Plant-Derived Antidiabetic Compounds Obtained From African Medicinal Plants: A Short Review

The continent of Africa is endowed with the richest biodiversity in the world, with an abundance of plants used in traditional treatment of various diseases such as diabetes mellitus (DM). In the last few decades, scientists have investigated the antidiabetic potential of a number of African medicinal plants, and some bioactive compounds were isolated and screened as well. In our previous study, a total number of 185 plant species from 75 families were investigated for antidiabetic actions in Africa between 2000 and 2013. But the study mainly focused on plant extracts and/or fractions. The compounds reported in the study were detected in the extracts and/or fractions that showed antidiabetic actions, with no report on the antidiabetic activities of the bioactive compounds. Additionally, no isolated compound from the continent was reported in a recent study by that highlighted antidiabetic compounds isolated between 2005 and 2010. But there is no repository of information on these investigated bioactive compounds as a guide for future research. This chapter documents all bioactive compounds from African medicinal plants that have been isolated and investigated for possible antidiabetic effect along with an attempt to highlight the structure-activity relationships (SAR) of the isolated bioactive compounds. A total of 53 compounds isolated from African medicinal plants have been investigated as possible antidiabetic agents, which include three phenolic compounds from marine algae Ecklonia maxima (Osbeck) Papenfuss. Moreover, 45 bioactive compounds showed variable antidiabetic potentials, when eight compounds were inactive in the models used in the reported studies. Kolaviron showed promising antidiabetic action when epicatechin, dibenzo (1,4) dioxine-2,4,7,9-tetraol, and brevipsidone D are potential hits and require further work to validate their potential antidiabetic activities. Based on the SAR of the isolated compounds, the positions and interactions of some chemical groups such as hydroxyl, methoxy, prenyl, carboxylic, and catechol moieties in the bioactive compounds greatly affect their antidiabetic actions. In conclusion, more bioassay-guided isolations of African natural products need to be conducted to find promising antidiabetic leads that could overcome the adverse effects of the currently available synthetic drugs.