## 4 Conclusions  
This study provides new insights into the chemical composition and biological activities of essential oils and hydrolates from different parts of sea fennel (_Crithum martiimum_ L.). The volatile profiles of EOs from the leaves, flowers, and fruits were dominated by monoterpene hydrocarbons, with limonene as the most abundant constituent (up to 74.85%). The hydrolates were more chemically diverse than the EOs and were dominated by monoterpneoids, with terpinen-4-ol found in the highest amount in the leaves (27.8%). The results demonstrate weak antioxidant and enzyme-inhibitory and significant cytotoxic activities, with variations depending on the plant part and extract type. The essential oils showed significant effects against certain cancer cell lines, while the hydrolates exhibited moderate activity, without any toxicity to healthy cells for all the tested extracts.  
These findings highlight the potential of sea fennel extracts for applications in the nutraceutical and pharmaceutical industries, particularly due to their bioactive properties. Further investigations are needed to explore their mechanisms of action, safety profiles, and possible therapeutic applications.  
**Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/biom1505066/s1](https://www.mdpi.com/article/10.3390/biom1505066/s1)]([https://www.mdpi.com/article/10.3390/biom1505066/s1](https://www.mdpi.com/article/10.3390/biom1505066/s1)), Figure S1: Total ion chromatogram of sea fennel essential oils from (a) leaves, (b) flowers, and (c) fruits; Figure S2: Total ion chromatogram of sea fennel hydrolates from (a) leaves, (b) flowers, and (c) fruits; Figure S3: Percentage of metabolically active human embryonic kidney HEK-293 cell line after 24, 48 and 72 h of incubation with different concentrations of sea fennel flower and fruit essential oils; Table S1: Results of linear regression for the cytotoxicity of sea fennel flower and fruit essential oils on healthy HEK-293 cell line.  
**Author Contributions:** Conceptualization, M.P.; methodology, M.P., N.R.M., O.P. and I.G.M.; validation, M.P., N.R.M., O.P. and I.G.M.; formal analysis, L.S., O.P., N.R.M., P.B., J.T., I.G.M. and M.P.; investigation, M.P. and I.G.M.; data curation, L.S., O.P., N.R.M., P.B., J.T., I.G.M. and M.P.; writing--original draft preparation, M.P. and I.G.M.; writing--review and editing, L.S., N.R.M., O.P., P.B., J.T., I.G.M. and M.P.; visualization, N.R.M. and M.P.; funding acquisition, I.G.M. and M.P. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work is part of the PRIMA programme supported by the European Union. Project title: \"Innovative sustainable organic sea fennel (_Crithum martiimum_ L.)-based cropping systems to boost agroobidiversity, profitability, circularity, and resilience to climate changes in Mediterranean small farms\" (acronym: SEAFENNEL4 MED) (URL: [https://seafennel4 med.com/](https://seafennel4 med.com/), accessed on 19 March 2025).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The original contributions presented in this study are included in the article/Supplementary Material; further inquiries can be directed to the corresponding author/s.  
**Acknowledgments:** The authors would like to extend thanks for the scientific research equipment financed by the EU grant \"Functional integration of the University of Split, PMFST, PFST and KTFST through the development of the scientific and research infrastructure\" (KK.01.1.1.02.0018).  
**Conflicts of Interest:** The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.