Bionectria ochroleuca NOTL33—an endophytic fungus from Nothapodytes foetida producing antimicrobial and free radical scavenging metabolites

Abstract

Endophytic fungi are reported to produce diverse classes of secondary metabolites. This study investigated the antimicrobial and free radical scavenging activity of a foliar endophytic fungus from Nothapodytes foetida, a medium sized tree known to produce the antineoplastic compound camptothecin. The fungal isolate was identified as Bionectria ochroleuca based on the ITS rDNA analysis. The differences among endophytic, pathogenic and free living Bionectria ochroleuca were established by RNA secondary structure analysis. The metabolites showed a broad spectrum of antibacterial, antifungal and anti-dermatophytic activity. Minimum inhibitory concentration values of ethyl acetate extracts were in the range of 78–625 μg/mL against all test organisms, except for Pseudomonas aeruginosa (5 mg/mL). Antimicrobial components in the ethyl acetate extract were identified by GC-MS analysis. The isolate was also produced volatile antifungal compounds. A dose-dependent free radical quenching was observed in the ethyl acetate extract. This is the first report on Bionectria sp. as an endophyte of N. foetida. The results indicate that the B. ochroleuca NOTL33 isolate is a potential source of antimicrobial agents and could be used as an effective biofumigant.