# Chemical Composition and Antioxidant Activities of Three Bulgarian Garden Thyme Essential Oils
## 4 Discussion
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Values** & **Sample 1** & **Sample 2** & **Sample 3** \\ \hline DPPH, mM TE/g & 165.91 \(\pm\) 1.50 \({}^{\text{a}}\) & 144.93 \(\pm\) 1.33 \({}^{\text{b}}\) & 143.20 \(\pm\) 1.32 \({}^{\text{b}}\) \\ ABTS, mM TE/g & 127.65 \(\pm\) 1.20 \({}^{\text{a}}\) & 126.99 \(\pm\) 1.22 \({}^{\text{a}}\) & 121.68 \(\pm\) 1.20 \({}^{\text{a}}\) \\ \hline \hline \end{tabular} Values with different letters in the same row indicate significant differences (\(p<0.05\)).  
\end{table} 
Table 2: Antioxidant activity of three samples of garden thyme essential oils. Of the allergens described in the Regulation 2023/1545, the following were found in the tested garden thyme essential oils: \(\gamma\)-terpinene (6.58-15.51%), \(\alpha\)-terpinene (1.01-3.24%), \(\beta\)-linalool (0.98-2.31%), \(\beta\)-carophyllene (0.88-0.98%), \(\alpha\)-pinene (0.37-0.46%), \(\alpha\)-limonene (0.23-0.29%), \(\beta\)-pinene (0.16-0.20%), terpinen-4-ol (0.35-0.60%), \(\alpha\)-terpineol (0.16-0.47%), terpinolene (0.06-0.14%), gerani (0.06%), and camphor (0.03-0.08%). Their distribution by structure and functional groups is as follows: monoterpene hydrocarbons (\(\alpha\)- and \(\gamma\)-terpinene, terpinolene, \(\alpha\)- and \(\beta\)-pinene, and limonene); monoterpene oxygen derivatives--alcohols (linalool, \(\alpha\)-terpineol, and terpinen-4-ol), aldehydes (gerani), and ketones (camphor); and sesquiterpene hydrocarbons (\(\beta\)-carophyllene). Their quantities should be taken into account when using the oil in perfumery or cosmetic products. In case of the improper storage of the oil (presence of water, light, heat, and other factors), the contained ester, geranyl propionate, can hydrolyze, and the released acid can increase the values of the acid number, and the alcohol (geraniol) is an allergen. Essential oils that contain thymol are known to exhibit antioxidant activity [1; 24; 39; 63], which the authors explain by its presence. According to some authors [21; 37; 38; 64], the antioxidant activity of garden thyme essential oils is due to the synergistic action of the two phenols thymol and carvacrol, and in the oils we studied, the amount of thymol is high (42.88% for sample 3, 44.09% for sample 2, and 53.55% for sample 1) and that for carvacrol is lower (0.73% for sample 3, 2.33% for sample 2, and 2.00% for sample 1). Other authors [27; 38] consider that the antioxidant activity of garden thyme essential oil is due to non-polar compounds (-CH-), for example, the hydrocarbons \(\gamma\)-terpinene, p-cymene, and \(\alpha\)-terpinene, and in the essential oil we studied, the amount of the first two components is high (\(\gamma\)-terpinene: 6.58% for sample 2, 11.13% for sample 1, and 15.51% for sample 3; p-cymene: 14.25% for sample 3, 14.96% for sample 1, and 25.51% for sample 2). The differences in the established values of antioxidant activity can be explained by the specifics of the two methods used: for the DPPH assay, the reducing ability of the antioxidant in relation to this radical is taken into account, and for the ABTS assay, the radical scavenging ability of the antioxidant in relation to the stable cation radical is measured. The essential oil sample 3 has a weaker antioxidant activity compared to the other samples despite the high thymol content. This may be due to the presence of other aromatic substances in the essential oil with different structures and functional groups affecting its activity [41].