**Table 3.**

*Hydrogen donors (HD) by groups.*

Glutathione peroxidase and catalase catalyze hydrogen peroxide reduction to water and oxygen. Thus, they exert a protective effect against oxidative injury (**Figure 1**).

The levels of these enzymes decrease with the decrease in gestational age. Another factor that influences enzymatic antioxidant mechanisms is neonatal development. In neonates with intrauterine growth restriction, the antioxidant enzymes SOD, CAT, and GSH-Px have lower values than in term AGA neonates [12, 13].

In our study, for the assessment of enzymatic antioxidant defense capacity, erythrocyte SOD was measured using the Winterbourn method. Hemoglobin concentration was determined in K3 EDTA samples by the Drabkin method.

**Figure 1.** *Enzymatic antioxidant mechanism.*

Determinations in the study group of preterm neonates compared to the values of the control group including full-term newborns evidenced a statistically significant difference, SOD values being higher in term newborns compared to the group of premature babies [6]. The same results were obtained in the case of SOD measurement using Ransod kits (Cat. No. SD 125, Randox Labs, UK). SOD activity was expressed as the amount of proteins leading to inhibition of 90% formazan (505 nm) using xanthine oxidase to generate superoxide radicals [7].

Other studies, as well as our findings show the fact that antioxidant defense is impaired in neonates. This impairment increases with the decrease in gestational age, but is also influenced by the association of oxidative stress-inducing factors that put a strain on the defective defense mechanisms of the newborn.
