Diabetes mellitus is one of the major health problems in Africa. The conventional oral synthetic antidiabetic drugs available to manage the disease are costly and not readily affordable to the majority of the affected population. Interestingly, the continent is endowed with a tremendous number of medicinal plants that have been explored for their folkloric treatment of diabetes mellitus. Scientific investigations have validated the antidiabetic potentials of a number of these medicinal plants but there is no repository with information on these scientifically investigated plants as a guide for future research. In this review article, all of the in vivo antidiabetic studies conducted between January 2000 and July 2013 on African plants are systematically compiled with a closer look at some relevant plants from the continentʼs subregions. Plants of the Asteraceae and Lamiaceae families are the most investigated, and West Africa has the highest number of investigated plants. Although promising results were reported in many cases, unfortunately, only a few studies reported the partial characterization of bioactive principles and/or mechanisms of action. It is hoped that government agencies, pharmaceutical industries, and the scientific community will have a look at some of these plants for future research and, if possible, subsequent commercialization.

This study evaluated the in vitro antioxidative activity of Khaya senegalensis extracts and inhibitory effects of some solvent fractions on α-glucosidase and α-amylase activities. The stem bark, root and leaf samples of the plant were sequentially extracted with ethyl acetate, ethanol and water and then tested for antioxidative activity. Our findings revealed that the ethanolic extract of the root had the highest antioxidative activity. Solvent-solvent fractionation of the root ethanolic extract yielded a butanol fraction that showed higher antioxidative activity than other fractions. Furthermore, the butanol fraction had significantly higher (p < 0.05) α-glucosidase and α-amylase inhibitory activities with IC ₅₀ values of 2.89 ± 0.46 and 97.51 ± 5.72 μg mL ^-1 , respectively. Enzyme kinetic studies indicated that the butanol fraction is a non-competitive inhibitor for α-glucosidase with an inhibition binding constant K _i of 1.30 μg mL ^-1 and a competitive inhibitor of α-amylase with a K _i of 7.50 μg mL ^-1 . GC-MS analysis revealed that the butanol fraction contained two chromones, p-anilinophenol and 3-ethyl-5-(3- ethyl-(3H)-benzothiazol-2-ylidene)-2-(p-tolylvinylamino)- 4-thiazolidinone. Data obtained in the study suggest that the butanol fraction derived from the ethanolic extract of K. senegalensis root possessed excellent antioxidative as well as α-glucosidase and a-amylase inhibitory activities while chromones and/or p-anilinophenol could be the main bioactive compounds responsible for the observed activities.