Antimicrobial Activity of Secondary Metabolites from Endophytic Fungi Isolated from Nerium Oleander L

Endophytic fungi found inside the plant tissue are endosymbionts, protecting their host from pests, pathogens, etc. Twenty eight endophytic fungi were isolated from different parts of Nerium oleander L., out of which, 54% of isolates were from flower, 39% from stem and 7% from leaf parts. Thirty six percent of the isolates showed antimicrobial activity against tested pathogens. The potential isolates such as Fusarium semitectum (Nof-3), Colletotrichum gloeosporioides (Nof-7), Alternaria alternata (Nof-8) and Mycelia Sterilia sp.1 (Nos-6) were subjected to the production and extraction of secondary metabolites. All the four fungal extracts inhibited Staphylococcus aureus and Bacillus cereus at 20 μg/mL (MIC). Extracts of C. gloeosporioides and Mycelia Sterilia sp.1 showed activity against Pseudomonas aeruginosa at MIC of 20 μg/mL. The growth of Escherichia coli was suppressed by all the tested extracts at MIC of 20 μg/mL except F. semitectum. A. alternata & Mycelia Sterilia sp.1 extracts were active against Salmonella typhimurium at 20 μg/mL. The growth of Candida albicans was inhibited by Mycelia Sterilia sp.1 at 20 μg/mL. The zones of inhibition were statistically significant with respective positive controls.