Background and Aims: Flavonoids as polyphenolic naturally occurring compounds have antioxidant activity. There is increasing evidence suggests that flavonoids may affect the activity of enzymes. Paraoxonase 1 is calcium - dependent enzyme that is present in high density lipoproteins. This enzyme has an important role in the prevention of low density lipoprotein oxidation. We investigated the effects of kaempferol, galangin and apigenin from two different chemical subclasses of flavonoids on serum paraoxonase 1 activity and stress oxidative parameters in male rats.  

Materials and Methods: 40 rats (weighting 250±20 g) were randomly divided into four groups. Each group subdivided into two equal subgroups. Subgroups received a dose of 10 mg/kg or 20 mg/kg of flavonoid. Flavonoids were dissolved in ethanol 10%, and given by oral gavage once a day for two months. After that, paraoxonase activity was measured by spectrophotometric method regarding the amount of para Nitro phenol production at a wavelength of 412 nm. The malondialdehyde and total antioxidant capacities were measured respectively by the thiobarbituric acid and the 1,1-Diphenyl-2-picryl-hydrazyl reduction method.

Results: The results obtained from the direct effect of selected flavonoids on augmentation serum paraoxonase activity and prevention of malondialdehyde production in comparison with the control group was as follows: kaempferol> Galangin > apigenin.

Conclusions: Results confirm that structural differences in C3-OH and number of hydroxyl groups could have been an important role in increasing serum paraoxonase 1 activity and reduction of oxidative stress parameters