Abstract
BackgroundPlants with an ethnobotanical history are known to harbor diverse group of endophytic fungi, which constitute major natural sources of bioactive compounds. In the present study, we evaluated the antioxidant activity of endophytic fungi from eight Nigerian ethnomedicinal plants. Endophytic fungi were isolated from the leaves of Acalypha ornata, Albizia zygia, Alchornea cordifolia, Chrysophyllum albidum, Ficus exasperata, Gomphrena celosioides, Millettia thonningii, and Newbouldia laevis.MethodsEndophytic fungi were isolated from the leaves of selected plants via surface sterilization. Isolated fungi were identified by internal transcribed spacer (ITS-rDNA) sequence analysis. Pure fungal strains were subjected to fermentation process on solid rice medium and metabolites extracted using ethyl-acetate. Fungal crude extracts were screened for antioxidant activity using 2, 2- diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and reduction of ferric ion assays. Gas chromatography/mass spectrometry (GC/MS) analysis was used to identify the major chemical constituents in active fungal extracts.ResultsA total of eighteen fungal endophytes with fungal codes CU (061 and 062); ZA (161, 162, 163, and 164); LO (261); CA (041, 042, and 043); FE (081, 082, and 084); GE (091); MO (211 and 212); and NA (021 and 022) were isolated from the eight ethnomedicinal plants A. ornata, A. zygia, A. cordifolia, C. albidum, F. exasperata, G. celosioides, M. thonningii, and N. laevis respectively. ZA 163 and MO 211 fungal extracts showed significant (p < 0.05) radical scavenging activity with IC50 values of 50.53 ± 0.01 and 86.69 ± 0.02 μg/ml respectively. Fungal extract CA 041 demonstrated significantly (p < 0.01) higher iron chelating activity than standard gallic acid with absorbance values of 0.803 and 1.107 at 250 and 500 μg/ml concentrations respectively. Pyrogallol, phenol, 2,6-dimethoxy-, phytol, dl-alpha-tocopherol, alpha-tocospiro, oleamide, methyl stearate, oleic acid, palmitic acid, campesterol, stigmasterol, β-sitosterol, urs-12-en-24-oic acid, 3-oxo-, methyl ester, lup-20(29)-en-3-one, and lupeol were detected in the selected active extracts.ConclusionThese results showed that leaves of the selected Nigerian plants harbor diverse group of endophytic fungi, which can be potential antioxidant resource.Graphical abstract
Highlights
Plants with an ethnobotanical history are known to harbor diverse group of endophytic fungi, which constitute major natural sources of bioactive compounds
Isolation of endophytic fungi Eighteen pure fungal endophytes were successfully isolated from surface sterilized fresh leaf samples of eight medicinal plants: Acalypha ornata, Albizia zygia, Alchornea cordifolia, Chrysophyllum albidum, Ficus exasperata, Fig. 1 Pictures of selected plants from University of Lagos, main campus, Nigeria used for fungal isolation
Our results suggest that endophytic fungi that reside in the leaves of A. ornata, A. zygia, A. cordifolia, C. albidum, F. exasperata, G. celosioides, M. thonningii, and N. laevis showed promising antioxidant activity
Summary
Plants with an ethnobotanical history are known to harbor diverse group of endophytic fungi, which constitute major natural sources of bioactive compounds. Endophytic fungi from the genera Colletotrichum, Fusarium, Alternaria and Aspergillus, isolated from medicinally important plants exhibit a variety of biological activities such as anticancer, antimicrobial, antifungal, immunomodulatory, antitubercular, and antioxidant activities with wide application in agrochemical and pharmaceutical industries [5,6,7,8]. These biological activities demonstrated by endophytes have been attributed to isolated and identified secondary metabolites such as alkaloids, terpenoids, steroids, quinones, isocoumarin derivatives, flavanoids, peptides, and phenols present in the fungal extracts [9,10,11,12,13,14]. Exploring endophytic fungi that reside in medicinal plant species would provide vast opportunities to discover new medicinally important metabolites [15]
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