Objective: This study aims to evaluate the effects of onion (Allium cepa L.) against hyperglycaemia and dyslipidemia and determine possible changes in these effects due to different heat treatments applied to onion.
Materials and methods: 32 male Wistar-albino rats were divided into 4 groups as follows: the groups C and DC were fed with standard rat diet; the DLO group was fed with rat diet including 5% onion powder dried at -76°C in a lyophilizator, and the DFO group was fed with rat diet including 5% onion powder dried at 80°C in a furnace. Diabetes was induced in DC, DLO and DFO groups by injection of streptozotocin (45 mg/kg).
Results: A decreasing tendency was observed in fasting blood glucose (FBG) values of DLO group during the experiment period and it was found that the 6th and 8th weeks values were significantly lower than the 1st and 2nd weeks values (p<0.05). On the other hand, no statistical difference was observed in the FBG values measured at different weeks in the DFO group. Significant differences were also observed among the groups in terms of plasma lipid values. DLO group was determined to have lower levels of triglyceride (p<0.001), LDL cholesterol and total cholesterol and higher levels of HDL cholesterol (p<0.05 for all cases) compared to the DC group whereas no significant difference in these values was found between the DFO and DC groups.
Conclusion: Lyophilized onion powder may be protective against hyperglycaemia and dyslipidemia arising from diabetes. However, the heat treatments applied to onion affect this protective role negatively.
Keywords: Allium cepa; Dyslipidemia; Herbal medicine; Hyperglycemia; Streptozocin.