## 3 Results and Discussion
Sea fennel contains isomers of chlorogenic acid (CGA), among which chlorogenic, cryptochlorogenic, and neochlorogenic acids stand out as prominent compounds [12], which is consistent with the results of our study. However, in Greek sea fennel genotypes, the CGA isomer 5-coumaroyl-quinic acid surpasses chlorogenic acid in frequency [32]. Such results point us to botanical diversity, which enriches our understanding of the chemical composition of sea fennel and highlights the importance of geographical factors in shaping plant metabolite profiles. Lower concentrations of phenolics can also be explained by the fact that plants undergo a period of dormancy or reduced growth during a period of late autumn and winter (colder) months. Additionally, halophytes can synthesize secondary metabolites in response to oxidative damage caused by various stressors, primarily due to their antioxidant properties, which are highly valued in human nutrition [33]. During warm weather, halophytes may encounter multiple stressors, such as salinity, temperature fluctuations, and variations in water availability. These stressors, which are prevalent in spring and summer periods, collectively stimulate the biosynthesis of phenolic compounds in halophytes, contributing to the heightened phenolic content observed during these seasons [34]. Three xanthophylls (neoxanthin, violaxanthin, and lutein) and one caroten (\(\beta\)-carotene) were quantified in sea fennel leaf samples collected throughout the year using UHPLC-UV/Vis-DAD. In all samples analyzed, the predominant compound was lutein, followed by \(\beta\)-carotene. Violaxanthin and neoxanthin were also detected, but in significantly lower concentrations, or they were absent in some of them. According to our results, the highest concentrations of the measured carotenoids were observed from August to January. Specifically, the maximum concentration of lutein was recorded in December (182.48 mg/kg), \(\beta\)-carotene in August (173.79 mg/kg), violaxanthin in October (15.07 mg/kg), and neoxanthin in January (8.72 mg/kg). Lutein and \(\beta\)-carotene were also statistically different from all the other months analyzed in the given period. Carotenoid levels did not correlate with temperature for several EO compounds and phenolics. The only mild correlation was observed for relative humidity and lutein levels. Violaxanthin was not detected between April and October (except in June), with a decrease in concentration observed in November and December, followed by irregular growth. Neoxanthin was also not detected between February and April, as well as in December. In December, lutein reaches its maximum concentration, which then decreases drastically during winter months, with the minimum concentration measured being 3.13 mg/kg. \(\beta\)-carotene peaks in August, following a significant drop in concentration in February (24.76 mg/kg). To our knowledge, information on the concentration of individual carotenoids is quite limited. [PERSON] et al. [35] reported on the carotenoid contents in Italian wild and cultivated sea fennel leaf samples, in which the concentration of neoxanthin ranged from 6.12 to 21.29 mg/kg, violaxanthin from 2.35 to 41.04 mg/kg, lutein from 102.54 to 190.89 mg/kg, and \(\beta\)-carotene from 26.59 to 111.05 mg/kg, which is consistent with our findings. Carotenoids not only play a crucial role in the physiological processes of plants and the functional dissipation of excess solar energy for photosynthesis but also contribute significantly to the overall appeal of edible fruit and vegetables. They are responsible for imparting the vibrant colors of these foods and serve as precursors of many important volatile flavor compounds [36]. In addition, carotenoids possess antioxidant properties,and some of them (such as \(\beta\)-carotene) are provitamin A components, so their consumption reduces the risk of various cancer types, as well as ophthalmological or cardiovascular diseases [37].