## 3 Results and Discussion
Our focus was on the quantitative analysis of major phenolic acids present in sea fennel, as follows: chlorogenic acid, neochlorogenic acid, and criptochlorogenic acid to study differences in the vegetation stages of sea fennel and the accumulation of biologically active phenolics in the plants. These phenolic acids were analyzed due to their highest concentrations in Croatian sea fennel samples, as previously reported in our studies [15; 16; 18; 20]. Furthermore, the level of total phenolics, flavonoids, and tannins was also previously determined, as well as the assessment of antioxidant activity using FRAP and DPPH assays. The results indicate that sea fennel leaves represent a promising reservoir of phenolic antioxidant compounds [16; 20]. The chlorogenic acid was the dominant phenolic acid in all 12 months, followed by criptochlorogenic acid and neochlorogenic acid. According to the obtained results, higher concentrations of chlorogenic acid were found in the warmer months, from March to October, peaking in June (60.59 mg/g), with a statistically significant difference from all the other months. Conversely, lower concentrations were noted in colder months (late autumn and winter), starting in November, when the lowest concentration was observed (0.46 mg/g), which was also statistically different from all other months. The results of the Pearson correlation statistics (Table 2) support this finding; chlorogenic acid was positively correlated with the average temperature (r = 0.794, \(p\) = 0.002). Chlorogenic acid, a phenolic compound found in various plant species, is known for its multiple positive biological activities and health-beneficial effects, which is why it has significant potential for a variety of industrial applications [25; 26]. Chlorogenic acid, together with its isomers and higher derivatives, has also been identified as the predominant class of phenolics in sea fennel infusions [27]. [PERSON] and [PERSON] [26] conducted a one-year study on _Crithum martium_ (L.), in which they quantified chlorogenic acid in sea fennel leaves from four different vegetation periods at two sampling sites. They demonstrated that chlorogenic acid accumulation was greater in samples collected under cliffs than in samples collected on sandhills, suggesting that the specimens are exposed to greater stress at these sites. The results of our recently published study on sea fennel collected along the coast showed slightly higher concentrations of chlorogenic acid compared to the results obtained at both locations in the study by [PERSON] and [PERSON] [20; 26]. The results of our study are consistent with the findings of several authors and with the available data on the cultivation of sea fennel in various geographical regions. For example, concentrations of chlorogenic acid in leaves sampled from different areas were as follows: in Algeria, 0.64 g/100 g DW; in Croatia, ranging from 0.56 to 1.63 g/100 g DW; in France, 0.73 g/100 g DW; and in Italy, ranging from 0.81 to 1.19 g/100 g DW [28; 29; 30; 31]. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline
The highest concentrations of neochlorogenic acid and criptochlorogenic acid were recorded in September, reaching 5.05 mg/g and 5.9 mg/g, respectively. The level of neochlorogenic acid from September was statistically different from all other months. Criptochlorogenic acid also differed significantly from all other months, with the exception of July. It also showed a high positive Pearson correlation with average temperature and a negative correlation with relative humidity and relative cloud cover (r = 0.887, \(p\) = 0.0001; r = \(-\)0.623, \(p\) = 0.030 and r = \(-\)0.617, \(p\) = 0.032, respectively), while neochlorogenic acid did not correlate with any of the weather parameters tested. In the colder months, from November to April, a notable decrease in the concentrations of these compounds is observed, demonstrating the influence of seasonal variations in the metabolite abundance.