Quillaja and Sapindus saponins influence on effect on solubilization of Polymyxin B peptide antibiotic in aqueous solutions

Knowing and understanding the interactions between surfactants and pharmaceuticals is crucial for the proper and efficient design of drug delivery systems. The goal of such systems is to ensure that the drug is as bioavailable to cells as possible. The subject of this study was the effect of natural surfactants, saponins from Quillaja saponaria Mol. and Sapindus mukorossi L., on the behavior of the antibiotic Polymyxin B in aqueous solutions at 30 C and atmospheric pressure. The conducted research showed that the tested surfactants in the concentration range up to 5 mg mL(-1) did not affect the solubility of the antibiotic, but increased the value of the octanol-water partition coefficient (K-ow). At concentrations of plant saponins from both sources, K-ow slightly increased from 0.19 (control sample) to 0.40 (at 5 mg mL(-1)). The presence of surfactants also led to changes in the particle size distribution of Polymyxin B solutions and also in their zeta potential values. There was also a clear effect of saponins on the freezing point of the Polymyxin solution, but no significant changes in the melting point were observed. The collected results provide new knowledge about the interactions of plant surfactants and peptides based on the example of Polymyxin B, which opens wider possibilities for their use in drug delivery systems.