Diabetes is a problem in Kenya and many herbal preparations are being used to treat it. This study aimed at documenting the plants that are used for the treatment of diabetes mellitus in Machakos County in Kenya, the three most commonly used plants were subjected to phytochemical screening and efficacy evaluation as well as effects on biochemical parameters, liver and kidney histology. The ethnobotanical information was collected through questionnaires, focus group discussions, collection and identification of the plant specimens. Phytochemical screening was done using standard techniques. The most commonly employed species Zanthoxylum chalybeum, Ficus sycomorus and Ximenia americana were selected for phytochemical analysis and efficacy and safety evaluation. Antidiabetic efficacy was determined using a rat model of diabetes mellitus. The efficacy study used 75 adult male Wistar rats. Aqueous stem bark extracts of the three plants were administered to diabetic rats after induction of diabetes via single streptozotocin injection (45mg/kg bwt intraperitoneally). Development of hyperglycemia was assessed by measuring blood glucose three days post induction and comparing these with normal controls. The efficacy of the plant extracts was also compared against Glibenclamide, a conventional diabetes drug. A total of nineteen plant species distributed across 13 families were identified as being used to manage diabetes mellitus. The secondary metabolites in Zanthoxylum chalybeum, Ficus sycomorus and Ximenia americana were flavonoids, terpenoids, tannins and glycosides. Zanthoxylum chalybeum also contained alkaloids and saponins. All three plants investigated exhibited significant antidiabetic activity compared to the untreated diabetic controls (P<0.05). Diabetic rats exhibited elevated fasting blood glucose levels, decreased body weight, and increased water and food intake. Zanthoxylum chalybeum stem bark extract decreased fasting blood glucose in diabetic rats at three dose levels (10mg, 100mg and 1000mg). There was no significant difference between the extract fed diabetic rats and the normal controls (P<0.05). Ficus sycomorus stem bark extract significantly reduced glucose levels in diabetic rats (P<0.05) at doses of 100mg and 10mg/kg bwt compared to untreated diabetic rats. Ximenia americana stem bark extract at the three dose levels employed, reduced blood glucose to levels that were not statistically significant (P<0.05) compared to the Glibenclamide group. Additionally at 100mg and 10mg/kg bwt, blood glucose levels were significantly reduced compared to the untreated diabetic group. These observations suggest that the aqueous stem bark extracts of Z. chalybeum, F. sycomorus and X. americana possess significant antihyperglycemic activity. The phytochemical composition of the plants may account for the antidiabetic activity observed, as well as the differences in efficacy between the plants. There was no difference in the biochemical parameters in the experimental groups thus the plants can be deemed safe at the dosages used. This study thus validates the traditional use of the three plants for the management of diabetes mellitus in the study area. The study recommends further studies to determine the most efficacious doses of the plant extracts. A study of the remaining sixteen plants should also be carried out to determine their efficacy in the management of diabetes.

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