New solvents for extracting gallic acid from chestnut shells: deep eutectic solvents

Abstract

Chestnut (Castanea sativa Mill.) shell, a byproduct of chestnut processing, is a valuable source of phenolic compounds that have a range of industrial applications. This study investigated the optimization of gallic acid extraction from the outer shell of the chestnut using ultrasound-assisted extraction (UAE) and deep eutectic solvents (DES). A Box-Behnken design (BBD) was employed to determine optimal extraction conditions, considering variables such as extraction time, temperature, water content, liquid-to-solid ratio, material treatment, and DES type. Results indicate that baked chestnut shell samples and choline chloride:ethylene glycol (1:2) DES yielded the highest gallic acid content, with optimal conditions of 70 degrees C, 35 min, 20% water content, and a 10:1 liquid-to-solid ratio. This study highlights the environmental and economic advantages of DES-based UAE, supporting its use as a sustainable method for extracting bioactive compounds for application in the food, pharmaceutical, and cosmetic industries.