## 3 Results & Discussion
### Comparison of MAE, SLE & SFE  
The selected methods of SLE, MAE, SFE and SFE-10% ethanol were examined for comparison purposes. SLE, MAE and SFE were conducted under optimal conditions [25, 27], while a typical low cosolvent concentration [68, 69] was also examined during SFE-10% ethanol. The extraction conditions of each method are presented in Table 4.  
The extraction yield increased in the following order: SFE (3.32% \(w/w\)) < SFE-10% ethanol (6.70% \(w/w\)) < MAE (11.14% \(w/w\)) < SLE (16.77% \(w/w\); Figure 7a). The simple yet protracted process of SLE resulted in the highest extraction efficiency. Thereinafter, MAE resulted in a 34% decreased yield compared to SLE. However, the duration of MAE was almost 104 times shorter than SLE. The application of SFE led to an 80% reduced yield compared to SLE; nevertheless, it was achieved more than seven times faster. Finally, the addition of ethanol during SFE allowed the co-extraction of more polar compounds enhanced SFE and doubled the extraction yield. In conclusion, among all the performed methods, MAE offered the foremost yield in the shortest possible time and with the lowest solvent requirements. Regarding the phenolic compounds, the use of polar solvents has been reported to favor the extraction of flavonoid glycosides and phenols of high molecular weight, whereas non-polar solvents are considered more effective for phenolic acids, flavonoid aglycons and certain phenolic terpen [70]. It could be assumed that similar types of phenolic compounds were extracted during SLE (11.02 mg\({}_{\text{GA}}\)/g\({}_{\text{extr}}\)) and MAE (9.34 mg\({}_{\text{GA}}\)/g\({}_{\text{extr}}\)) and that the assistance of the conventional extraction via microwave power led to a comparable recovery in reduced time (Figure 7b). On the other hand, SFE probably extracted other phenolic types of lower polarity and led to a slightly enhanced phenolic content (13.80 mg\({}_{\text{GA}}\)/g\({}_{\text{extr}}\)). Finally, the highest phenolic content was derived from SFE-10% ethanol (17.30 mg\({}_{\text{GA}}\)/g\({}_{\text{extr}}\)), probably due to the recovery of several phenolic types of varying polarities. However, the significant experimental error did not allow for safe conclusions. The individual and total chlorophyll content presented an increasing trend in the following order: SFE < SLE < MAE < SFE-10% ethanol (Figure 7c). A polar solvent is considered capable of easily dissolving green pigments [71]. Consequently, the chlorophyll content of SLE (46.65 mg/g\({}_{\text{extr}}\)) and MAE (63.36 mg/g\({}_{\text{extr}}\)) emerged higher than the less chlorophyll selective method of SFE (32.88 mg/g\({}_{\text{extr}}\)). Moreover, the presence of ethanol has been proven efficient for the extraction of chlorophylls during SFE by modifying the solvent's polarity [72]. Therefore, the extract's chlorophyll content derived from SFE-10% ethanol (86.95 mg/g\({}_{\text{extr}}\)) prevailed over the rest of the extracts. \begin{table}
\begin{tabular}{l c c c c} \hline \hline
**Parameter** & **SLE** & **MAE** & **SFE** & **SFE-10\% Ethanol** \\ \hline Solvent-to-biomass ratio & 30 & 22 & 100 & 100 \\ (mL\({}_{\text{solv}}\)/g\({}_{\text{biom}}\)) & 30 & 60 & 60 & 60 \\ Stirring (rpm) & 1 & 1 & 250 & 250 \\ Solvent flow rate (g/min) & n/a * & n/a* & 40 & 40 \\ Microwave power (watts) & n/a * & 300 & n/a* & n/a* \\ Duration (h) & 24 & 0.23 & 3.3 & 3.3 \\ \hline \hline \end{tabular}  
* Not applicable.  
\end{table} 
Table 4: The applied conditions of conventional solid-liquid extraction (SLE), microwave-assisted extraction (MAE), supercritical fluid extraction with CO\({}_{2}\) (SFE), and supercritical fluid extraction with CO\({}_{2}\) and cosolvent addition (SFE-10% ethanol). The total carotenoid content presented an increasing trend with the following order: SLE (19.06 mg/gextr) < MAE (24.88 mg/gextr) < SFE (34.61 mg/gextr) < SFE-10% ethanol (37.60 mg/gextr; Figure 7e). Similarly, the selected carotenoid content followed the same increasing trend (Figure 7d).