Antihyperglycemic Actions of Eucalyptus globulus (Eucalyptus) are Associated with Pancreatic and Extra-Pancreatic Effects in Mice

Manuscript received 8 April 1998. Initial reviews completed 5 June 1998. Revision accepted 11 August 1998.

School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, BT52 1SA, UK

Eucalyptus globulus (eucalyptus) is used as a traditional treatment for diabetes. In this study, incorporation of eucalyptus in the diet (62.5 g/kg) and drinking water (2.5 g/L) reduced the hyperglycemia and associated weight loss of streptozotocin-treated mice. An aqueous extract of eucalyptus (AEE) (0.5 g/L) enhanced 2-deoxy-glucose transport by 50%, glucose oxidation by 60% and incorporation of glucose into glycogen by 90% in mouse abdominal muscle. In acute, 20 min incubations, 0.25-0.5 g AEE/L evoked a stepwise 70-160% enhancement of insulin secretion from the clonal pancreatic -cell line (BRIN-BD11). The stimulatory effect of 0.5 g/L AEE was unaltered by the presence of 400 µmol diazoxide/L and prior exposure to AEE did not alter subsequent insulin secretory response to L-alanine, thereby negating adetrimental effect on cell viability. The effect of AEE was not potentiated by glucose or demonstrable in cells exposed to a depolarizing concentration of KCl. Further study of the insulin-releasing effects of AEE revealed the activity to be heat stable, acetone insoluble, stable to acid, but abolished by exposure to alkali. Sequential extraction with solvents revealed activity in both methanol and water fractions, indicating the presence of more than one biologically active extract constituent. These data indicate that Eucalyptus globulus represents an effective antihyperglycemic dietary adjunct for the treatment of diabetes and a potential source for discovery of new orally active agent(s) for future therapy.

The Journal of Nutrition Vol. 128 No. 12 December 1998, pp. 2319-2323
Copyright ©1998 by the American Society for Nutritional Sciences

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