Hypoglycemic activity and histopathological effects of some Kenyan plants traditionally used to manage diabetes mellitus in Eastern province
Ngugi, Mathew Piero
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Diabetes mellitus is a chronic endocrinological disorder characterized by high blood levels of glucose due to insufficient secretion of insulin by the pancreas or improper utilization of insulin by target cells. Diabetes is associated with serious complications and premature death. In Kenya, it is estimated that 190,400 people in the 20-79 age group suffer from diabetes mellitus. There are two types of diabetes mellitus: type I or insulin dependent diabetes mellitus (IDDM) and type II or non-insulin dependent diabetes mellitus (NIDDM). Other forms of diabetes mellitus include secondary diabetes and gestational diabetes. There is an increase in both type I and type II diabetes mellitus but there is a more pronounced increase in type II, which increases at a rate of about 6% annually. The major therapy option in diabetes mellitus is lifestyle management. Besides exercise, weight control and nutrition therapy, oral glucoselowering drugs and insulin injection are the conventional therapies for the disease. Since antiquity, diabetes has been treated with plant medicines. The objective of this study was to bioscreen aqueous extracts of 7 medicinal plants identified using ethnobotanical and pharmacological information gathered from traditional healers for antidiabetic activity and evaluate their safety. Antidiabetic activity was assessed by determining the glucose lowering effect on alloxan induced diabetic mice by intraperitoneally injecting aqueous extracts of these seven plants and toxicity was determined by injecting normal mice with 450mg of the plant extract/kg body weight and histological sections of various organs. The concentration of various trace elements in the seven plant extracts were determined using EDXRF spectrometry and AAS. Of the seven bioscreened plants, only the aqueous leave extracts of Bidens pilosa, and Strychnos henningsii; root bark extracts of Aspilia pluriseta and Catha edulis and stem bark extracts of Erythrina abyssinica showed hypoglycaemic activity. Iron, zinc, lead, magnesium and chromium were present in all the seven plant extracts; copper was present in four plant extracts; nickel and manganese were present in two plant extracts and molybdenum present in only one plant extract. Of the seven plant extracts, one had free antraqunones, two had alkaloids, three had sterols and triterpenes, four had bound anthraquinones, five had saponins, six contained flavones, flavonols and chalcones and all the seven plants contained flavonoids and tannins. Both the trace elements and the phytochemicals accounted for the hypoglycaemic effects and toxicity of the plant extracts. Some of the plants were obviously toxic, others were mildly toxic while others were safe. This study has established that the five bioactive plants can be safely used traditionally for the management of diabetes mellitus. Their use in combination decreases incidences of toxicity.