###### Abstract  
The present research is a comprehensive investigation of _Dasycladus vermicularis_ (Scopoli) Krasser 1898 from the Adriatic Sea (Croatia) regarding volatileome-volatile organic compounds (VOCs, mostly nonpolar compounds) and less polar nonvolatile compounds for the first time. Headspace solid-phase microextraction (HS-SPME) and hydrodistillation (HD) were used showing the great volatilome variability among fresh (HS-FrDV and HD-FrDV) and dried (HS-DrDV and HD-DrDV) samples after GC-MS analysis. Aromatic aldehydes were dominant in both fresh and air-dried HS samples with benzaldehyde as the most abundant in fresh samples and decreasing 2.7-3.7 times after drying together with 2-phenylbut-2-enal that was not present after drying. Aliphatic compounds (unsaturated hydrocarbons in HS-FrDV; saturated hydrocarbons in HS-DrDV) were also present. C\({}_{11}\)-hydrocarbons (dictyopterpene C' and dicyopterpene D') were detected in HS-FrDV. (_E_)-Phytol Polar Fractions of Dasycladus vermicularis ([PERSON]) [PERSON] 1898 and the Chemical Composition of Fractions and Macrolga Volatilome. _Pharmaceuticals_ **2022**, 15, 743. [[https://doi.org/10.3390/ph15060743](https://doi.org/10.3390/ph15060743)]([https://doi.org/10.3390/ph15060743](https://doi.org/10.3390/ph15060743))  
Footnote †: journal: _Pharmaceuticals_  
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Footnote 0: _E-mail:_ [EMAIL_ADDRESS]  
utilisation of macroalgae for their antioxidant [3,4], anti-tumour [4], and antiviral properties [5] remains in its infancy. They contain complex structure compounds with a variety of biological activities, such as terpenes (antioxidant, anti-tumour, antifungal, etc. ), alkaloids (antioxidant, anti-tumour, antiviral, anti-inflammatory, antibacterial, neuroprotective, etc. ), and pigments (antioxidant, anti-tumour, anti-inflammatory, antidiabetic and antiobesity, neuroprotective, etc.) [6,7]. _Dasycladus vermicularis_ (Scopoli) Krasser 1898 (fam. Dasycladaceae) is a green macroalga that inhabits rocky substrates of North Atlantic and Mediterranean litteral zones. To survive under increased UV exposure and temperatures, macroalgae developed antioxidant defence mechanisms that activate under the overproduction of reactive oxygen species (ROS), thus reducing/preventing the occurrence of oxidative stress [8]. Photobiological adaptation is strongly influenced by growth location, harvesting season, and environmental pressure, which can result in the variation in antioxidant molecules even among the same species. The Adriatic Sea is an extremely harsh environment characterised by its high salinity, relatively low depth, and oscillations in temperature, which might reflect in the occurrence of a variety of novel bioactive compounds with beneficial properties [9]. Currently available studies on _D. vermicularis_ mostly focused on phenolic compounds with antioxidant and UV-radiation absorption activities such as coumarins and their sulfated metabolites such as 7-hydroxycoumarin-3,6-disulfate [9] and also isocoumarins [10]. There is a lack of data in the literature concerning volatile organic compounds (VOCs) analysis of _D. vermicularis_. Our previous studies [10, 11, 12, 13] showed that there is a great diversity of VOCs (mainly nonpolar compounds) when comparing fresh and air-dried samples of marine algae. This was the reason to analyse both fresh (FrDV) and air-dried (DrDV) samples to determine the VOCs variability of _D. vermicularis_ using gas chromatography-mass spectrometry (GC-MS). In addition to the VOCs analysis, less polar nonvolatile compounds and their in vitro and in vivo antioxidative activities were investigated for the first time in this research. Therefore, full chemical profiles of volatile and nonvolatile polar compounds of _D. vermicularis_ were investigated.