Analysis of phenolic compounds and evaluation of antioxidant activity of aqueous and hydromethanolic extracts of the leaves and bark of Alstonia boonei De wild

Abstract

Oxidative stress is one of the precursors of a number of diseases. It can be eliminated by an external supply of antioxidants, which are sometimes difficult to obtain. We assessed the antioxidant power of extracts of Alstonia boonei De Wild using the DPPH method, and determined and characterised the phenolic compounds using UV/visible spectrophotometry and TLC. The aqueous and hydromethanolic extracts of the plant contain polyphenols with contents varying from 1163.87 ± 5.12 to 2577.50 ± 7.06 mg GAE/100 g DM, flavonoids: 142.72 ± 8.19 to 1472.10 ± 5.34 mg QE/100 g DM, condensed tannins: 4.507 ± 0.041 to 161.963 ± 0.35 mg CE/100 g DM and hydrolysable tannins: 22.07 ± 1.60 to 305.95 ± 0.91 mg GAE/100 g DM. TLC yielded compounds that could be flavonoid glycosides and proanthocyanidins. The antioxidant activity of these extracts gave 50% CIs ranging from 7.53 to 19.15 µg/mL. Extracts of the leaves and bark of Alstonia boonei De Wild are rich in phenolic compounds and have good antioxidant activity.