Bioactive Compound from the Endophytic Fungus Paecilomyces variotii Isolated from the Stems of Physalis angulata L.

Physalis angulata L., also referred to as “ciplukan” locally, is well-known for its use in traditional medicine due to the presence of bioactive compounds. Considered to be promising sources of bioactive chemicals, endophytic fungi living symbiotically within P. angulata tissues warrant investigation. The purpose of this study is to identify and investigate the characteristics of extracts and bioactive compound of endophytic fungus isolated from stem of P. angulata. The morphological identification was the first step in the study. For 4 weeks, the fungi were grown in PDB medium at room temperature in static circumstances. After dividing the liquid medium with ethyl acetate and evaporating it to produce concentrated extracts, it extracts’ antibacterial and antioxidant properties were examined. The disc diffusion method was used to assess antibacterial activity, while the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay was used to investigate the antioxidant potential. From the chosen active extracts, bioactive molecules were separated using column chromatography method, and spectroscopic analysis was used to identify the chemical structures of these compounds. Additionally, molecular identification of the endophytic fungus isolates was carried out. Five endophytic fungi in all were identified, numbered CB1, CB2, CB3, CB4 and CB5. Morphological identification indicated that the fungi belonged to 3 genera: Papulaspora sp. (CB1, CB2, and CB4), Verticillium sp. (CB3), and Paecilomyces sp. (CB5). The antibacterial activity of all the fungal extracts was found to be moderate to weak, with isolate CB5 exhibiting the highest action against Staphylococcus aureus, Salmonella typhi, Escherichia coli, and Bacillus subtilis. Molecular analysis identified the CB5 isolate as Paecilomyces variotii. The pure compound isolated from this fungus was identified as 4,5,6-trihydroxy-2',3',5',6-tetramethyl-[3,4'-bipyranylidene]-2-one, which demonstrated significant antioxidant activity (IC50 23.82 μg/mL) and potent antibacterial effects (MIC < 100 μg/mL). These results demonstrate this endophytic fungus’s potential as a useful source of bioactive chemicals for the treatment of bacterial infections and oxidative diseases associated with stress. HIGHLIGHTS Cultivation of endophytic fungi from angulata stems can shorten the time to obtain compounds that are efficacious for medicine compared to using host plants. Paecilomyces variotii is an endophytic fungus from angulata stems with the strongest antibacterial activity compared to other fungi. This is evidenced by the percentage of inhibition of 70 - 85 % in all test bacteria. The antioxidant activity of variotii is in the moderate range (IC50 151.26 µg/mL). However, after isolation of pure compounds, strong antioxidant activity was obtained (IC50 23.82 µg/mL). The pure compound that was successfully isolated from the variotii fungus is 4,5,6-trihydroxy-2',3',5',6-tetramethyl-[3,4'-bipyranylidene]-2-one. GRAPHICAL ABSTRACT