Traditional medicinal plants have been used for decades in folk medicines in the treatment and management of several ailments and diseases including diabetes, pain, ulcers, cancers, and wounds, among others. This study focused on the phytochemical and antidiabetic activity of the commonly used antidiabetic medicinal species in Kenya. Phytochemical profiling of these species revealed flavonoids and terpenoids as the major chemical classes reported which have been linked with strong biological activities against the aforementioned diseases, among others. However, out of the selected twenty-two species, many of the natural product isolation studies have focused on only a few species, as highlighted in the study. All of the examined crude extracts from thirteen antidiabetic species demonstrated strong antidiabetic activities by inhibiting α-glucosidase and α-amylase among other mechanisms, while nine are yet to be evaluated for their antidiabetic activities. Isolated compounds S-Methylcysteine sulfoxide, quercetin, alliuocide G, 2-(3,4-Dihydroxybenzoyl)-2,4,6-trihydroxy-3 (2H)-benzofuranone, Luteolin-7-O-D-glucopyranoside, quercetin, 1,3,11α-Trihydroxy-9-(3,5,7-trihydroxy-4H-1-benzopyran-7-on-2-yl)-5α-(3,4-dihydroxy-phenyl)-5,6,11-hexahydro-5,6,11-trioxanaphthacene-12-one and [1,3,11α-Trihydroxy-9-(3,5,7-trihydroxy-4H-1-benzopyran-7-on-2-yl)-5α-(3,4-dihydroxy-phenyl)-5,6,11-hexahydro-5,6,11-trioxanaphthacene-12-one]-4'-O-D-gluco-pyranoside from Allium cepa have been found to exhibit significant antidiabetic activities. With the huge number of adults living with diabetes in Kenya and the available treatment methods being expensive yet not so effective, this study highlights alternative remedies by documenting the commonly used antidiabetic medicinal plants. Further, the study supports the antidiabetic use of these plants with the existing pharmacological profiles and highlights research study gaps. Therefore, it is urgent to conduct natural products isolation work on the selected antidiabetic species commonly used in Kenya and evaluate their antidiabetic activities, both in vitro and in vivo, to validate their antidiabetic use and come up with new antidiabetic drugs.
Keywords: Allium cepa; antidiabetic; diabetes; ethnomedicine; phytoconstituents; traditional medicine; α-glucosidase.