In vitro antioxidant activity and phenolic contents of different fractions of ethanolic extract from Khaya senegalensis A. Juss. (Meliaceae) stem barks

Khaya senegalensis A. Juss (Meliaceae) is a medicinal plant used in folk medicine of Burkina Faso. Its stem barks are used to treat several diseases such as inflammation, arthritis, infections, ulcer, malaria, fever and dermatosis. The antioxidant activity of aqueous ethanol extract and fractions of Khaya senegalensis stem bark was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH•), 2,2'-azino-bis (ABTS•+), ferric reducing antioxidant power (FRAP) and lipidic peroxidation methods. Total phenolic, tannins, flavonoids and flavonol contents of extract and fractions were determined. Butanol fraction had the highest value with IC50 =1.76 ± 0.19 µg ml-1 (ARP = 0.56) with DPPH• assay, however n-hexan fraction showed the highest capacity to scavenge ABTS•+; FRAP values varied from 13.04 ± 0.25 to 13.60 ± 0.09 mmol Trolox Equivalent per gram (mmol TE g-1) of extract or fraction. Ethyl acetate fraction presented the best activity (70.30 ± 0.40%, 100 µg ml-1) using lipid peroxidation inhibition method. Aqueous fraction contained the highest of total phenolics and tannins contents with, respectively 3.68 ± 0.11 and 2.65 ± 0.18 g TAE/100 g of dry weight (dw) of plant material. Aqueous fraction also showed the highest of total flavonoids (0.04 ± 0.01 g QE/100 g dw) and flavonol (0.10 ± 0.01 g QE/100 g dw) contents. K. senegalensis possesses a potential antioxidant effect and contains phenolic compounds. These results provide scientific evidence that validates the use of K. senegalensis in traditional medicine. Key words: Khaya senegalensis, antioxidant, phenolic, flavonoids, tannins