## 3 Results and Discussion
### Biological Activities of Sea Fennel Leaf, Flower, and Fruit EOs and Hydrolates  
Sea fennel extracts have been extensively studied for their bioactive constituents and properties, among which the antioxidant activity has attracted the most interest. Previous studies on Croatian sea fennel populations have confirmed the good antioxidant activity of the non-volatile fractions (polar/phenolic extracts) [14; 15], while the activity of the tested EOs was extremely low [15; 42] due to a high content of monoterepenic hydrocarbons that are known as weak radical scavengers and reducing agents. Therefore, in order to provide novelty in the research, this study focused solely on the antioxidant properties of the corresponding hydrolates (from different plant parts, Table 3), which were characterized by the presence of polar, water-soluble, and, in most cases, oxygenated compounds. To the best of the authors' knowledge, this is first report to compare the antioxidant potential of hydrolates from different parts of the sea fennel plant, namely flowers, leaves, and fruits. As can be seen from the results shown in Table 3, the reducing activity of the samples, assessed using the FRAP method (which measures the ability of antioxidants to reduce Fe\({}^{3+}\) to Fe\({}^{2+}\) under acidic conditions), was not observed. This finding aligns with our previous study [21], where the reducing activity was negligible compared to more potent antioxidants. The DPPH and ORAC method, on the other hand, provided information about the free radical scavenging activity of the samples. The difference was in the fact that the DPPH uses stabile, synthetic radicals, whereas the ORAC method monitors the inhibition of peroxyl radicals, which are common in biological systems. Based on the obtained results, it can been seen that the DPPH method also did not show significant activity, with inhibition percentages ranging from 5.67 for the fruit hydrolate to 6.30 for the leaf hydrolate, respectively. However, for the ORAC method, slight differences were seen between the tested results. The highest activity was detected for the leaf hydrolate (123 \(\upmu\)mTE/L), which was close to previously reported values [21]. The relative weak antioxidant activity of the fruit hydrolate can be potentially attributed to this hydrolate having the lowest amount of teripinen-4-ol compared to the other samples, while the leaf hydrolate had higher levels of (_E_)-carveol and carvone, as well as 10-(acetylmethyl)-3-carene (8.6%), which was not detected in the other two samples. Similar to the antioxidant activity, the enzyme inhibitory activity of sea fennel EOs has been previously studied by various authors [15; 43; 44; 45; 46; 47], but there is limited information on the activity of sea fennel hydrolates. In our previous study, we tested the antityrosinase and anticollegenase inhibitory activity of sea fennel hydrolates [21], whereas this research focused on their activity on AChE and BuChE. The obtained results are presented in Table 3.  
Although several studies have investigated the AChE and/or BuChE inhibitory activity of sea fennel's polar, non-volatile fractions/extracts [44; 48], only two studies, including one from our research group, have investigated the inhibitory activity of EOs [15; 47]. To the authors' knowledge, no study has examined the AChE and/or BuChE activity of hydrolates. [PERSON] et al. [47] investigated the enzyme inhibition activities of a sea fennel EO (from the coastal region of Libya, North Africa) on AChE and detected an IC\({}_{50}\) value of 34.43 mg/mL. However, their EO was characterized by a different volatile profile, with the major constituents being thymyl methyl ether (56.86%), \(\gamma\)-terpinene (16.17%), and ledene oxide (4.32%). In our previous study, EOs from sea fennel flowers and leaves were tested at a concentration of 1 mg/mL, and the IC\({}_{50}\) values were not detected. However, according to the obtained results, the flower EO was more effective at inhibiting AChE, while the leaf EO provided greater inhibition against BuChE.