Abstract
The current study aims at exploring enzyme inhibition of four species of medicinal herbs, namely Senna bicapsularis, Thevetia peruviana, Nerium oleander and Vinca major. Plant selection was done on the basis of their therapeutic uses by local practitioners. The crude methanolic extracts of these plants were tested for their alpha-glycosidase and urease enzyme inhibition potential. The observed urease inhibitory potential for the crude extract of S. bicapsularis, T. peruviana and N. oleander were 8.3 +/- 0.33 mu g, 6.98 +/- 0.98 mu g and 9.56 +/- 1.43 mu g, respectively while the V. major did not show any inhibition. In addition, the IC50 value for Thiourea was 22.3 +/- 1.14 mu g. The crude extracts of S. bicapsularis, T. peruviana, N. oleander, V. major were shown to inhibit alpha-glycosidase activity with an IC50 value of 630.3 +/- 0.03 mu g, 700.7 +/- 2.43 mu g, 430.4 +/- 3.97 mu g, and the standard (acarbose) 880 +/- 1.03 mu M, respectively. Based on the TLC profile, the extract of S. bicapsularis was subjected to column chromatography and the major component named rhein (1) was identified. Compound 1 exhibited excellent urease and alpha-glycosidase inhibitory activity with an IC50 value of 7.4 +/- 0.32 and 622.3 +/- 1.03 mu M, respectively.