanctum Linn and evaluation of their antimicrobial activities

The endophytic fungi isolated from leaves of Ocimum sanctum Linn. of different ages were examined for antimicrobial activity. The agar plug diffusion assay was used for primary screening. A total of 148 fungal endophytes were successfully isolated and cultured but only 134 of them (90.5%) exhibited inhibitory activity towards at least one test microorganisms. Moreover, the colonization rate indicated that the old leaves were frequently and densely colonized by endophytes. The results suggested that healthy leaves at older stages of growth can be a potential source for the isolation of endophytic fungi with antimicrobial properties. The ethyl acetate extract prepared from the fermentative broth exhibited better antimicrobial activity and it suggested the antimicrobial activity of the isolates was affected by the culture medium. A better antimicrobial activity was observed in the yeast extract sucrose broth as compared to malt extract broth. Significant improvements in the antimicrobial activity of the crude extract were observed after addition of water extract of the host plant in the culture medium.