Antioxidant Properties and α-amylase Inhibition of Terminalia superba, Albizia sp., Cola nitida, Cola odorata and Harungana madagascarensis Used in the Management of Diabetes in Cameroon

Abstract

Aqueous, ethanolic, hydroethanolic and methanolic extracts of Albizia sp., Cola nitida, Terminalia superba (T. superba), Cola odorata and Harungana madagascarensis were screened for phytochemical constituents. The evaluations of the antioxidant potential and α-amylase inhibitory activity of these extracts were also carried out. Tests for tannins and phenols were positive in all extracts, with the highest total phenol content observed in the ethanolic extract of T. superba. This extract, as well as the aqueous and hydroethanolic extracts of the same plant had the highest antioxidant properties as determined by the ferric reducing antioxidant power (FRAP) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) methods. For all the plants tested, at least one extract inhibited the activity of α-amylase. The most effective was the hydroethanolic extract of T. superba. The presence of active phytochemical substances with antioxidant properties may account for the above mentioned properties, and provide substantial basis for the use of these plants in ethno-medicine for the treatment of diabetes.