Investigations into the Structure-Function Relationship of the Naturally-Derived Surfactant Glycyrrhizin: Emulsion Stability

Abstract

This study describes the emulsion stabilizing properties of the licorice root (Glycyrrhiza glabra L.) derived saponin glycyrrhizin and its corresponding aglycone 18β-glycyrrhetinic acid to further increase the understanding between structure and functional behavior. For this, we prepared 10% oil-in-water emulsions and investigated the emulsion stabilizing properties regarding environmental stresses including extreme pH, ionic strength, and temperature. Glycyrrhizin and its aglycone formed nanosized emulsion droplets at neutral pH that were stable across a broad range of pH-values (pH 5-9), ionic strength (0-200 mM NaCl), and temperature (up to 60°C). In contrast, emulsions were unstable at low pH (pH <5), as well as high ionic strength (>200 mM NaCl, >5 mM CaCl 2) and temperature as well as after a freeze-thaw cycle. Thereby, the observed instability was mainly attributed to the reduction of electrostatic forces caused by the protonation of free carboxylic acid groups at low pH, screening of electrostatic forces at high ionic strengths, and thin interfaces causing coalescence during a freeze-thaw cycle. Overall, both molecules yielded remarkably stable emulsions at very low molecule-to-oil ratios, and therefore our results are relevant for 'all-natural' emulsion-based foods and beverages, as well as pharmaceutical and cosmetic products.

Glycyrrhizic Acid Inhibits SARS-CoV-2 Infection by Blocking Spike Protein-Mediated Cell Attachment

“…Cinatl et al showed that GA was effective against SARS-CoV [ 12 , 44 ]. The reported concentrations for GA antiviral effect in cell cultures generally vary between 1 and 5 mM concentrations, at which concentrations GA can form an emulsion or long-lasting foams in an aqueous solution [ 45 , 46 , 47 ]. It is well known that surfactants were able to inactivate enveloped viruses by causing protein aggregation, disruption of the envelope, or by distorting the shape of virions [ 48 ].…”

Improving the gastrointestinal activity of probiotics through encapsulation within biphasic gel water-in-oil emulsions

“…The overall stability of emulsion not only affects its shelf life, but also one of the most basic properties of the encapsulated active ingredient as the delivery system. 28 In food processing, the encapsulation system needs to maintain its high stability under the changing state in order to protect the beneficial components. The transmission spectra of different W/O emul- This may be that some samples adhered to the inner side of the sample tube during sample addition, resulting in a slight change in the light transmittance at the early stage of the test.…”

Recent Advances and Applications of Plant-Based Bioactive Saponins in Colloidal Multiphase Food Systems

“…Weiss and coworkers recently investigated the emulsifying properties of GA monomers at pH 7.0 and showed that the GA (0.01–5 mM) can form stable oil-in-water emulsions (10 wt% oil) with a d 32 value of around 0.2 μm [ 89 ]. These emulsions are found to have good stability under various environmental stresses, including a wide range of pH values (5–9), salt concentrations (0–200 mM NaCl) and temperatures (up to 60 °C) [ 90 ].…”