Exploring polar hydrophobicity in organized media for extracting oligopeptides: application to the extraction of opiorphin in human saliva

Supramolecular solvents (dubbed SUPRAS) are gaining momentum as extractants of compounds of interest from complex matrixes such as foodstuffand biological and environmental samples. However, their powerful extraction mechanism, based on multiligand ability for solute binding, fails when applied to very polar compounds, hindering their applicability to the extraction of highly polar metabolites. In this work, we introduce the synthesis, characterization, and application of a new kind of SUPRAS formed by heptafluorobutyric acid (HFBA). The polar hydrophobicity of this perfluorinated acid results in a SUPRAS, which coacervates at acidic pHs, that shows a great capability to extract amino acids and oligopeptides (recoveries in the range 81-105%) with nonpolar alkyl, cyclic or aromatic side chain substituents (with log D > -3.62). To further demonstrate the potential of this novel SUPRAS, an analytical methodology for the determination of opiorphin in real saliva samples was developed and fully validated. The HFBA-based SUPRAS was synthetized in situ from 950 mu L of stabilized saliva, by the addition of 150 mu L of HFBA and 400 mu L of HCl 37% (v/v). The resulting SUPRAS was directly injected into a LC-MS/MS system for further quantification. Quantitative recoveries in the range of 87-110% were obtained with relative standard deviations below 20%. The HFBA-based SUPRAS is, therefore, capable of efficiently extracting opiorphin from saliva samples and shows a high potential for the determination of several amino acids and oligopeptides from biological samples. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The HFBA-based SUPRAS shows excellent extraction capability for amino acids and oligopeptides from complex matrixes. The development of an analytical methodology for the determination of opiorphin in saliva samples further demonstrates its potential for applications in biological samples.