## 1 Introduction  
An imbalance between the production of free radicals and the body's antioxidant defenses is called oxidative stress. Free radicals can also arise as a result of the action of external factors (UV radiation, ionizing radiation) and during the defense reactions of the human immune system. The production of free radicals also occurs during the normal physiological processes in cell compartments. An important element in the fight against oxidative stress is compounds that have antioxidant properties, among which polyphenols play an important role. Bioactive substances of plant origin have gained popularity in connection to their wide pro-health and pharmacological properties in the last few years [1]. In recent years, some of the most popular sources of antioxidants among consumers are fruits, vegetables and their preserves. Resveratrol, which belongs to the stilbenes, has a wide biological activity. This antioxidant is mainly found in fruits and their preserves, especially in grapes and in high concentrations in red wine. The phenomenon of the French paradox increased the interest in resveratrol. This relationship has broadened the scope of action on the human body in both the cure and prevention of many diseases [2; 3]. A rich source of resveratrol is knotweed (Polygonum cuspidatum) and, more specifically, its root, which is mainly grown in China and Japan. Black grape varieties are the best natural source of resveratrol and red grapes contain more resveratrol than green grapes. There is 50-100 mg/g of this polyphenol in fresh grape skins and the highest content of resveratrol is found in red grapes of the Pinot noir variety [4; 5]. Berries are also a good source of resveratrol (mulberries, cranberries, bilberries, blueberries, black currants, strawberries, raspberries) and it has also been found in jackfruit, apples, nuts, peanuts and in some herbs. Moreover, this compound has also been found in cocoa, chocolate and tomato peels [6; 7]. In the human body, resveratrol occurs in the small intestine. It is transformed in the liver with the participation of cytochrome P450 and its half-life decay is small and ranges from 8 to 14 min. The final metabolites in resveratrol are conjugated forms with sulfuric or glucuronic acid, which are present in the blood for up to nine hours, after which they are excreted via urine [8]. In their studies, many researchers have confirmed the positive role of resveratrol in preventing cardiovascular diseases by inhibiting lipid peroxidation, reducing the uptake of oxidized LDL cholesterol by macrophages and increasing muscle relaxation smooth vessels and inhibiting platelet aggregation [9]. The anti-inflammatory action of resveratrol is mainly due to its inhibition of the synthesis and secretion of inflammatory mediators, including lymphotoxin, a factor that stimulates granulocyte and macrophages (GM-CSF); interleukin 8 (IL-8); and histamine. In addition, resveratrol can reduce the synthesis and release of interleukins 1 (IL-1) and 6 (IL-6), a chemotactic protein for tumor necrosis factor \(\alpha\) (TNF\(\alpha\)). This inhibition of the inflammatory reaction by resveratrol is also related to its ability to block the translocation of the NF-\(\kappa\)B transcription factor into the nucleus [10]. Moreover, the anti-cancer properties of resveratrol are the result of the participation of resveratrol in the removal of free radicals and their chemical [11]. Static magnetic fields are widespread in our homes and in the environment. Many researchers are looking for an answer to the question of what the effects of the body's exposure to a magnetic field may be. Daily exposure to a magnetic field can negatively affect our cells and tissues and cause diseases. Despite the medical use of static magnetic fields (SMFs) for many years, scientific research does not give a clear answer as to whether a static magnetic field has an antioxidant effect or can cause a disturbance of the oxidation-reduction balance of cells [12; 13].