Isolation, structural characterization and antimicrobial evaluation of 2-(1,7-dihydroxy-2,6-dimethylhexyl)-4H-chromen-4-one from Cassia fistula fruits

A chromone derivative (P1) was isolated from the chloroform extract of Cassia fistula fruits through silica gel column chromatography and characterized by FTIR, 1H NMR, 13C NMR, DEPT-135, HMBC, and LC-MS/MS analyses. Spectroscopic data confirmed the presence of a hydroxylated 2-substituted chromone skeleton with the molecular formula C₁₈H₂₄O₄. The antimicrobial activity of P1 was evaluated against selected bacterial and fungal strains using the agar disc diffusion method, where the compound exhibited moderate antibacterial activity against Staphylococcus aureus, Bacillus subtilis, Salmonella typhimurium, and Escherichia coli, with inhibition zones ranging from 12.3 ± 0.6 to 18.3 ± 0.6 mm, while significant antifungal activity was observed against Trichoderma harzianum and Aspergillus niger, showing inhibition zones of 27.7 ± 0.6 and 19.3 ± 0.6 mm, respectively. Molecular docking studies further demonstrated favorable binding affinities (-6.2 to -8.3 kcal/mol) against antibacterial, antiviral, and antifungal target proteins through hydrogen bonding, π–π stacking, alkyl, and π-alkyl interactions with key amino acid residues. Among the investigated targets, the strongest binding interaction was observed with the viral protein 9 × 2O (-8.3 kcal/mol). These findings suggest that the isolated chromone derivative possesses promising broad-spectrum antimicrobial potential and may serve as a potential lead compound for future drug development.