2.8.1. Enzymatic Antioxidants

The enzymatic antioxidant barrier was evaluated in saliva and erythrocyte samples by measuring the activity of SOD, CAT, Px and glutathione peroxidase (GPx).

Spectrophotometric evaluation of SOD activity (SOD, E.C. 1.15.1.1) was performed according to Misra and Fridovich [27], based on the adrenaline to adrenochrome oxidation rate. Absorbance measurements were taken at 480 nm wavelength.

Colorimetric measurement of CAT activity (CAT, E.C. 1.11.1.6) was based on the hydrogen peroxide degradation rate [28]. The unit of CAT activity (1 U) was determined as the amount of the enzyme decomposing 1 mmol H2O2 per minute. The measurements were performed at 240 nm wavelength.

The activity of Px (Px, E.C. 1.11.1.7) was determined colorimetrically according to the method by Mansson-Rahemtulla et al. [29] based on the reduction of 5,5 -dithiobis-(2-nitrobenzoic acid) (DTNB) to thionitrobenzoic acid at 412 nm wavelength.

The activity of GPx (GPx, E.C. 1.11.1.9) was measured spectrophotometrically using the Paglia and Valentine method [30], based on the reduction of organic peroxides in the presence of NADPH at 340 nm.
