The antidiabetic properties of four plants grown in India and KwaZulu-Natal, South Africa, suitable for diabetic management

Abstract
Over the years, it has been suggested that various medicinal plants have anti-glycaemic properties which could help in the management of diabetes mellitus, a complex metabolic disorder. We aimed to evaluate the nutritional content (proximate and mineral) of four ayurvedic plants: Abelmoschus esculentus (L.) Moench, Momordica charantia L, Moringa oleifera Lam, Solanum melongena L. to identify nutritional differences between the Indian and South African varieties. An assessment of the anti-glycaemic activity of the aqueous and boiled extracts of the samples from South Africa was carried out by monitoring glucose, triglyceride and cholesterol levels as well as body weight in alloxan-induced diabetic rats and their control group over a 15 day period. Ninety-two Sprague-Dawley rats were separated into 7 groups (see table 3.3). Diabetes was induced in 48 rats by a single intraperitoneal injection of alloxan, 150mg/kg body weight. The apparent mechanism of anti-glycaemia was also investigated using the inverted intestine test, the glycogen content within the liver, the activity of Na/K ATPase and by assessing glucokinase and hexokinase activity by analysing liver and gastrocnemius muscle tissue. Results revealed that all four plants were reported to have protein, fats, glucose and starch, with the South African varieties showing higher protein content than the Indian varieties. According to mineral analysis by the varian inductively coupled plasma (ICP), all the four plants are rich in minerals. The in vivo studies revealed that all the plant extracts showed hypoglycaemic effects within the two week study period except the A.esculentus boiled extract. Preliminary experiments demonstrated that aqueous extracts of M.charantia and A.esculentus had maximum antidiabetic potential compared to the other plant extracts. The aqueous extract of M.charantia and A.esculentus fruits, at a dose of 300 mg/kg body weight, showed a statistically significant lowering of the glucose level of alloxan induced diabetic rats compared to the control group from 22.78 mmol/L to 8.1 mmol/L and 22.2 mmol/L to13.3 mmol/L respectively, after 15 days of treatment. The enteral use of M.charantia and A.esculentus extract resulted in an increase in body weight in diabetic rats and a reduction in body weight in the diabetic control rats. M.charantia and A.esculentus extracts lowered the entry of glucose into the intestine. Treatment with M.charantia and A.esculentus increased the glycogen content by 47.3% (M.charantia aqueous) 59.2% (M.charantia boiled), 55% (A.esculentus aqueous) compared to the diabetic control group. The evaluation of Na+/K+-ATPase activity revealed a more statistically significant inhibitory activity (25%) with the use of A.esculentus compared to M.charantia (12.5%). Hexokinase and glucokinase activity was reduced in the diabetic control rats as compared to the non-diabetic rats, with respective percentage decreases in activity of 66.7% and 83.3%. Treatment with Momordica charantia and Abelmoschus esculentus significantly increases the activity of these enzymes (P<0.001 as compared to diabetic controls). On the other hand, there was no change in glucokinase activity in non-diabetic treated groups. Histological analysis of diabetic control livers showed slight degenerative changes, which was within normal histological limits. Analysis of groups treated with extract showed mild diffuse sinusoidal congestion with mild hydropic degeneration which was within normal histological limits. Gastrocnemius muscle analysis of diabetic control, diabetic and non-diabetic treated groups appeared within normal histological limits. This revealed that the plant extracts of M.charantia and A.esculentus were non-toxic and thus advisable for safe consumption. The inclusion of these vegetables on a regular basis in the daily diet, together with medication and exercise would improve general health and blood glucose control in diabetic patients.
Description
A dissertation submitted to the Faculty of Science and Agriculture in fulfilment of the requirements for the degree of Doctor of Philosophy in Biochemistry in the Department of Biochemistry and Microbiology at the University of Zululand, South Africa, 2015
Keywords
antidiabetic ailments --herbal treatments --plants --diabetes
Citation