The onset of diabetic complications is attributed to sustained hyperglycemia which triggers the generation of free radicals and oxidative-related damage in the retina, renal glomerulus and peripheral nerves. Recent studies report that intense glycaemic control by the subcutaneous administration of insulin cannot completely restore the balance between reactive oxygen species and antioxidants. Preliminary studies in our laboratory indicate that transdermally delivered Syzygium aromaticum-derived oleanolic acid (OA) has the ability to lower blood glucose in experimental diabetes mellitus due to the sustained release of the triterpene. However, no work has been done to determine the effects of OA on reactive oxygen species (ROS). Research has indicated that some bioactive compounds such as flavonoids and tannins have antioxidant properties. Accordingly, this study was designed to investigate and evaluate the effects of S. aromaticum-derived OA on ROS levels. The acute effects of OA were evaluated on malondialdehyde (MDA) and glutathione (GSH) concentrations in STZ-induced diabetic rats following a glucose load after an 18-h fast. Rats administered pectin-free OA or transdermally delivered insulin acted as untreated and treated positive controls, respectively, while non-diabetic rats served as absolute controls. The transdermal patches were applied for 6 h, thereafter the animals were sacrificed. The heart, liver and kidney were collected for ROS biomarkers (MDA) and antioxidants (GSH) analysis. MDA levels were significantly reduced in the heart (233.0±0.1 vs 47.0±0.1 nmol/l) and liver (233.0±0.1 vs 130.0±0.1 nmol/l). Interestingly, GSH levels were also significantly increased in the heart (196.0±0.4 vs 313.0±0.5 nmol/l). These results suggest that S. aromaticum-derived OA is potentially effective in ameliorating the oxidative stress observed in diabetes mellitus in the heart. It can therefore, be concluded that OA is a potential drug for diabetes mellitus that would not only lower blood glucose but also can avert complications that arise due to oxidative stress.
Declaration of funding: This study was partly funded by the NRF South Africa and the University of KwaZulu-Natal, Research Division.