Purification and Oxidative Scavenging of Total Alkaloids of Piperis longi fructus Based on Adsorption Kinetics and Thermodynamic Theory

An effective method for purifying the total alkaloid components from <i>Piperis longi fructus</i> extract was developed in this study. The adsorption/desorption processes of the total alkaloid components from <i>Piperis longi fructus</i> were established by resin model screening, adsorption kinetics, and adsorption thermodynamics tests. Moreover, the purified powders were analyzed with UPLC-Q-ZENO-TOF-MS/MS and then their antioxidant activity was tested. The Langmuir equation provided a good fit with the experimental results. The thermodynamic study provides a satisfactory fit for the isotherm data, indicating that the adsorption process is characterized by spontaneity (Δ<i>G</i>° < 0), exothermicity (Δ<i>H</i>° < 0), and an increase in entropy (Δ<i>S</i>° < 0). Furthermore, the kinetic adsorption behavior on D101 resin was effectively modeled by pseudo-second-order kinetics. According to this mechanism, we selected the best adsorption parameters and optimized the on-column elution process to effectively enrich the total alkaloid components. The optimal process was as follows: D101 macroporous resin was added to an alcohol solution (crude drug concentration of 2 g/mL) and then concentrated under a vacuum at 45~55 °C (<-0.08~-0.10 MPa) until alcohol-free. Subsequently, the resin was loaded into the column and eluted with 70% ethanol at a flow rate of 2 BV/h for 10 BV to achieve desorption. The present study provides a more efficient method for the enrichment of the total alkaloidal components of <i>Piperis longi fructus</i>, which will lay the foundation for applications in food additives or functional foods in the future.