Molecules 2019 Mar 3;24(5). Epub 2019 Mar 3.
Chemical Engineering, CSIR, CIMAP, Kukrail Picnic Spot Road, Lucknow 226016, India.
This paper reports the successive isolation and purification of bioactive compounds from the stem bark of , a widely known medicinal plant. The ethyl acetate extract of the stem bark exhibited the strongest antioxidant activity assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging, and ferric reducing antioxidant power (FRAP) assays (IC = 46.7, 66.0, and 492.6, respectively). By column chromatography (CC) with elution of hexane and ethyl acetate at 8:2, 7:3, and 6:4 ratios, the isolation of this active extract yielded five fractions (⁻). Chemical structures of the constituents included in ⁻ were elucidated by gas chromatography-mass spectrometry (GC-MS), electrospray ionization-mass spectrometry (ESI-MS), and nuclear magnetic resonance (NMR) and resolved as methyl gallate (, , , ), gallic acid (, ), fraxetin (, , , ), and tomentin (). Mixture (IC DPPH and ABTS = 2.5 µg/mL) and (IC FRAP = 381 µg/mL) showed the highest antioxidant properties. Among the isolated fractions, was the most potential agent in growth inhibition of six bacterial strains including , , , and (MIC = 5, 20, 30, 20, 25, and 20 mg/mL, respectively). All identified constituents exerted an inhibitory activity on the growth of , of which the mixture performed the maximal inhibition on shoot (IC = 49.4 µg/mL) and root (IC = 47.1 µg/mL) growth. Findings of this study suggest that gallic acid, methyl gallate, fraxetin, and tomentin isolated from possessed antioxidant, antibacterial, and growth inhibitory potentials.