Synergistic effect of nanobubbles and ultrasound on hydrophobic natural deep eutectic solvent-based green extraction approach of triterpenic acids from Carya cathayensis Sarg. Husk

Carya cathayensis Sarg. green husk (CSGH), one kind of by-product in the nut industry, contains abundant triterpenic acids. This study explores a green extraction approach of triterpenic acid from CSGH using nanobubbles (NBs) and ultrasound-assisted extraction based on hydrophobic natural deep eutectic solvents (HBDES). Triterpenic acids were identified in CSGH using UPLC-Triple-TOF/MS. The HBDES was designed via Hansen solubility parameters, consisting of thymol and linalool (Thy/Lin), and demonstrated the highest yield of triterpenic acids. NBs were generated in Thy/Lin, with an average size of 237.36 nm and the triterpenic acids yield enhancement. Ultrasonic conditions also affect the total contents of the triterpenic acids extracted by Thy/Lin containing NBs partially due to the characters of NBs under ultrasound. The microstructural changes of CSGH confirmed the synergistic effect between ultrasound and NBs which enhanced the release of triterpenic acids. This proposed technique offers a green and efficient solution for extracting triterpenic acids.