Atıf Detayı

Cola caricifolia (G.Don) K. Schum and Crotalaria retusa L. are important plants in African traditional medicine used against a plethora of human ailments. In this study, phytochemical characterization and enzyme inhibitory assays were performed to assess the potential usefulness of C. caricifolia and C. retusa leaves extracts as source of bioactive constituents for potential industrial applications. The flavonoid content of C. caricifolia (22.27 mg rutin equivalent (RE)/g) was significantly higher (p<0.05) than C. retusa (12.45 mg RE/g) methanol extract. Inhibitory activity against acetylcholinesterase, butyrylcholinesterase, and tyrosinase were evaluated for all the extracts (ethyl acetate, methanol, and water), whereby the best activity recorded for the methanol extracts. Additionally, the methanol extracts of C. caricifolia and C. retusa showed significant antioxidant activity in the phosphomolybdenum, metal chelating, reducing power, and radical scavenging assays. Flavonoid glycosides and caffeoyl derivatives were the most abundant constituents in C. caricifolia. Crotalaria retusa contained several flavonoid glycosides with structures not described previously. One new compound, kaempferol-6-C-β-glucopyranoside-3-O-β-glucopyranosil-6-O-caffeoyl ester has been elucidated using spectroscopic method in the current study. Derivatives present in minor amount were tentatively identified as kaempferol glycosides. Overall phytochemical investigations allowed the identification of flavonoid O and C glycosides, caffeic acid derivatives, and phytosterols from both plant extracts while pyrrolizidine alkaloids were identified in C. retusa. Structural characteristics of the new isolated compounds along with the most abundant constituents of the two extracts were elucidated allowing the observation of some structural moieties related to the observed activity. These observations highlighted the potential use of these plants as a source of multi-directional biological agents that could lead to bioproducts development.