oa A Study of antioxidant activity, enzymatic inhibition and in vitro cytotoxicity of selected traditional Sudanese plants with anti-diabetic potential

Introduction: Diabetes mellitus (DM) is a disease with severe complications and major health/economic impacts. It is a leading cause of morbidity and mortality worldwide, with an estimated 346 million adults being affected in year 2011. World Health Organization (WHO) projects indicated that diabetes death will increase by two thirds between 2008 and 2030. The WHO estimated that 80% of the populations of developing countries rely on traditional medicines, mostly plant drugs, for their primary health care needs. Diabetes is an example of a disease that has been treated with plant medicines. Our study evaluated ethanolic and aqueous extracts of selected Sudanese plants that are traditionally used to treat diabetes; these are: Ambrosia maritima, Ammi visnaga, Acacia senegal, Sesamum indicum, Nigella sativa and Foeniculum vulgare. The plants extracts were tested for their glycogen phosphorylase inhibition, toxicity and antioxidant activity. Materials & Methods: Ethanolic and aqueous extracts prepared from leaves of Ambrosia maritime, fruits of Foeniculum vulgare and Ammi visnaga, exudates of Acacia Senegal, and seeds of Sesamum indicum and Nigella sativa were investigated. The antioxidant properties of the extracts were tested using (DPPH) photometric and Iron Chelating Assays. The enzymatic inhibition of glycogen phosphorylase (GP) activity was monitored using multiskan spectrum (Thermo-Scientific). GP activity was measured in the direction of glycogen synthesis by the release of phosphate from glucose-1-phosphate. Brine Shrimp Lethality Test was also used to determine plants toxicity. Results and Discussion: Free radicals are formed in diabetes by glucose oxidation, nonenzymatic glycation of proteins and subsequent oxidative degradation of glycated proteins. Abnormally high levels of free radicals can lead to damage of cellular organelles and enzymes, increased lipid peroxidation and development of insulin resistance. These consequences of oxidative stress can promote the development of complications of diabetes mellitus. In this study all plant extracts with exception of Acacia senegal exhibited significant antioxidant activity in DPPH free radical scavenging assay. This may support the traditional usage of these plants to improve complications that caused by diabetes mellitus. Nigella sativa aqueous extract showed no toxicity on Brine shrimp Lethality Test, while its ethanolic extract was toxic. All other extracts are toxic and ethanolic extracts of Foeniculum vulgare and Ammi visnaga exhibit the highest toxicity. Results of this study did not show any significant inhibition of glycogen phosphorylase, but extracts of these plants may act on one of other enzymatic reactions that involved in carbohydrate metabolism and improved glucose homeostasis. Conclusion and Recommondation: Changes in oxidative stress and effects of antioxidants in diabetes management should be considered, and hopefully, further research into the pathophysiology of oxidative stress and the role of antioxidant therapy will lead to appropriately-designed clinical trials in which the promise of antioxidant therapy will be realized. Extraction processes and usage doses should be monitored. Further work is underway to test the plant extracts on diabetes-induced mice. Key words: Diabetes mellitus, medicinal plants, antioxidant activity, glycogen phosphorylase, brine shrimp