An efficiency strategy for extraction and recovery of ellagic acid from waste chestnut shell and its biological activity evaluation

Chestnut shells in large amounts are significantly underutilized agricultural and forestry waste that can be exploited as a resource for the production of high-valued nature active compounds. In this study, an efficient and green approach was established to extract and recover the highly valued phenolic compound, ellagic acid, from waste chestnut shells with choline chloride-based deep eutectic solvents (DESs). By utilizing optimized ultrasonic-assisted extraction conditions with choline chloride/n-propanol DES, solid–liquid ratio of 40 mg/mL, extraction time of 70 min and extraction power of 200 W, highly efficient extraction value for ellagic acid of 4.64 mg/g was obtained. Meanwhile, ellagic acid was recovered easily with a recovery percentage of 94.9% by anti-solvent precipitation method through the denaturation of DES with water. The purity of ellagic acid in the extracts reached 85.6%, which is more than two times to that via ethanol extraction methods (36.4%). In addition, the recovered ellagic acid exhibited strong antioxidant activity with IC50 (0.309 mg/mL) and significant antibacterial activity with Minimal inhibitory concentration (MIC) (250 mm) and diameter of inhibition zone (DIZ) (17.60 μg/mL). The anti-solvent precipitation method could denature DES, led to higher extraction and recovery efficiency and high-purity ellagic acid simultaneously in one step. The novel method is of great significance to the whole chestnut production process for the utilization of waste chestnut shells. Furthermore, this method can also be used as a green, pollution-free alternative method for the extraction and recovery of phenolic components from natural resources for pharmaceutical and biochemical applications.