In vitro and in vivo antioxidant potential of the methanol extract, its fractions and isolated compounds of Piliostigma thonningi

Abstract

BackgroundIn Africa, Piliostigma thonningii is utilized traditionally for the treatment of dysentery, diarrhea, and various stomach complications. PurposeThe study's aim is the screening of the extract/fractions of P. thonningii for antioxidant activities and isolation of some of the components. MethodsThe root bark was extracted with methanol and subjected to further purification using liquid-liquid partitioning and chromatographic techniques. The isolated compounds were characterized by utilizing HPLC-DAD and 1D NMR spectroscopy. ResultsThe ethyl acetate fraction displayed best activity with total phenol content of 270 mgGAE/g, IC50 of 60.24 µg/ml (2,2-diphenyl-1-picrylhydrazyl (DPPH) assay) and EC50 of 653.4 µg/ml (ferric-reducing antioxidant power (FRAP) assay). For the in vivo antioxidant assay at 200 and 400 mg/kg, the ethyl acetate fraction produced significant (p < 0.05) inhibition of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) enzyme and lipid peroxidation activities just like 100 mg/kg silymarin, and also showed significant (p < 0.05) increase in serum antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD). Five known compounds, which include 4-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid, (2E)-3-(4‑hydroxy-3-methoxyphenyl)prop‑2-enoic acid, 8-(β-D-glucopyranosyl)-4′,5,7-trihyroxyflavone and (3αR,9R,9αs)-7‑hydroxy-9(4‑hydroxy-3-methoxyphenyl)-6‑methoxy-3α,4,9,9α-tetrahydro-1H-benzo[f][2]benzofuran-3-one were detected from HPLC-DAD analysis of the active fractions. Compound 6 (anabellamide) and 7 (9-desoxy-α-conidendrin) were isolated and they showed lower inhibition of DPPH radical compared to the extract and ethyl acetate fraction from where they were isolated. ConclusionThis study revealed the potential of the P. thonningii root bark as a source of antioxidant molecules which can be applied in therapy.