Taha Gökmen Ülger^1,, Funda Pınar Çakıroğlu¹

The protective role of Paraoxonase 1 (PON1) enzyme against oxidative stress has not yet been fully elucidated. In some studies, it was suggested that low PON1 activity observed in diabetic cases may be due to increased susceptibility to lipid peroxidation and it is important to identify the changes in PON1 activity level in the as a result of the consumption of foods with antioxidant activity. This study was carried out to determine the changes in PON1 activity value and oxidative stress-related parameters to be resulted by onion which shows an antioxidant activity. It was also aimed to examine the changes to be brought to the functional activity of onion by the heat treatment applied to it. 32 male rats were divided into 4 groups as Group C and Group DC fed with a standard rat diet, Group DLO fed with a diet supplemented with 5% lyophilized onion powder, and Group DFO fed with a diet supplemented with 5% oven-dried onion powder. The rats in the groups were fed for 8 weeks. The rats in Group DC, Group DFO, and Group DLO were induced diabetes by a single dose STZ injection (45 mg/kg). Total Antioxidant Status (TAS) and PON1 activity levels of the Group DLO were significantly higher (p<0.05, p<0.001, respectively) and the Total Oxidant Status (TOS) and Oxidative Stress Index (OSI) values were significantly lower than of the DC group (p>0.05). TAS, TOS, PON1 activity levels and OSI values of Group DC and Group DFO were not significantly different (p>0.05). Group DLO had lower TOS level, higher PON1 activity level and OSI value than Group DFO (p<0.05). Although the findings show that onion may be effective in elevating PON1 activity levels and reducing diabetes-related oxidative stress, heat treatment applied to onion adversely affects these functional effects of it.

paraoxonase, total antioxidant status, total oxidant status, oxidative stress index