In our experiments 30 hypoglycaemic medicinal plants (known and less known) have been selected for thorough studies from indigenous folk medicines, Ayurvedic, Unani and Siddha systems of medicines. In all the experiments with different herbal samples (vacuum dried 95% ethanolic extracts), definite blood glucose lowering effect within 2 weeks have been confirmed in alloxan diabetic albino rats. Blood glucose values are brought down close to normal fasting level using herbal samples at a dose of 250 mg/kg once, twice or thrice daily, as needed. While evaluating comparative hypoglycaemic activity of the experimental herbal samples, significant blood glucose lowering activities are observed in decreasing order in the following 24 samples-Coccinia indica, Tragia involucrata, G. sylvestre, Pterocarpus marsupium, T. foenum-graecum, Moringa oleifera, Eugenia jambolana, Tinospora cordifolia, Swertia chirayita, Momordica charantia, Ficus glomerata, Ficus benghalensis, Vinca rosea, Premna integrifolia, Mucuna prurita, Terminalia bellirica, Sesbenia aegyptiaca, Azadirachta indica, Dendrocalamus hamiltonii, Zingiber officinale, Aegle marmelos, Cinnamomum tamala, Trichosanthes cucumerina and Ocimum sanctum. Present studies besides confirming hypoglycaemic activities of the experimental herbal samples, help identify more potent indigenous hypoglycaemic herbs (in crude ethanolic extract) from the comparative study of the reported experimental results.

To unravel the possible mechanism of glucose lowering activity, effects of ten different plant extracts in the regulation of serum cortisol and glucose concentrations were evaluated in male mice. While the extracts of Inula racemosa, Boerhaavia diffusa and Ocimum sanctum decreased the serum concentration of both cortisol and glucose, Aegle marmelos, Azadirachta indica and Gymnema sylvestre extracts could exhibit hypoglycaemic activity without altering the serum cortisol concentration. It appears that the hypoglycaemic effects of former three plant extracts are mediated through their cortisol inhibiting potency, whereas the mechanism for other plant extracts could be different. Lipid-peroxidation was not enhanced by any of the plant extracts (some were in fact, antiperoxidative in nature). As I. racemosa, B. diffusa and O. sanctum exhibited antiperoxidative, hypoglycaemic and cortisol lowering activities, it is suggested that these three plant extracts may potentially regulate corticosteroid induced diabetes mellitus.

Effect of Dianex, a herbal formulation on experimentally induced diabetes mellitus

Possible mechanism of antihyperglycemic effect of Azadirachta indica leaf extract. Part IV

1. Effect of epinephrine on the increment index calculated from intravenous glucose tolerance tests and on hepatic glycogen before and after A. indica leaf extract treatment was studied in normal and streptozotocin-induced diabetic rabbits. 2. A. indica leaf extract, in itself, was found to have no action on peripheral utilization of glucose or on hepatic glycogen. 3. The reduction in peripheral utilization of glucose and glycogenolytic effect due to epinephrine action was blocked by A. indica leaf extract, however, almost completely in diabetic rabbits and to a certain extent in normal ones. 4. The results are discussed.

To study the comparison of blood sugar lowering activity of four medicinal plants Azadirachta indica, Gymnema sylvestre, Catharanthus roseus and Ocimum sanctum

A comparison of blood sugar lowering activity of four important medicinal plants (Azadirachta indica, Gymnema sylvestre, Catharanthus roseus and Ocimum sanctum) were carried out against normal and streptozotocin-induced diabetic rat models. The plant extracts decreased the blood sugar level in varying degrees. Blood sugar lowering unit (BLU) of activity of each leaf extract and tolbutamide was calculated by ED50 values. Statistical analysis revealed significant (P < 0.05) variation among the treatments as well as doses with regard to their blood sugar lowering capacity. A. indica leaf extract was found to have the most potent blood sugar-lowering activity followed by C. roseus, G. sylvestre and O. sanctum.

To investigate Diamed for its possible antihyperglycaemic action in rats with alloxan-induced experimental diabetes

Department of Biochemistry, Annamalai University, Tamil Nadu, India. paribala@sancharnet.in

Diamed is a herbal formulation composed of the aqueous extracts of three medicinal plants (Azardirachta indica, Cassia auriculata and Momordica charantia). We have investigated Diamed for its possible antihyperglycaemic action in rats with alloxan-induced experimental diabetes. Oral administration of Diamed (1.39 (0.25 g), 1.67 (0.30 g) or 1.94 (0.35 g) mL kg(-1)) for 30 days resulted in a significant reduction in blood glucose, glycosylated haemoglobin, and an increase in plasma insulin and total haemoglobin. The effect was highly significant after administration of the 1.94 mL (0.35 g) g(-1) body weight dose. Diamed also prevented a decrease in body weight. An oral glucose tolerance test was performed in experimental diabetic rats in which there was a significant improvement in glucose tolerance in the animals treated with Diamed. The effect was compared with 600 microg kg(-1) glibenclamide. The results showed that Diamed had antihyperglycaemic action in experimental diabetes in rats.