Application of Natural Deep Eutectic Solvents in Lectin Extraction: A Case Study with Concanavalin A from Jack Bean (Canavalia ensiformis)

Lectins, especially Concanavalin A (ConA), stand out for their relevance in several biotechnological and medicinal applications, from the purification of glycoproteins to the construction of biosensors and therapeutic systems. Despite its potential, efficient extraction of this protein from jack bean seeds (Canavalia ensiformis) still represents a challenge, mainly due to the low extraction efficiency and aggressiveness of existing conventional methods. In this context, natural deep eutectic solvents (NADES) emerge as a sustainable alternative, being formed by the mixture of two or more natural compounds. These liquid solvents form a stable eutectic system with a low melting point, being adjustable in terms of polarity and viscosity. Furthermore, NADES are considered biodegradable and have low toxicity. These characteristics allow its application in the extraction of sensitive proteins, such as lectins, preserving their biological activity. Given the above, this study aimed to evaluate the efficiency of different NADES formulations in the extraction of ConA lectin from jack bean seeds. The methodology involved the characterization of jack bean seed flour through centesimal composition analysis. The extraction was performed using five NADES in different molar proportions: (Betaine-Citric acid-Glucose 1:1:1); (Choline chloride-Citric acid-Glucose 2:1:1); (Citric acid-Glucose 1:1); (Choline chloride-Lactic acid-Glucose 1:1:1) and (Choline chloride-Glucose 2:1). Protein concentration was determined by the Bradford method and the identification of ConA was confirmed by SDS-PAGE electrophoresis. The results revealed that the flour had a protein content of 28.2%, moisture of 10.7%, lipids of 1.95%, ash of 3.15% and carbohydrates of 56.0%, confirming its potential as a protein raw material. Regarding extraction, the protein yield ranged from 8.03 mg (Choline chloride-Citric acid-Glucose) to 11.40 mg (Citric acid-Glucose), equivalent to 14.2% to 20.2% extraction, respectively. Electrophoretic analysis demonstrated bands in the 25 kDa region, corresponding to ConA, in all extracts. This indicates that NADES can not only extract total proteins but also favor the recovery of the target lectin. It was also noted that the solvents Citric acid-Glucose and Choline chloride-Lactic acid-Glucose conferred slightly better defined bands on SDS-PAGE, suggesting greater concentration or less degradation of the lectin. Furthermore, the low lipid content of the flour contributed to the stability of the process, reducing interference in the analysis. It is concluded that NADES have proven to be promising alternatives to conventional extraction, providing environmental and selectivity advantages. These results open perspectives for the use of NADES in bioactive protein extraction protocols on a laboratory, pilot and industrial scale.