## 3 Results and Discussion
Neoxanthin, lutein, violaxanthin, zeaxanthin, and antheraxanthin are amongst the plant carotenoids that are ubiquitously present in various plants. Their biosynthesis is dynamically regulated throughout the entire lifecycle of the plant and subject to control from various aspects, including developmental stages, environmental influences, and epigenetic regulation [38]. The changes in the carotenoid composition of sea fennel throughout the year can be explained by variations in environmental conditions and by different developmental stages of sea fennel. Specifically, light conditions, including radiation levels and photoperiod, vary between the different monthly harvest periods; spring and summer months are characterized by longer photoperiods and higher light intensity, while autumn and winter months are characterized by shorter photoperiods and lower light intensity. Considering the functional role of carotenoids in plants, the increased content observed in our study could also be due potential stress, especially environmental conditions, in which various stressor for the plants occur. Principal component analysis (Figure 2) was performed to describe and summarize the variations between the different compound classes (EO compounds in the amount > 1%), phenolics and carotenoids over a 12-month period. The first two PCAs describe 84.25% of the variance and differentiate sea fennel samples from February to April in one and all other months (May-January) in the other. The most dominant sea fennel compounds were also determined as factors with the largest contribution to the differentiation of these groups. Limonene from the EO compounds, as well as lutein and \(\beta\)-carotene from carotenoids, had the largest contribution to variance. Limonene levels were quite constant from February to April (71.00-74.19%) and differed significantly from most other months (May-August, November, and January). \(\beta\)-Carotene levels were highly variable in each of these months (from 24.76 in February to 103.03 mg/kg in April) but differed significantly from most other sampling periods in a year. Lutein levels were lowest in the given months; in February, lutein was not even detected, while in March and April, it was found in very low amounts (3.13 and 5.56 mg/kg, respectively) when compared to all other months (from 55.60 in July until 182.48 mg/kg in December). Hierarchical cluster analysis revealed two major clusters. The first cluster was composed of limonene, \(\beta\)-carotene, lutein, and chlorogenic acid, which are the most abundant  
Figure 2: Principal component analysis (**a**) and hierarchical cluster analysis (**b**) of the most abundant compounds from sea fennel leaves during a year period. compounds overall in sea fennel leaves throughout a period of a year. The second major cluster was consistent with two smaller clusters, with sabinene, neoxanthin, (\(Z\))-\(\beta\)-ocimene, violaxanthin, and \(\alpha\)-pinene contributing to first one and 15 remaining compounds, with the smallest abundance amongst the entire year, contributing the second cluster. Whereas most of the major bioactive compounds are drastically reduced in winter/early springtime period, \(\beta\)-carotene levels, excluding the months of February and July (when the flowering stage of sea fennel begins), remain mostly unaffected by the vegetation phase and weather conditions, making sea fennel a valuable nutritional source, even in its phytochemical least abundant period.