# Extraction of Bioactive Compounds from _Ulva lactuca_
## 3 Results and Discussion
### Extraction of Phenolics and Carotenoids--Selection of Solvent
#### 3.3.4 Overall Evaluation of the Extraction Parameters Effect  
The total carotenoids' content did not fluctuate significantly for the different biomass to solvent ratios applied, while extraction time and temperature showed a slightly higher impact. Particularly, the increase in temperature to 60 \({}^{\circ}\)C favored the carotenoids recovery, and the highest carotenoid content was obtained from the 12 h extraction under 60 \({}^{\circ}\)C. The total phenolic content increased under increased temperature and biomass to solvent ratio. The effect of extraction time was less significant at 25 \({}^{\circ}\)C and more intense at 60 \({}^{\circ}\)C, whereas the 12 h extraction was the optimum one for both temperatures. A straight comparison regarding the antioxidant capacity of seaweed extracts between different studies is difficult due to biological variation of the raw material and extraction methods; however, previous studies have shown that phenolic compounds are the main contributors to the antioxidant activity of various seaweeds [37]. In this study, the antioxidant activity was the most influenced factor by all the studied parameters, as depicted in Figures 2-4. Therefore, with regards to the total bioactive potency of the extracts, the best biomass to solvent ratio was the 1:10 _w/v_, while the extraction times of 12 h and 3 h were the two most favorable under  
Figure 4: Effect of different extraction temperatures on carotenoids content (**A**), total phenolic content (**B**), antioxidant activity (**C**) and total extraction yield (**D**) of _U. lactuca_ extracted with ethanol/water 70:30 _v/v_ at a biomass to solvent ratio 1:10 _w/v_ and for 12 h extraction time. Experimental data are the mean values of three replications.  
25 \({}^{\circ}\)C and 60 \({}^{\circ}\)C, respectively. The stability of carotenoids is one of the crucial parameters in the consideration of developing commercial products from algae extract. Some carotenoids are thermally and chemically labile; therefore, the process parameters should be optimized in order to produce high-quality products, stable against exposure to light and heat for a prolonged time [39].  
The extraction efficiency expressed as the extraction yield showed a slight increase with the biomass to solvent ratio increase, while no particular effect was found from the parameters of extraction time and extraction temperature. Such findings were also mentioned by the work of [PERSON] et al., 2020 [41], where no statistical differences were observed within each extraction parameter on the extraction yield (%), while the recovery of the individual bioactive compounds was altered according to the parameter extractions such as duration and temperature. In the same study, the yields obtained from conventional extraction of several species of seaweed were in the range of 10.5-19.3%, while in the current study _U. lactuca_ extraction yield ranged between 10% and 15%, depending on the extraction parameters.  
With the main objective of this work being the optimum antioxidant activity, the extracts E3 and E12 are proposed as the optimum ones. The antioxidant activity of these two extracts was equal; nevertheless, the extract obtained under 60 \({}^{\circ}\)C, at 3 h (E12), exhibited higher recovery of total carotenoid and phenolic compounds, and thus it is evaluated as the best one.