# Seasonal Monitoring of Volatiles and Antioxidant Activity of Brown Alga _Cladosteplus spongiosus_
## 2 Results and Discussion
### Non-Target Screening of Non-Volatile Compounds in Ethanol Extract
They can be classified into three groups based on the nature of the glycosyl and acyl structures: monogalactosyl diacylglycerols (MGDG), digalactosyl diacylglycerols (DGDG), and sul  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**No. ** & **Name** & **Monoisotopic** & **[M + H]+** & **Molecular** & **t\({}_{\mathbf{R}}\)** & **Mass Difference** & **Area** \\  & & **Mass (Da)** & **Formula** & **(min)** & **ference** & **(Ppm)** & **(Counts)** \\ \hline  & & **PIGMENTS AND DERIVATIVES** & & & & & \\  & & 4,8,13,18-tetramethyl-20-oxo-9,14- & 586.22162 & 587.2289 & C\({}_{35}\)H\({}_{30}\)N\({}_{4}\)O\({}_{5}\) & 15.67 & 0.9 & \(3.11\times 10^{6}\) \\  & & & & & & & \\  & &  
foquinovosyldiacyl glycerols (SQDG) [49]. MGMG is a byproduct of the degradation of accumulated MGDG in the outer membrane of chloroplasts [50]. In the group of pigments, one chlorophyll \(a\) derivative (pheophorbide \(a\), compound **21**), one demetallized chlorophyll \(b\) (pheophytin \(b\), compound **27**), three pheophorbide derivatives (compounds **22**, **23**, **25**), one xanthophyll and two derivatives (compounds **15**, **16**, **28**), and one monoterpene lactone (loliolide, compound **1**) were detected (Table 4). The pigments are known antioxidants [51; 52]. Pheophorbide \(a\), a derivative of chlorophyll \(a\), has been extracted from marine algae and has shown great antitumor activity [53]. Among the pigments, it was the most abundant in the extract (Table 4), which contributes to the antioxidant activity of the extract. [PERSON] et al. [54] studied the green alga _Ulva prolifera_ (formerly _Enteromorpha prolifera_) and its ethanolic extract, which showed high antioxidant activities. The later subfraction with chloroform showed the strongest antioxidant activity of all subfractions, and further spectroscopic analysis revealed the pheophorbide \(a\) as the major compound. Fucoxanthin, the major xanthophyll in brown algae [55; 56], and xanthophyll derivatives, halocymithiaxanthin acetate and loroxanthin decenoate, were detected. [PERSON] et al. [57] reported fucoxanthin in _C. spongiosus f. verticillatus_. Halocymithixanthin acetate and loroxanthin decenoate are more abundant in green algae [58]. Xanthophylls exhibit diverse bioactive properties, such as antioxidant, antitumor, and anti-inflammatory activities [55; 56; 59]. The antioxidant activity of the extract might be related to the high amounts of fucoxanthin (Table 4). [PERSON] et al. [60] evaluated the potent antimicrobial activity against Gram-positive and Gram-negative bacteria and fungi and the strong antioxidant activity of fucoxanthin extracted from _Dictyota fascola_ (formerly _Dilophys fascola_). Fucoxanthin is one of the most studied xanthophylls against cancer cells because of its antiproliferative effect [59]. Halocymithiaxanthin is a metabolite of fucoxanthin and has shown even stronger cytotoxic results than fucoxanthin when tested on human neuroblastoma cells [61]. [PERSON] et al. [62] studied the biological activity of the marine green alga _Tetraselmis suecia_, whose ethanolic extract contained a high proportion of xanthophylls, among which loraxanthin esters were present. The extract showed potent antioxidant activity and antitumor activity against human lung cancer line (A549). Loliolide, the only monoterpernoid lactone detected in our study, was previously detected in _C. spongiosus f. verticillatus_ by [PERSON] et al. [57]. It has also been detected in the genus _Ericaria_[28], _D. vermicularis_[40], and the microalgae _Tetraselmis obliquus_[63]. [PERSON] et al. [64] demonstrated the neuroprotective, anti-inflammatory, and antioxidant effects of loliolide in an extract of _Codium tometosum_.