A Sustainable Multistage Process for Immobilizing Bioactive Compounds on Layered Double Hydroxides

Abstract

Hybrid systems with antioxidant properties have been developed by integrating bioactive compounds derived from plant resources with layered double hydroxides (LDHs). Anion exchange has been used to substitute intercalated nitrate anions in Mg-Al LDH with carboxylate anions derived from trans-ferulic acid, rosmarinic acid, and 18β-glycyrrhetinic acid. These organic compounds are known for their powerful antioxidant, anti-inflammatory and antimicrobial properties and are highly suitable for cosmetics, biomedicine, and food packaging. To enhance sustainability, a multistage procedure has been developed with the aim of recovering unexchanged carboxylate anions from residual reaction water, ensuring an environmentally friendly and easily scalable preparation process. The process, adapted for each of the three molecules, allows the production of a consistently high-quality hybrid product containing an organic fraction ranging from 10 to 48% by weight, depending on the specific molecule used. The immobilization of organic compounds has occurred either within the layers of LDH through intercalation or on the external surface through adsorption. Good antioxidant capacity has been exhibited by these powdered hybrid systems, as assessed through both the DPPH and linoleic acid/β-carotene tests. Sustainable production practices are enabled by this innovative approach, which also opens avenues for the development of advanced materials for diverse applications across various industries.