Isolation of pentacyclic triterpene, phenolic content and antioxidant activity of root bark of Irvingia gabonesis Baill. (Irvingiaceae)

The aim of this study was to investigate the phytochemical constituents and antioxidant potentials of the ethanol extract and fractions of Irvingia gabonensis root bark in order to establish the scientific basis and rationale for its folkloric use. The powdered root bark of I. gabonensis was macerated with 70% ethanol and then partitioned with different solvents based on their polarity to afford 4 fractions. The extract and fractions were subjected to phytochemical analysis. The in vitro antioxidant activity was evaluated using DPPH assay. The quantitative phytochemical determination showed that ethyl acetate fraction of I. gabonensis root bark (EFIGR) had the highest content of tannins (154.44 mg/GAE g), phenol (106.26 mg/GAE g and flavonoid (76.07 mg/QE g). The in vitro antioxidant activity of the extract and the fractions had IC50 values of 76.0±0.03, 27.0± 0.05, 39.0±0.07 and 28.0±0.10 μg/mL for Ethanol extract, EFIGR, Butanol fraction and Aqueous fraction respectively while the standard had 29.0±0.03 μg/mL.Further fractionation of EFIGR led to the isolation of hederagenin which was characterized using 1D-NMR and mass spectrometric data. The present study revealed that root bark of I. gabonensis is a potential sourceof natural antioxidant which justified its uses in the traditional medicine.