## 3 Results and Discussion
### Screening of NADES for Phytochemical Recovery Across Diverse Plant Matrices
While early DES systems demonstrated betalain extraction potential, the NADES offers distinct advantages, including biocompatibility and alignment with green chemistry principles. The efficiency of solvents in extracting carotenoids from dried carrots and sweet potatoes is presented in Figure 2. Unfortunately, acetone outperformed all other solvents, yielding the highest carotenoid content for both matrices: 0.020 mg/g in carrots and 0.040 mg/g in sweet potatoes. These values significantly exceeded those of NADESs and water. Among the NADES formulations, NADES4 demonstrated moderate efficacy, extracting 0.009 mg/g from carrots and 0.018 mg/g from sweet potatoes. Water showed limited efficiency, yielding 0.015 mg/g for both matrices, and it outperformed most NADESs. The results indicate that acetone is superior, likely because of its more non-polar properties compared to the NADES, which aligns with carotenoid solubility. While NADES4 showed promise, its lower efficiency compared to acetone suggests room for formulation refinement. The substantial underperformance of NADES1, NADES2, NADES3, and NADES5 underscores the importance of solvent composition in tailoring extraction protocols. Carotenoids, such as \(\beta\)-carotene, are highly non-polar compounds requiring solvents with compatible polarity to facilitate dissolution. Polar NADESs, composed of hydrophilic components like choline chloride, urea, and organic acids, form hydrogen-bonding networks that favor interactions with polar phytochemicals but exhibit poor affinity for hydrophobic molecules. This poor performance stems from a hydrophobicity mismatch, as carotenoids require solvents with non-polar affinity. Researchers have utilized a range of eutectic mixtures, known as HDESs (hydrophobic deep eutectic solvents), for extracting lipophilic compounds from various food matrices, including pumpkin (_Cucurbita maxima_), carrot peels, and _Citrus sinensis_ peels [27; 28; 29]. Figure 2: The impact of solvents on carotenoid extraction (mg of \(\beta\)-carotene/g of dry matter) from dried carrot and dried sweet potato. Error bars represent the standard deviation (SD) of three independent measurements. The values with the same uppercase letters (A–D) for dried carrot or lowercase letters (a–d) for dried sweet potato do not differ significantly (\(\alpha=0.05\)). [PERSON] et al. [27] introduced fatty acid-based and menthol-fatty acid eutectic solvents to enhance the solubility and extraction efficiency of \(\beta\)-carotene. Among the twelve hydrophobic NADES formulations tested, a caprylic acid to capric acid ratio of 3:1 demonstrated the best performance, i.e., \(\beta\)-carotene solubility of 200.77 \(\mu\)g/mL and an extraction efficiency of 96.74 \(\mu\)g/mL. By combining this formulation with ultrasound, the extraction parameters for carotenoids from pumpkin were optimized using the Response Surface Methodology (RSM) and the Artificial Neural Network (ANN). The highest \(\beta\)-carotene yield of 151.41 \(\mu\)g/mL was obtained at 50 \({}^{\circ}\)C, utilizing 60% ultrasonic power and a solvent-to-solid ratio of 7 mL/g. Additionally, the authors discussed the concept of switchable solvents, specifically by the addition of ammonium hydroxide, which transformed the NADESs from hydrophobic to hydrophilic. This alteration facilitated carotenoid precipitation, achieving a 90% recovery rate, with \(\beta\)-carotene as the primary compound recovered at 52.25% [27]. Menthol and other terpenoids, such as thymol and camphor, were also used as part of hydrophobic deep eutectic mixtures to extract carotenoids from carrot peels. In the initial studies, the combination of thymol and menthol showed 1.281-1.338 mg of \(\beta\)-carotene/mL of total carotenoids; however, it was surpassed by acetone, which measured 1.612 mg/mL. Then, a Box-Behnken design was used to optimize extraction parameters: a thymol/DL-menthol molar ratio of 1:4, a solvent-to-sample ratio of 10:1 (\(v/w\)), and an extraction time of 30 min.