Title : One plant, two solvents, countless benefits: A sequential dual-phase NADES extraction of pumpkin bioactives
Abstract:
Natural deep eutectic solvents (NADES) have been recognized as sustainable, biodegradable, and nontoxic alternatives to conventional organic solvents in the extraction of bioactive compounds from plant materials. Their adjustable polarity makes them suitable for extracting compounds with diverse chemical characteristics. In this study, a sequential NADES-based extraction method was applied to evaluate the carotenoid and polyphenol content in three different Cucurbita moschata varieties, aiming to assess both extraction efficiency and compound specificity. The extraction protocol was designed to selectively isolate hydrophobic and hydrophilic bioactives from a single plant matrix. In the first step, a hydrophobic NADES composed of octanoic acid and decanoic acid (3:1, molar ratio) was used to extract carotenoids, targeting their non-polar, fat-soluble nature. Previously optimized ultrasound-assisted extraction parameters included a temperature of 50 °C, ultrasonic power of 60% (52.5 W/cm³), a solvent-to-solid ratio of 7 mL/g, and an extraction time of 1 hour (10 minutes for carotenoids, 50 minutes for polyphenols). Carotenoids were subsequently isolated from the hydrophobic extract to obtain purified compounds suitable for quantification. The remaining biomass was subjected to a second extraction step using a hydrophilic NADES (glycerol:urea 1:1) to recover polar compounds, specifically polyphenols. This two-step sequential method enhances total yield while minimizing waste by reusing the same plant material. Comparative analysis among the three Cucurbita moschata varieties revealed considerable differences in carotenoid content, with one variety exhibiting the highest concentration of 548.12 µg β-car/g compared to 73.02 and 84.92 µg β-car/g in the other two. A similar trend was observed for polyphenol content, although inter-varietal differences were less pronounced. The same high-carotenoid variety also showed the highest polyphenol concentration, 8.97 µg GAE/ml, followed by 5.78 and 4.36 µg GAE/ml in the remaining varieties. These findings highlight the importance of variety selection in developing functional foods and nutraceutical formulations. In conclusion, the sequential use of hydrophobic and hydrophilic NADES represents a highly efficient, ecofriendly, and selective strategy for isolating diverse bioactives from pumpkins. Beyond maximizing extraction yields, this method preserves compound bioactivity and aligns with principles of green chemistry. It offers a promising platform for the sustainable valorization of agricultural by-products and the creation of high-value functional ingredients.
