Numerous biologically active metabolites have previously been obtained from endophytes including endophytic fungi. This potentiality and prospect prompted us to find out new compounds having activity against pathogenic bacteria, from fungal endophyte, Necterium sp. isolated from the leaf of Tinospora cordifolia. We cultivated and developed the fungal strains on PDA medium and extracted on ethyl acetate after 28 days. Column chromatographic technique followed by preparative TLC was utilized to isolate secondary metabolites as pure crystalline solid. Two naphthoquinones namely anhydrofusarubin (1) and fusarubin methyl ether (2) were isolated from Necterium sp. The 1H and 13C NMR spectral data of the isolated compounds were analyzed and compared with previously published values to confirm the structure of the compounds. The compounds were assessed for antibacterial activity by resazurin based microdilution assay. Both of them showed sensitivity towards gram negative Pseudomonas aeruginosa but none was active against Staphylococcus aureus, a gram positive bacteria. The MIC values against P. aeruginosa for anydrofusarubin (1) and fusarubin methyl ether (2) were found to be 32- and 64-μg/ml respectively while the standard gentamycin showed MICs of 6.25 μg/ml (for S. aureus) and 12.5 μg/ml (for P. aeruginosa). The outcomes of our study suggest that anhydrofusarubin (1) and fusarubin methyl ether (2) are beneficial lead compounds to broaden the sphere of marketed antibacterial drugs.
Bangladesh Pharmaceutical Journal 25(1): 80-88, 2022 (January)
Endophytes provide mutual benefits and produce various biologically active secondary metabolites in plants. Our study was designed to isolate and identify fungal endophytes from fresh leaf and bark of Tinospora cordifolia, coupled with their bioactivity and preliminary chemical screening. Six endophytic fungi were isolated using surface sterilization technique. The fungi were identified by microscopic and molecular characterization and confirmed TCLE-1 as Fusarium perseae, TCLE-2 as Fusarium keratoplasticum, TCLE-3 as fusarium macrosporum, TCBE-1 as Fusarium falciforme and TCBE-2 as well as TCBE-3 leaving unidentified. Isolated strains were cultured in large scale on potato dextrose agar (PDA) medium and were extracted using ethyl acetate. Antibacterial activity of fungal extracts was performed by disc diffusion method and cytotoxicity using HeLa cell line by MTT assay. In antimicrobial test, all the fungal extracts except TCBE-2 showed moderate to potent activity in comparison to the standard kanamycin. All, except TCBE-2, demonstrated significant cytotoxic activity on HeLa cell. Preliminary chemical profiling using thin liquid chromatography (TLC) and analytical high performance liquid chromatography techniques indicated the presence of secondary metabolites in fungal extracts. In conclusion, endophytic fungi reside in the T. cordifolia, a native medicinal plant in Bangladesh, could be a potent source of putative antibacterial and anticancer compounds.
Dhaka Univ. J. Pharm. Sci. 21(2): 183-194, 2022 (December)
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