A paradigm for natural eutectic solvents based on fatty acids: Molecular interactions and toxicological considerations
Sonia Martel-Martín, Maria Enrica Di Pietro, Alberto Gutiérrez, Núria Aguilar, Alfredo Bol, Santiago Aparício, Fatima Matroodi, Barbara Rossi, Andrea Mele
Abstract
• Menthol and C8 – C10 fatty form a paradigmatic type V hydrophobic eutectic solvent (V-HDES). • Both H-bond and dispersive interactions contribute to the liquid structuration. • The formation of cyclic hetero-dimers via intermolecular and interspecies H-bonds is predicted by DFT and MD. • COSMO-RS predicts several thermodynamic properties of V-HDES. • In silico toxicological profile suggests V-HDES - human target proteins interactions. In this work, we present experimental and molecular modeling results on archetypal hydrophobic natural deep eutectic solvents (NADES) based on fatty acids (octanoic and dodecanoic acid) and menthol, a representative monoterpenoid. Our goal is to provide a multiscale characterization to enhance the understanding of this field by studying these selected archetypical mixtures. We examine their liquid state properties, intermolecular forces, nanoscopic arrangements, toxicity, and environmental impact. The computational study integrates quantum chemistry, molecular dynamics (both all-atom and coarse-grained approaches), and thermodynamic modeling (COSMO-RS approach) to analyze the fluids and their interactions with biological entities, such as proteins and plasma membranes. The experimental characterization focuses on elucidating intermolecular interactions and liquid phase dynamics using NMR spectroscopy, visible and UV Resonance Raman spectroscopy (UVRR). Notably, this is the first report of UVRR data on NADES. Additionally, we simulate the effect of the molecular moieties forming the solvents on biological targets—specifically, protein and cell membrane models –. This in silico analysis aims to rationalize and predict their potential toxicity. Overall, our experimental findings and in silico simulations contribute to a deeper understanding of these novel solvents in terms of their network of interactions. Additionally, they highlight the potential impact on biological targets, providing new data to accurately define the eco-friendliness of type V DES and their suitability as sustainable alternatives to traditional molecular solvents.