In vitro antibacterial, antioxidant, in silico molecular docking and ADEMT analysis of chemical constituents from the roots of Acokanthera schimperi and Rhus glutinosa

Abstract

Abstract Acokanthera schimperi is a medicinal plant traditionally used for the treatment of wounds, scabies, and malaria. Rhus glutinosa has been also utilized for the management of ectoparasites and hemorrhoids. Silica gel column chromatography separation of CH2Cl2/MeOH (1:1) extract root of A. schimperi afforded oleic acid (1), lupeol (2), dihydroferulic acid (3), acovenosigenin A- 3-O-α-L-rhamnopyranoside (4) and sucrose (5) whereas CH2Cl2/ MeOH (1:1) and MeOH roots extracts of R. glutinosa afforded β-sitosterol (6), (E)-5-(heptadec-14-en-1-yl)-4,5-dihydroxycyclohex-2-enone (7), methyl gallate (8), and gallic acid (9). The structures of the compounds were established using spectroscopic (1D and 2D NMR) and FT-IR techniques. Disc diffusin and DPPH assay were used, respectively, to evaluate the antibacterial and antioxidant potential of the extracts and isolated compounds. MeOH extract root of A. schimperi showed a modest antibacterial effect against E.coli with an inhibition zone (ZI) of 16 ± 0.0 mm compared to ciprofloxacin (ZI of 27.0 ± 0.0 mm). CH2Cl2/MeOH (1:1) and MeOH root extracts of R. glutinosa showed maximum activity against S. aureus with ZI of 17.3 ± 0.04 and 18.0 ± 0.0 mm, respectively. At 5 mg/mL, the highest activity was noted against S. aureus by 8 with ZI of 18.6 ± 0.08 mm. Dihydroferulic acid (3), methyl gallate (8), and gallic acid (9) displayed potent scavenging of DPPH radical with respective IC50 of 10.66, 7.48, and 6.08 µg/mL, compared with ascorbic acid (IC50 of 5.83 µg/mL). Molecular docking results showed that lupeol (2) exhibited strong binding energy of -7.7 and − 10 kcal/mol towards PDB ID: 4F86 and PDB ID: 3T07, respectively, compared to ciprofloxacin (-6.5 and − 7.2 kcal/mole). Towards PDB ID: 1DNU receptor, compounds 3, 8, and 9 showed minimum binding energy of -5.1, -4.8, and − 4.9 kcal/mol, respectively, compared to ascorbic acid (-5.7 kcal/mol). The Swiss ADME prediction results indicated that compounds 2, 3, 8, and 9 obeyed the Lipinksi rule of five and Veber rule with 0 violations. The in vitro antibacterial and antioxidant results supported by in silico analysis indicated that compounds 2, 3, 8, and 9 can potentially be lead candidates for the treatment of pathogenic and free radical-induced disorders.

Keywords

• Antibacterial
• Antioxidant
• Molecular docking
• Binding energy