Abstract
Endophytic fungi, which colonize within a host plant without causing any apparent diseases, have been considered as an important source of bioactive secondary metabolites containing antimicrobial and antioxidant activities. The aim of this research was to isolate the endophytic fungi of Cinnamomum loureiroi and then to screen their antimicrobial and antioxidant activities. A total of 11 fungal endophytes were isolated from healthy leaves of Cinnamomum loureiroi belonging to six genera: Botryosphaeria, Colletotrichum, Diaporthe, Fusarium, Neopestalotiopsis, and Pestalotiopsis. All isolated strains were cultured and further extracted with ethyl acetate solvent. Antimicrobial activity of all crude endophytic fungal extracts was analyzed using disc diffusion assay against six bacterial and two fungal pathogens. Crude extracts of strains MFLUCC15-1130 and MFLUCC15-1131 showed broad-spectrum antimicrobial activity against all tested pathogens. Activity against Bacillus cereus and Staphylococcus epidermidis was notable, showing the lowest minimum inhibitory concentration at 3.91 μg/mL. Antioxidant activity of all crude endophytic fungal extracts was also evaluated based on 2,2-diphenyl-1-picrylhydrazyl assay. Significant antioxidant activity was detected in the crude extracts of fungus MFLUCC15-1130 and MFLUCC15-1131 with IC50 of 22.92 ± 0.67 and 37.61 ± 0.49 μg/mL, respectively. Using molecular identification, MFLUCC15-1130 and MFLUCC15-1131 were identified as Neopestalotiopsis sp. and Diaporthe sp., respectively. The major chemical constituents produced by both crude extracts were identified by gas chromatography-mass spectrometry. Eugenol, myristaldehyde, lauric acid, and caprylic acid were the primary antimicrobial and antioxidant compounds in both crude extracts. This is the first report of eugenol being a biologically active compound of Neopestalotiopsis sp. and Diaporthe sp. fungal endophytes. Eugenol has been reported as antimicrobial and antioxidant agents with agronomic applications. Thus the two newly-isolated endophytes may be used for eugenol production, which in turn can be used in a variety of applications.
Highlights
Endophytes, mostly identified as fungi and bacteria, are microorganisms residing inside healthy plant hosts without causing any apparent negative effects (Strobel et al, 2004)
It was noted that all fungal extracts in this study demonstrated antimicrobial activity on some microbial pathogens, Gram-positive bacteria, Gram-negative bacteria, fungi, or yeast (Gouda et al, 2016)
This study presents a broad spectrum of antimicrobial activities of crude fungal extracts from Cinnamomum loureiroi leaves
Summary
Endophytes, mostly identified as fungi and bacteria, are microorganisms residing inside healthy plant hosts without causing any apparent negative effects (Strobel et al, 2004). Individual plant species may be a host to at least one endophytic fungus, the potential of discovering novel endophytic species is high. The relationship between fungal endophytes and plant hosts is intimate. Bioactive metabolites produced by fungal endophytes may be applied as sources of novel natural products for exploitation in agriculture, medicine, and other industries (Strobel et al, 2004). Given the broad range of endophytic fungi and their metabolic potential, there are good opportunities to investigate new endophytes colonizing medicinal plants in different ecosystems
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