Evaluation of the Antibacterial and Antioxidant Properties of Chemical Constituents of the Roots of Woodfordia uniflora: An Integrated Approach of Experimental and Computational Study.

Abstract

Woodfordia uniflora is a medicinal plant used for the treatment of malaria, toothache, and stomach problems. The root parts of the plant are also used for healing liver disorders. Silica gel chromatography separation of CH₂Cl₂/MeOH (1:1) and MeOH extracts of roots of W. uniflora result in the isolation of three compounds, namely, bergenin (1), β-sitosterol (2), and epigallocatechin 3-gallate (3), reported herein for the first time from the plant. The structure of the isolated compounds was elucidated using NMR (1D and 2D) techniques. Disk diffusion and DPPH assay were used to evaluate the antibacterial and antioxidant activities, respectively. Molecular docking was done by the AutoDock Vina 4.2 program. The pharmacokinetics and toxicity profile of compounds were predicted by Swiss ADME and Pro Tox II online servers. GC-MS analysis roots of W. uniflora result in the identification of five compounds, of which palmitic acid (34.9%) was the major constituent. The antibacterial activity result indicated that the oil extract had promising activity against P. aeruginosa, E. coli, S. pyogenes, and S. aureus with IZ of 14.3 ± 0.81, 15.0 ± 0.0, 15.6 ± 0.47, and 17.6 ± 0.47 mm, respectively, at 5 mg/mL, compared to ciprofloxacin (1Z 27-30.0 ± 0.0 mm) at 30 μg/mL. MeOH and CH₂Cl₂/MeOH (1:1) extract showed inhibition against E. coli (IZ of 13.6 ± 0.47 mm) and P. aeruginosa (IZ of 10.0 ± 0.0 mm), respectively, at 200 mg/mL. Bergenin (1) and β-sitosterol (2) also displayed maximum inhibition of E. coil (IZ of 11.6 ± 0.47) and S. aureus (11.0 ± 0.0 mm), respectively, at 5 mg/mL. The antioxidant activity results showed that CH₂Cl₂/MeOH (1:1) and MeOH extracts, bergenin (1), and compound 3 displayed potent scavenging DPPH radical with a percentage of inhibition of 76.8 ± 0.12, 77.8 ± 0.08, 71.4 ± 0.08, and 91.2 ± 0.16, respectively, compared to ascorbic acid (93.2% ± 0.04%) at 100 μg/mL. The molecular docking analysis showed that all compounds (1-3) exhibited minimum binding energy toward PDB ID: 1HD2 (-5.2 to -6.3 kcal/mol), compared to ascorbic acid (-5.6 kcal/mol), and toward PDB ID: 1DNU (-8.0 to -10.7 kcal/mol) receptors, compared to ascorbic acid (-5.7 kcal/mol). Toward the PDB ID: 4FM9 receptor, β-sitosterol (2) and compound 3 exhibited the best binding free energy of -9.1 and -9.8 kcal·mol, respectively, compared to vosaroxin (-7.8 kcal/mol). The drug-likeness analysis result indicated that bergenin (1) and β-sitosterol (2) obeyed four and five criteria of Lipinski's rule, respectively, and are more likely to be administered orally. The in silico toxicity analysis showed none of the compounds would be cytotoxic, mutagenic, or hepatotoxic. The in vitro antioxidant and antibacterial results supported by in silico analysis demonstrated that the roots of W. uniflora have the potential to be therapeutic agents for bacterial infections and free radical-inducing diseases.