Evaluation of the antioxidant potentials of extract and fractions of Vitex doniana fruit and identification of the bioactive metabolites using HPLC-DAD-MS analysis

Isoflavones and flavonoids in general found in fruits and vegetable act as natural antioxidants. This study was aimed at screening the isoflavone-rich fractions of Vitex doniana fruit extract for antioxidant activity using in vitro and in vivo models. The ethyl acetate and butanol fractions were screened for in vitro antioxidant activity by DPPH free radical scavenging and FRAP (Fe3+ Reducing Antioxidant Power) assays using ascorbic acid as standard. In vivo antioxidant activity was also tested against carbon tetrachloride-induced toxicity in mice using carbon tetrachloride (4 mL/kg) and silymarin (100 mg/kg) as standard. The ethyl acetate fraction and butanol Vacuum Liquid Chromatography (VLC) sub-fractions were subjected to High Performance Liquid Chromatography–Diode Array Detector (HPLC-DAD) and Liquid Chromatography-Mass Spectrometry (LC-MS) analyses. The ethyl acetate and butanol fractions inhibited DPPH radicals with an IC50 of 897 µg/mL and 2809.38 µg/mL respectively. Both fractions also showed mild FRAP result with EC50 of 1401 µg/mL and 7051 µg/mL respectively. The fractions produced significant decrease (P < 0.05) in ALP levels only while ethyl acetate fraction caused a significant reduction in the value of only malondialdehyde. Both fractions also increased levels of superoxide dismutase (SOD). HPLC-DAD analysis led to the detection of cinnamic acid, protocatechuic acid and two isoflavones daidzein and genistein. Further LC-MS analysis confirmed the presence of the isoflavones tectorigenin, 5-O-methylgenistein, and 5-O-methyltectorigenin, among other flavonoids, peonidin, 5-methylpeonidin, methylmalvidin and kaempferol-3-O-(2''galloyl)-glucopyranoside. The detected isoflavones and other flavonoids may contribute to the observed mild in vitro and good in vivo antioxidant activity of V. doniana fruit extract and fractions.