Enhancing Verbena officinalis L. antioxidant yield through natural deep eutectic solvents and MOF synergetic application

Abstract

The bioactive components in Verbena officinalis L. extract have been demonstrated to exhibit remarkable pharmacological properties. However, the active ingredients obtained by organic solvent extraction posed a challenge to their application. In this research, a method was proposed for extracting the active ingredient from Verbena officinalis L., in which MOFs were used as adsorbents and natural eutectic solvents (NADESs) as additives in water. The synthetic MOF with a high surface area and porous structure could disrupt the cell walls and adsorb the target components from the herb. Meanwhile, the abundant hydrogen bonding system and polarity adjustability of NADESs enhanced the dissolution of active ingredients. After optimization, the total extraction efficiency of five target substances could reach 22.99 ± 0.67 mg g⁻¹ by using only 1.52% NADES aqueous solution, and the antioxidant capacity of the extracts was better than that of traditional extraction methods. Additionally, density functional theory revealed that NADESs interacted with the active ingredient through hydrogen bonding, enhancing its dissolution and protecting the active site before it exerted its antioxidant power. The NADES dosage was proven to be the most important factor in the extraction process through machine learning, and a Graphical User Interface model was developed to predict the yield based on input variables. Batch experiments proved that Verbena officinalis L. extracts from different sources were suitable for the technology proposed in this work. This technology utilized the synergistic effect of NADESs and MOFs, thereby not only minimizing solvent costs and eliminating the need for solvent recovery but also demonstrating global application value and fully implementing the green concept.