One of the most widespread Mediterranean halophytes is sea fennel, which is widely used for its nutritional value and beneficial health properties. This study aimed to investigate the differences in phenolic composition and biological properties of sea fennel collected from river shore, estuary, and sea coastal zone, where it was exposed to different salinity levels. The extracts were prepared by microwave-assisted extraction (MAE) and analysed for total phenolics, flavonoids, and tannins, while the content of dominant chlorogenic acid was detected by high-performance liquid chromatography with a diode array detector (HPLC-DAD). Antioxidant activity was tested by the Ferric Reducing Antioxidant Power (FRAP) assay and against two free radicals; Nitric Oxide (NO•) and 2,2-diphenyl-1-picrilhydrazil (DPPH•). The highest content of total phenolics and flavonoids was found in sea fennel collected from the river coast, while the highest concentration of chlorogenic acid (1.64 mg/g) and highest FRAP and DPPH• antioxidant activities were found in the samples growing near brackish water. This study confirmed the influence of a plant`s habitat (salinity level) on its phenolic composition, as well as the influence of an individual compound/phenolic group on the total antioxidant activity of the samples.

Crithmum maritimum L., harvest location, salinity stress, MAE, chlorogenic acid, antioxidant activity

The harvest location of sea fennel (salt exposure) has a significant influence on its chemistry and activity. The highest phenolic content was found in the sample from the river shore. The highest antioxidant activity was found in the extract with the highest concentration of chlorogenic acid.