Recovery and separation of glycyrrhizic acid from Natural Deep Eutectic Solvent (NADES) extract by macroporous resin: adsorption kinetics and isotherm studies.

Natural Deep Eutectic Solvents (NADESs) have emerged as a green and sustainable alternative to conventional organic solvents to extract bioactive compounds. However, the recovery of bioactive compounds from the NADES extracts is challenging, restricting their large-scale applications. The present work investigated the recovery of glycyrrhizic acid (GA) from choline-chloride/lactic acid NADES extract using macroporous resins. GA possesses a wide spectrum of biological activities, and it is extracted from the well-known herb Glycyrrhiza glabra. During resin screening, DIAIONTM SP700 showed high adsorption and desorption capacities. The adsorption kinetics study demonstrated that the adsorption of GA on SP700 followed Pseudo First-order kinetic model. Moreover, the adsorption behaviors were elucidated by the Freundlich isotherm using a correlation coefficient based on a static adsorption study at different temperatures and pH. Furthermore, the thermodynamic parameters, for instance, the change of Gibbs free energy (ΔG*), entropy (ΔS*), and enthalpy (ΔH*), showed that the adsorption process was spontaneous, favorable and exothermic. In addition, the sample after macroporous resin treatment, which is enriched with GA exhibited good anticancer potential analyzed by SRB assay. The regenerated NADES solvent was recycled twice, keeping more than 90% extraction efficiency, indicating good reusability of NADES in the GA extraction process by using macroporous resin.

Kinetics and thermodynamics of lipase catalysed synthesis of propyl caprate.

OBJECTIVE: To investigate kinetics and thermodynamics of lipase-catalyzed esterification of capric acid with 1-propyl alcohol in a solvent-free system for synthesis of propyl caprate. RESULTS: The capric acid conversion of 83.82% is achieved at temperature 60 °C, speed of agitation 300 rpm, molar ratio acid:alcohol 1:3, enzyme loading 2% (w/w) and molecular sieves loading 5% (w/w). The activation energy (Ea) for the reaction was determined as 37.79 kJ mol-1. Furthermore, enthalpy (ΔH), entropy (ΔS) and Gibbs free energy (ΔG) values were found out to be + 90.45 kJ mol-1, + 278.99 J mol-1 K-1 and - 2.35 kJ mol-1 respectively. CONCLUSIONS: The results showed that the lipase-catalyzed esterification exhibits an ordered bi-bi mechanism with capric acid inhibiting the reaction and forming the dead-end complex with the lipase. Under the given set of reaction conditions, the lipase catalysed esterification reaction was anticipated to be spontaneous, referring to the value of the Gibbs free energy change (ΔG). Moreover, the esterification process was found to be endothermic, based on the values of enthalpy (ΔH) and entropy (ΔS).