## 2 Main Xanthophylls Present in Microalgae
### Astaxanthin (ASX)  
ASX is a secondary keto-carotenoid with a pink-color containing two additional oxygenated groups on each ring compared to other carotenoids. It is 550 and 11 times more effective as a singlet oxygen scavenger than vitamin E and \(\beta\)-carotene, respectively due to its ability to bind to the cell membrane [70]. Due to its spectacular antioxidant properties, ASX shows higher anti-aging and anti-inflammatory activities than other carotenoids [71].  
\begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Xanthophylls** & **Microalgae** & **Extraction Processes** & **Concentrations** & **Applications** & **References** \\ \cline{3-6} \multirow{3}{*}{Violaxanthin} & _Chlorella allipsoaka_ & Solvent extraction & not determined & [54] \\ \cline{2-6}  & _Chlorella vulgaris_ & Solvent extraction & 3.7 mg/g & Anti-inflammatory activity & [55] \\ \cline{2-6}  & _Chlorella vulgaris_ & Solvent extraction & Mechanical extraction & & [55] \\ \hline \multirow{3}{*}{Canthaxanthin} & _Coalestrella striulata_ var. & & 4.75\% dw & Anti-oxidant property & [56] \\  & _multistrata_ & & 45\% Total carotenoids & Create a tan color & [57] \\ \cline{2-6}  & _Chlorella vulgaris_ & & 45\% Total carotenoids & & [57] \\ \hline \multirow{3}{*}{Cryptoxanthin} & _Spirulina platensis_ & Supercritical fluid extraction & 7.5 mg/100 g & Antioxidant, anti-inflammatory, anticancer, improves respiratory functions, stimulates bone formation and protection, & [58] \\ \cline{2-6}  & _Pandorina moram_ & Maceration & 2.38 \(\mathrm{\SIUnitSymbolMicro g}/\mathrm{g}\mathrm{\SIUnitSymbolMicro g}\) DW & [59] \\ \cline{2-6}  & _Nanochlorum caurapatum_ & Enzyme extraction & not determined & decreases risk of degenerative diseases & [60] \\ \hline \multirow{3}{*}{Diadinoxanthin} & _Odontella aurita_ & Ethanol extraction & 10\% total carotenoids & Antioxidant & [29] \\ \cline{2-6}  & _Pharedactylum tricornutum_ & & 19\% of total pigments & & [61] \\ \hline Diatoxanthin & _Phavedactylum tricornutum_ & Methanol extraction & 17\% of total pigments & Antioxidant & [61] \\ \hline \hline \end{tabular}
\end{table}
Table 1: \(Cont.\)This xanthophyll occurs naturally in a large variety of microalgae such as _Haematococcus pluvialis_ and _Chorella zofingiensis_[72]. _Haematococcus pluvialis_ is the most widely used natural source for the industrial production of this pigment with yields of up to 3.8% DW [32; 33; 73]. It is relatively easy to purify ASX from microalgae because it represents 90% of the total carotenoid content [74]. For all these reasons, various products containing ASX are already available on the international market in diver forms such as soft, oils, syrups, creams, capsules with a market value of USD 1.0 billion in 2019 [16]. Two examples are AstaPure(r) (Algatech Ltd., Kibbutz Ketura D.N, Israel, [[https://www.algatech.com/](https://www.algatech.com/)]([https://www.algatech.com/](https://www.algatech.com/)), accessed on 15 April 2021) and BioAstin (Cynotech Corporation, Kailua-Kona, HI, USA, [[https://www.Cyanotech.com/](https://www.Cyanotech.com/)]([https://www.Cyanotech.com/](https://www.Cyanotech.com/)), accessed on 15 April 2021) produced from the microalgae _Haematococcus pluvialis_.