Polyphenol Content and Antioxidant Activity of Bark Hydroethanolic Extract of Piliostigma reticulatum (DC) Hochst and Its Fractions

摘要

Objective: The purpose of this study was to evaluate the total phenol content and the antioxidant capacity of the hydro-alcoholic bark extract of Piliostigma reticulatum and its ethyl acetate, methanol and aqueous fractions. Materials and Methods: Powdered barks were extracted with ethanol (80%). From the crude extract, 3 fractions were obtained after fractionation by column chromatography with three different solvents (ethyl acetate, methanol and water). The polyphenol content was determined with Folin Denis reagent. Antioxidant activity was performed using DPPH (2, 2-diphenyl-picrylhydrazyl), ABTS (2,2’-azinobis (3-ethylbenzothiazoline 6-sulfonate) and FRAP (ferric reducing antioxidant potential) assays. Results: The total extract had higher polyphenol contents with 12.55 ± 0.12 mg tannic acid equivalent/ g of dried extract (TAE/g). For ethyl acetate, methanol and water fractions, respective polyphenol content of 7.67 ± 0.4 - 9.01 ± 0.05 and 5.56 ± 0.2 mg TAE / g were obtained. The DDPH test had revealed that the methanol fraction was more active (ICsub50/sub: 30.83±0.22 μg/ml), while for ABTS assay the ethyl acetate fraction had shown better activity (ICsub50/sub: 29.08±0.44 μg/ml). For the FRAP test, at all tested concentrations, the methanol fraction revealed highest efficient to reduce ferric ion with percentages of reduction varing from 38 ± 0.73% at 7.81 μg/ml to 93.21 ± 0.24% at 250 μg/ml. Conclusion: These studies showed that the methanol fraction exhibited the best antioxidant activity and that this activity may be related partially to its polyphenols content.