Phytochemical and antioxidant evaluation of cassia sieberiana D.C. stem bark extracts

Abstract

Cassia sieberiana D.C. belongs to the Fabaceae family and it is used ethnomedically in the management of cancer, diabetes and other diseases. There is a growing concern about the scourge of diseases caused by excessive free radicals in the body and lack of standardization of medicinal herbal products. Therefore, this research is aimed at evaluating the phytochemical and free radical scavenging activities of the plant extracts with the view to identify the chemical constituents and antioxidant properties of the extracts. The powdered stem bark was evaluated for its pharmacognostic profiles and then extracted successively with the aid of Soxhlet extractor using n-hexane, ethyl acetate and methanol. The extracts obtained were concentrated using rotary evaporator and the percentage yields of the extracts were determined. The extracts were screened for their phytochemical constituents using standard protocols. The thin layer chromatography (TLC) profiles of the resulting extracts were determined using suitable solvent systems and the retention factor (Rf) values of separated spots of compounds were calculated. The total phenolic content of the ethyl acetate and methanol extracts were measured using Folin-Ciocalteu reagent and gallic acid was used as standard. The antioxidant (free radical scavenging) activity of the extracts were measured using DPPH (2, 2-diphenyl-1- picryl hydrazyl) and ascorbic acid was used as standard. The results were expressed in terms of percentage inhibition. The percentage yields of the extracts were: 0.52 %, 6.58 % and 10.52 % respectively for n-hexane, ethyl acetate and methanol. The preliminary phytochemical screening of the extracts revealed the presence of tannins, cardiac glycosides, saponins, flavonoids and triterpenoid/steroids. Also, the total phenolic contents were found to 7.64 mg and 2.97 mg gallic acid equivalents for ethyl acetate and methanolic extract respectively. The free radical scavenging activity of the extracts revealed higher activity in the ethyl acetate extract. The results indicated that the extracts contain phenolic compounds which may be responsible for the antioxidant activity.