Unveiling the role of the ring size in the sugar-based tensides surfactancy by interfacial studies and molecular dynamics

Sugar Fatty Acid Esters (SFAEs) are a class of biosurfactants that are gaining growing attention due to their excellent emulsifying, stabilizing and detergency properties; moreover, they show several advantages over their petroleum-based counterparts being non-toxic, fully biodegradable and environmentally friendly. Herein, a series of alkyl 6-O-palmitoyl-D-glucosides were enzymatically synthesized by reacting alkyl D-glucoside isomeric mixtures with molten palmitic acid in an easily scalable solvent-free system. Couples of anomers, namely pyranosides-(Py) and furanosides-based compounds (Fu), were isolated through flash column chromatography. Investigation of interfacial tension (IFT), water-in-sunflower oil (W/O) emulsifying capability and subsequent stability over time by turbidimetric and confocal microscope analyses indicated strong differences in their physico-chemical properties, with Py-derivatives showing better surfactancy with respect to that of Fu ones. Furthermore, computational studies were performed aiming at both unravelling the role of ring size (Py vs Fu) in the surfactant mixtures and at evaluating the water-in-oil emulsion formation and stabilization.