Natural deep eutectic solvent (NADES)-aided extraction of bioactive compounds from cotton byproducts for agricultural applications: Extraction optimization, structural identification, and bioactivity evaluation
Haibin Wu, Haibin Wu, Ganyu Zhang, Yong Zhang, Peng-xin Guo, Haibo Wu, Haibo Wu
Abstract
This study pioneers the application of natural deep eutectic solvents (NADES) for the green extraction of bioactive compounds from cotton ( Gossypium hirsutum L.) byproducts, with a focus on optimizing phenolic, flavonoid, and gossypol recovery while evaluating their multitarget agrochemical potential. Among the nine NADES formulations tested, proline-citric acid (Pro-CA) exhibited superior efficiency in terms of the phenolic yield (2.2 × more than ethanol) and gossypol yield (4.8 × more than ethanol). Bioactivity assays revealed that Pro-CA extracts exhibited marked antifungal, nematicidal, and insecticidal activities, outperforming synthetic controls. Correlation analysis revealed that the gossypol content was the primary bioactivity driver, showing strong associations with antifungal, nematicidal, and insecticidal effects. Response surface methodology optimized extraction conditions (liquid solid ratio: 35.93 mL/g; temperature: 61.42°C; time: 90.69 min) achieved a 7 × greater gossypol yield than ethanol. Phytochemical isolation yielded 21 gossypol derivatives, including 2 novel analogs and 19 known analogs. Bioactivity tests revealed that gossypols 1 , 2 , 3 , 5 , 8 and 9 had markedly stronger antifungal effects against four phytopathogenic fungi than did carbendazim. Compared with abamectin, gossypols 1 , 2 , 4 and 9 showed high nematicidal activities (LC 50 , 16.29–22.13 mg/L) against Meloidogyne incognita . Gossypols 1 − 4 showed marked insecticidal activities (IC 50 , 6.67–11.36 mg/L) against Bostra odoriphaga , outperforming azadirachtin. The structure activity relationships revealed quinone moieties and hydroxyl groups as critical for antifungal activity, whereas lactone structures increased insecticidal potency. This work establishes the use of NADES as a green platform for valorizing cotton byproducts into multifunctional agrochemicals, providing a scientific foundation for sustainable agricultural practices.