Characterization of metabolite compounds from endophytic fungi associated with white turi plant (<i>Sesbania grandiflora</i>) and their antibacterial activity

Abstract The emergence of resistance in pathogenic bacteria to synthetic antibiotics is a critical global issue. This study aims to isolate antibacterial compounds from endophytic fungi and characterize the secondary metabolites from the white turi plant ( Sesbania grandiflora (L.) Pers.) as a novel source of natural antimicrobial agents to combat the growing problem of antibiotic resistance. The research involved isolating fungi, testing bioactivity, and purifying and characterizing bioactive compounds. Nine endophytic fungal isolates were obtained from the plant’s stem, seed, leave, and flower tissues. The isolate with the strongest antibacterial activity (Code: Bt-12), was derived from the stem tissue, showing 48.49 % inhibition against Staphylococcus aureus and 42.06 % against Pseudomonas aeruginosa using the microdilution method. Purification using vacuum liquid chromatography (VLC) identified the NV42 fraction as having the most significant antibacterial effect, with inhibition zone of approximately 12.5 mm for S. aureus and 8 mm for P. aeruginosa using the disc diffusion method. Liquid chromatography-mass spectrometry (LC-MS/MS) characterization identified the highest peaks from three selected fractions at retention times of 7.65, 15.27, and 7.69, with corresponding molecular formulas of C 23 H 31 N 2 O 2 , C 38 H 74 NO 14 , and C 23 H 31 N 2 O 2 , respectively and were classified as alkaloid secondary metabolites. This research successfully identified the predicted bioactive compounds that inhibit the growth of pathogenic bacteria, providing valuable insights into potential antibacterial agents derived from endophytic fungi in turi plants.