Antibacterial and Antioxidant Activity of Isoflavans from the Roots of Rhynchosia ferruginea and In Silico Study on DNA Gyrase and Human Peroxiredoxin

Abstract

Rhynchosia ferruginea (Udusalim, Afan Oromo) is a medicinal plant traditionally used to treat skin infection, intestinal problems and amoebiasis. Silica gel chromatographic separation of dichloromethane/methanol (1:1) roots extract yielded isoflavan (1), isoflavene (2) and 1, 3-dilinoleoyl-2-stearoylglycerol (3), reported herein for the first time from the genus. Antibacterial activity was examined using disc diffusion method against E. coli, S. aureus, P. aeruginosa and S. pyogenes. AutoDoc vina 4.2 soft ware was used for molecular docking analysis of compounds against human peroxidoxin 5 and DNA gyrase B enzymes. Isoflavan (1) displayed zone of inhibition of 9.67 ± 0.58 mm and 10.67 ± 0.58 mm whereas isoflavene (2) showed 10.33 ± 1.15 mm and 10 ± 1.00 mm against E. coli and S. aureus, respectively, compared to ciprofloxacin (15.67±0.58 mm for both strains). DPPH radical scavenging assay of the dichloromethane/methanol (1:1) roots extract and isoflavan (1) exhibited better radical scavenging activity with IC50 value of 17.7 and 32, respectively. Molecular docking analysis revealed that 1 and 2 exhibited similar binding affinity of -7.4 kcal/mol compared to ciprofloxacin (-7.3 kcal/mol). In silico analysis against human peroxidoxin 5 (PDB ID: 1HD2) revealed minimum binding affinity of - 3.7 and - 2.0 kcal/mol for compounds 1 and 2, respectively, compared to ascorbic acid (-4.9 kcal/mol). The in vitro antibacterial and antioxidant activity of compounds 1 and 2 suggest the potential use of these compounds as drug lead candidates which corroborate with the traditional uses of the roots of R. ferruginea.