## 3 Results and Discussion
Although there is no information available in the scientific literature on the effect of St. [PERSON]'s word cellular enzymes on the drying process, as in the case of other herbs, it could also be significant. The speed of enzymatic decomposition reactions depends on the water content and temperature. The high moisture content of fresh plants favors these reactions [20]. The drying process can affect the antibacterial and antioxidant properties of herbs. [PERSON] et al. mention that the activity of polyphenol oxidase (PPO) and peroxidase in herbs is of key importance for the preservation of phenolic and antioxidant compounds in dried herbs because these enzymes catalyze the chemical oxidation of phenolic compounds [20]. Optimum temperatures at which these enzymes retain the highest activity largely depend on the plant they come from; for most plants, it is 20-40 \({}^{\circ}\)C, the temperatures at which they are deactivated vary between 65 and 80 \({}^{\circ}\)C [21; 22; 23]. Lipases catalyze the hydrolysis of ester bonds, releasing fatty acids and organic alcohols. As [PERSON] showed in 1906, in water-deficient environments, the reverse reaction (esterification) or various transesterification reactions may occur [24]. The temperatures at which these enzymes achieve the highest activity and are deactivated are similar to those of the previously mentioned enzymes (PPO and peroxidase) [25]. The temperature in the food dehydroxator used for the tests was kept in the range of 44-49 \({}^{\circ}\)C. At elevated temperature, most likely as a result of the action of lysosomal enzymes, chemical changes occur, which result in the release of simpler compounds from cellular structures [26]. Therefore, with this drying method, much higher amounts of alcohols and short-chain fatty acids (SCFAs) were noticed. Since alcohols and acids can react with each other under these conditions, an increased number of esters has also been recorded. Most likely, higher fatty acids were also released, which, due to their low volatility, were not detected by the HS-SPME technique, whereas methyl and ethyl esters of these acids appeared among the volatile components of the dried herb. The formation of high-chain fatty acid esters is dependent on the drying temperature. These compounds were detected in all parts of the plant dried at the highest temperature (method 3). Only trace amounts of hexadecenoic acid methyl ester were found at lower drying temperatures, while no higher fatty acid esters were detected in the fresh plant. Currently, most of the research on St. John's word is focused on the healing properties of hypericin and hyperforin, but many studies have shown that essential oils present in St. John's word have antioxidant, antibacterial, antifungal and larvicidal properties [27]. These essential oils can be a valuable raw material for the pharmaceutical and cosmetic industries [28]. The oils in St. John's word are produced in the translucent canals and released via the secretory canals. These organelles are located on leaves, petals, sepals and pistilis [29]. In the studied herb, the compounds from the group of monoterpenes (\(\beta\)-cisand \(\beta\)-trans ocimene, \(\alpha\)- and \(\beta\)-pinene, \(\gamma\)-terpinene and limonene) and sesquiterpenes (\(\beta\)-caryophyllen, \(\beta\)-famesene, allaoromandendrene, \(\gamma\)-muurolene, \(\delta\)-cadinene, cedrene) were found in the highest amounts. The optimal drying method should not result in a significant loss of essential oils. St. John's wort dried in a food dehydrator (method 3), compared to other drying methods, retained compounds from the group of mono- and sesquiterpenes, aromatic monoterpenes, aromatic monoterpenoids, sesquiterpenoids and aromatic sesquiterpenes in similar or slightly smaller amounts. The lowest losses when using this drying method have been observed among monoterpenoids. Among the volatile products of St. John's wort, alkanes (20-25%) are one of the most numerous groups.