Characterization of endo-metabolome exhibiting antimicrobial and antioxidant activities from endophytic fungus Cercospora sp. PM018

Abstract

In the context of increasing demand for novel pharmaceutical high-value compounds and their natural sources, endophytic fungi from medicinal plants are being recently explored for diverse bioactive metabolites. We report bioprocess optimization and biochemical characterization of the endo-metabolome possessing broad-spectrum antimicrobial and antioxidant activities, from an endophytic fungus Cercospora sp. PM018 that was isolated from Lal-bisalyakarani (Aerva javanica Juss. Ex.Schult, an Indian indigenous medicinal plant). Potato dextrose medium having pH 4.0 and incubation temperature of 30 °C were found to be optimal for the enhanced bioactivities of the endo-metabolome after 12 days of fungal growth. In the antibiotic-potentiating assay, fractional inhibitory concentration <0.5 proved endo-metabolome's involvement in the synergistic antimicrobial activity due to the presence of mannitol as a crucial constituent. Bioassay-guided chromatographic separation and subsequent GC–MS analysis identified a few important antibacterial compounds, such as palmitic acid and stearic acid. Interestingly, it was deciphered that the host plant botanicals modulated the endophytic fungus to grow more at the expense of reduced bioactivities. A substantial change in fungal endo-metabolomic profile was observed in the presence of host botanicals, which might account for the reduced bioactivities. The reduction of bioactivities in terms of biocontrol features of Cercospora sp. for both host and non-host plants, implies the necessity of in-depth study on any endophyte (having bioactivities) before tagging them with biocontrol potential. On the contrary, owing to its diverse bioactive potentials, the endophytic Cercospora sp. PM018 has worthy future prospect to be utilized in the pharmaceutical and food industries.

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