Comparative Phytochemical and Antioxidant Analysis of the Leaf Extracts of Two Nigerian Medicinal Plants

Abstract

Bridelia ferruginea (Benth., Euphorbiaceae), prominently found in Savannah regions, is commonly used as an ethnomedicine for the treatment of several ailments in many parts of Africa. Piliostigma thonningii (Schum., Fabaceae) is used for various medicinal purposes in African countries with some pharmacological activities established from the crude extracts including antibacterial, antihelminthic, antiinflammatory and antilipidemic activities. In the present study, crude methanolic extract and fractions of B. ferruginea and P. thonningii were examined for their phytochemical constituents and antioxidant activity using standard protocols. Qualitative phytochemical screening of B. ferruginea crude extract revealed the presence of tannins, saponins, phlobatanins, flavonoids, steroids, alkaloids, glycosides, phenols and resins while it tested negative for triterpenoids, carbohydrates, terpenoids and anthraquinones; the quantitative phytochemical analysis showed that it contained 1.5% saponins, 5.3% flavonoids, 1.2% alkaloids and 0.9% phenols. P. thonningii crude extract tested positive for saponins, flavonoids, terpenoids, steroids, alkaloids, and phenols while tannins, phlobatanins, glycosides, triterpenoids, carbohydrates, resins and anthraquinones were absent. It contains 3.2% saponins, 1.6% flavonoids, 1.8% alkaloids, and 0.7% phenols. The concentration of the crude extract required for 50% inhibition of DPPH radical scavenging effect (IC₅₀) is 0.018 and 0.020 mg/ml for B. ferruginea and P. thonningii, respectively, compared to 0.015 mg/ml for vitamin C as a standard antioxidant. Both extracts showed potent inhibition of DPPH radical scavenging activity comparable to that of the Vitamin C standard and would be valuable sources of antioxidant compounds.