## 4 Discussion
On the basis of the obtained results, it was suggested that resveratrol may not be significant for the heath-promoting properties of red wine. At the same time, [PERSON] et al. [88] proved that resveratrol requires the presence of other polyphenols to exert its optimum antioxidative activity. It is also emphasized that resveratrol has low bioavailability and possible side effects [83], including pro-oxidative and cytotoxic effects, depending on the dose and time of exposure [80]. Considering the fact that some polyphenols, including resveratrol, were not studied in the present research, it would be valuable to include them in further studies, as it is necessary to verify the obtained results because they suggest an important association between polyphenols of red wine and oxidative stress parameters in growing organisms. The present study revealed statistically significant influence of red wine intake and intake of phenolic acids (hydroxybenzoic acid, caffeic acid, p-coumaric acid, ferulic acid, and sinapic acid) and anthocyanins (cyanidin, cyanidin 3-glucoside, cyanidin 3-rutinoside, delphinidin, and pelargonidin) on TBARS and protein carbonyl group levels, but the influence was observed only for a period of two weeks. The obtained results may suggest pro-oxidative effect of both ethanol and polyphenols on the liver of growing male rats. Moreover, after a period of four and six weeks, there was no influence on TBARS and protein carbonyl group levels; thus, it can be hypothesized that prolonged exposure of ethanol and polyphenols triggers an adaptive mechanism in growing organisms. In spite of the fact that the conducted study did not allow to indicate which compounds of red wine were responsible for the observed effect, some important contributions of the presented study should be indicated. The most important observation is associated with the differences for the periods of two, four and six weeks. Moreover, as so far there were only some studies for growing organisms, the possibility of adaptive defense of the young organisms is also a novel observation. As a result, further studies are needed to confirm the mechanism of the pro-oxidative effect of polyphenols present in red wine on the liver of growing organisms. In spite of the fact that the conducted study revealed a novel interesting observations, some limitations of the study must be listed. The most important issue is associated with the fact that the study was conducted in animal model, so transferring the observations into population is straitened. The other significant limitation is associated with the scope of the study--as only TBARS and protein carbonyl groups were included for the analysis, and some other factors also being markers of oxidative stress were not planned to be included. In the previous own study, it was indicated that alcohol consumption may have influenced hepatic antioxidant defense, while the catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase, transferase (GST), reductase activities, total antioxidant status, and glutathione level (GSH) were analyzed [39]. However, to the conducted study, neither indicated parameters, nor the other factors (e.g., trolox equivalent antioxidant capacity (TEAC), cytochrome P450), were planned to be included. Similarly, in the future studies also other polyphenols should be included, such as quercetin and epicatechin, being among the major polyphenic compounds of red wine [89]. The other important limitation results from a sample size which was sufficient for animal model study, but requires to be reproduced in a larger studies and also in a different models (including experiments for different red wines). The other issue is associated with the applied research methodology and tissue preparation, as some recent studies indicate that not only mild to moderate hypothermia should be applied, but also perfusion should be included to maintain hepatic viability and reduce oxidative stress which may influence TBARS results [90; 91; 92] and it is applied in some studies [93].