Glycyrrhiza glabra L. Saponins Modulate the Biophysical Properties of Bacterial Model Membranes and Affect Their Interactions with Tobramycin

The global challenge of antibiotic resistance necessitates innovative approaches to improving the efficacy of existing therapeutics while mitigating their environmental impact. This study investigates the role of saponins derived from Glycyrrhiza glabra root extract in modulating interactions of tobramycin, a broad-spectrum aminoglycoside antibiotic, with model bacterial membranes composed of phosphatidylglycerol. Using Langmuir monolayers and vesicle models, we demonstrated that GgC saponins disrupt lipid packing, increasing membrane fluidity and altering biophysical properties. The addition of saponins at concentrations between 1.25 and 10 mg/L reduces the compressibility modulus of the lipid monolayer, with a decrease ranging from 25 to over 50%. ζ potential and dynamic light scattering analyses indicated that GgC–tobramycin interactions modify the surface charge without causing membrane lysis. These membrane changes could potentially facilitate enhanced interactions of antibiotics with bacterial cells. Importantly, these findings suggest the potential of natural surfactants such as saponins to improve antibiotic efficacy, possibly enabling reduced antibiotic dosages. This study provides insights into using saponins alongside antibiotics as a sustainable approach to addressing antibiotic resistance.