Optimization, Kinetics, and Thermodynamics of Ultrasound-Assisted Extraction of Phytochemicals from Hemp

Hemp (<i>Cannabis sativa</i> L.) is a rich source of bioactive compounds, yet efficient extraction strategies that maximize beneficial cannabidiol (CBD), phenolics, and flavonoids while minimizing the psychoactive tetrahydrocannabinol (THC) remain insufficiently explored. This study aimed to bridge this gap by optimizing ultrasound-assisted extraction (UAE) of phytochemicals from hemp and elucidating the underlying kinetics and thermodynamics. Using response surface methodology (RSM), optimal conditions within the tested range of 5-15 mL g^-1 liquid-solid (L-S) ratio, 45-65 min, and 10-30 °C were determined as 10 mL g^-1, 45 min, and 18 °C. Under these conditions, CBD yield reached 222.45 mg gDW^-1, total flavonoid content (TFC) 2.75 mg CAE gDW^-1, and total phenolic content (TPC) 11.13 mg GAE gDW^-1, while THC content was reduced to 25.74 mg gDW^-1. Kinetic modeling indicated a first-order model for CBD, a power law model for THC, and Peleg's model for TPC. Thermodynamic parameters were estimated via both van't Hoff and Eyring analyses, incorporating error propagation and confidence intervals. The results revealed distinct compound-specific behaviors. These findings not only clarify the extraction behavior of key hemp phytochemicals but also provide practical insights for developing precise, efficient, and sustainable hemp-processing strategies for food, cosmetic, and other value-added applications.