EXPERIMENTAL VALIDATION OF COSMO-SAC PREDICTIONS FOR DEEP EUTECTIC SOLVENTS IN THE RECOVERY OF PROCYANIDINS B1 AND B2 FROM BRAZIL NUT CAKE

Brazil nut cake (Bertholletia excelsa), a by-product of mechanical oil extraction, has potential as a source of high-value-added phenolic compounds. Among these, procyanidins B1 and B2 stand out as the major phenolic compounds identified in this matrix. Accordingly, these compounds were selected as target molecules for the experimental validation of a previous computational screening of deep eutectic solvents (DES). This study aimed to experimentally validate the COSMO-SAC model predictions for the selected solvents by evaluating their ability to identify efficient solvent systems for recovering procyanidins B1 and B2 from Brazil nut cake. Twenty DES were evaluated, based on two hydrogen bond acceptors (HBAs), betaine and choline chloride ([Ch]Cl), combined with ten hydrogen bond donors (HBDs): 1,3-propanediol, γ-valerolactone, glycerol, 1,3-butanediol, formic acid, acetic acid, lactic acid, tartaric acid, citric acid, and fructose. The DES were prepared at an HBA:HBD molar ratio of 1:1, at 333.15 K, with the addition of 30% water, under stirring at 240 rpm for 30 min. Phenolic compounds were extracted at a feed-to-solvent (F/S) ratio of 100 mg/mL, at 333.15 K, under stirring at 500 rpm for 60 min. The extracts were analyzed by Ultra Performance Liquid Chromatography – Mass Spectrometry (UPLC–MS), and procyanidin B1 and B2 concentrations were expressed in μg/g of Brazil nut cake. The results revealed substantial differences in procyanidin recovery among the DES evaluated. The [Ch]Cl:γ-valerolactone system exhibited the best performance for both compounds, yielding 6.74 ± 0.31 μg/g for procyanidin B1 and 4.07 ± 0.11 μg/g for B2. For B1, [Ch]Cl:Glycerol (5.77 ± 0.12 μg/g) and [Ch]Cl:1,3-propanediol (5.18 ± 0.07 μg/g) also performed well. For B2, the next highest values were obtained with [Ch]Cl:1,3-propanediol (3.90 ± 0.01 μg/g) and [Ch]Cl:Glycerol (3.81 ± 0.09 μg/g). In comparison, the betaine-based systems achieved maximum concentrations of 2.32 ± 0.19 μg/g for B1 and 2.61 ± 0.23 μg/g for B2, both obtained using glycerol as the HBD. Systems containing tartaric and citric acids exhibited low recoveries in both groups, consistent with the thermodynamic model predictions. These findings demonstrate that HBA and HBD selection directly influences extraction performance and highlight the advantage of [Ch]Cl-based systems. The superior performance of [Ch]Cl:γ-valerolactone for both procyanidins underscores its potential for their simultaneous recovery. In conclusion, experimental validation confirmed the most promising DES among those evaluated, demonstrating the potential of computational screening to guide solvent selection and contribute to the development of more sustainable extraction processes and the valorization of Brazil nut cake.

Acknowledgments: CNPq - grant numbers 306753/2025-1; CAPES - Finance code 001 and FAPESP - grant numbers 2022/10368-4, 2024/02091-8 and 2025/21661-2.