Antioxidant Activity and a New Ursane-type Triterpene from Vitellaria paradoxa (Sapotaceae) Stem Barks

Abstract

Aims: The aim of the present study was to evaluate the total phenolics and flavonoids content of stem barks of Vitellaria paradoxa C. F. Gaertn., and identify its main chemical constituents. Methodology: V. paradoxa stem barks were extracted by maceration with methanol. Preliminary phytochemical screening was performed on the crude methanol extract (CME). Besides, total polyphenols contents (TPC) and total flavonoids contents (TFC) contents were also evaluated using the Folin-Ciocalteu method and complexation with aluminum chloride respectively. The antioxidant activity was evaluated by DPPH (2.2-diphenyl-1-picrylhydrazyl) and FIC (ferrous ion chelating) assays. Chromatographic isolation of the crude methanol extract (CME) followed by the spectroscopic identification of the isolated compounds was performed adopting 1D NMR and MS techniques. Results: All the compounds tested were found to be present in the CME of V. paradoxa stem barks. The extract was found to be rich in phenolics (18.48 ± 1.43 mgGAE.g-1) and flavonoids (3.98 ± 0.44 mgGAE.g-1). The CME showed high antioxidant activity as DPPH free radical scavenging and a low FIC activity. A new ursane type-triterpenoid named vitellaric acid (4) along with four known compounds (+)-catechin (1), (-)-epicatechin (2), betulinic acid (3a), and bassic acid (3b) were isolated from CME. Conclusion: The results of preliminary phytochemical screening of the leaf extracts revealed the presence of phytochemicals which could be used as medical regimens. The study provides scientific evidence for the use of V. paradoxa stem barks for the treatment of diseases mainly those associated with oxidative stress due to reactive oxygen species. Results yield a new addition to the chemical literature of V. paradoxa, in addition it increases the importance of NMR and MS techniques in structure elucidation.