Bioactive Compound from Endophytic Fungus Trichoderma sp. Isolated from Cashew (Anacardium occidentale) Leaves

Anacardium occidentale, commonly referred to as cashew, serves an important function in agriculture and healthcare sectors. The leaves of A. occidentale are valued as a vegetable and have applications in traditional medicinal practices. This study analyzed the antioxidant and antibacterial properties, along with bioactive compounds synthesized by endophytic fungi that exist in a symbiotic relationship within the leaf tissues of A. occidentale. The endophytic fungi were isolated from A. occidentale leaves using PDA (Potato Dextrose Agar) media and identified morphologically. Each pure isolate was cultured in Potato Dextrose Broth (PDB) medium for a duration of 4 weeks at ambient temperature under stable conditions. Following this incubation phase, the liquid culture was separated from the biomass and subjected to extraction with ethyl acetate, which was then evaporated to yield a concentrated extract. Each of these concentrated extracts was assessed for antioxidant properties using the DPPH (2,2-diphenyl-1-picrylhydrazyl) assay and for antibacterial properties using the disk diffusion technique. Active extracts were further separated using chromatography techniques to isolate pure compounds, which were subsequently characterized by 1D and 2D NMR spectroscopy. This study identified 6 endophytic fungi (LM1 - LM6), comprising 3 Trichoderma sp. (LM1, LM2 and LM6), 1 Aspergillus sp. (LM3), 1 Nigrospora sp. (LM4) and 1 Penicillium sp. (LM5) based on morphological analysis. The antioxidant and antibacterial assays revealed that LM2 and LM4 demonstrated potent antioxidant effects and significant antibacterial efficacy against all bacterial strains tested. The LM2 isolate was selected for further bioactive compound isolation due to its higher extract yield. Chromatographic separation resulted in a pure yellow solid compound identified as a phenolic derivative, which showed weak antioxidant activity but demonstrated potent antibacterial effects against Bacillus subtilis and Salmonella typhi. Therefore, the endophytic fungus Trichoderma sp. (LM2) shows potential for development in the form of an extract or as a pure compound with structural modifications. HIGHLIGHTS We found endophytic fungi isolated from leaves of Anacardium occidentale. Trichoderma sp. (LM1), selected endophytic fungus, has the best antibacterial and antioxidant properties. The pure compound that was successfully isolated from the Trichoderma sp. is 7-hydroxy-6H-benzo[c]chromen-6-one GRAPHICAL ABSTRACT