Exploring the therapeutic potential of Kirkia tenuifolia Engl. stem bark extract and its bioactive compounds through experimental and computational approaches

Kirkia tenuifolia Engl. (family Kirkiaceae) is traditionally used to treat cholera, alleviate thirst, and serves as an important water source and livestock feed in arid regions. However, to date, no scientific study has been conducted on its chemical composition and pharmacological properties. Therefore, the present study aimed to isolate and identify the chemical constituents from the stem bark of Kirkia tenuifolia Engl and evaluate their pharmacological activities. Silica gel chromatographic separation of the methanol extract afforded nine compounds (1-9), identified herein for the first time from this species. Among them, lupeol (2) exhibited notable antibacterial activity with an MIC of 0.625 mg/mL against E. coli, S. typhi, and P. aeruginosa. Dimethylfraxetin (5), urolithin M5 (6) and urolithin M5 (7) showed antibacterial activity with an MIC of 0.625 mg/mL against E. coli and P. aeruginosa. Compounds 2, 5, 6, and 7 demonstrated potent antioxidant activities in the DPPH assay, with IC₅₀ values ranging from 2.58 to 9.00 µg/mL. The methanol extract showed significant cytotoxicity against MCF-7 breast cancer cells (34.96% viability at 200 µg/mL) and antiviral activity against influenza A (H1N1) (CC₅₀ = 39.8, IC₅₀ = 4.2 µg/mL, SI = 9.1). Molecular docking revealed that compound 7 exhibited higher binding affinities with S. aureus pyruvate kinase (-7.2 kcal/mol) and L. monocytogenes receptor (-7.4 kcal/mol) compared to ciprofloxacin (-5.6 and - 6.2 kcal/mol, respectively). Lupeol (2) showed stronger binding to Prdx5 (-6.1 kcal/mol) than ascorbic acid (-5.2), while compounds 2, 5, 6, and 7 bound more strongly to human myeloperoxidase (-7.4 to -8.6) than ascorbic acid (-4.8). These findings support the therapeutic potential of Kirkia tenuifolia Engl, but further studies are needed to confirm its effects against diverse pathogens and cell lines.