A Molecularly Imprinted Polymer for Selective Extraction of Phenolic Acids from Human Urine

Marco Mora-Granados,David González-Gómez,Alejandrina Gallego-Picó,Jin Su Jeong

doi:10.3390/app11041577

Abstract

Studies for monitoring the bioavailability of dietary flavonoid compounds generate great interest. Among them, low-molecular-weight phenolic acids, secondary metabolites present in colonic catabolism and urinary excretion, have been proposed as biomarkers of polyphenol intake. Using 4-hydroxyphenylacetic acid as a template, a molecularly imprinted polymer (MIP) was synthesized for selective extraction of these hydroxylated metabolites from human urine samples and posterior analysis in an HPLC-DAD-MS system. Polymers were characterized by Scanning electron microscopy (SEM), Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), Brunauer-Emmett-Teller (BET) method, and binding experiments. MIP presents specific recognition ability for template and analogues molecules. This capacity of recognition and the pH dependence of the binding strength was also studied. The method was validated over a concentration range of 0.25–40 mg/L, r2 > 0.995. In the optimized conditions, the recovery value was 94% with RSD 1.2%. The Limit of Detection (LOD) and Limit of Quantification (LOQ) were 1.22 and 3.69 mg/L, respectively. In our knowledge, it is the first time that this methodology is applied to analyze urinary catabolites of the polyphenol compound and to provide a specific method and simple analysis alternative. The selective extraction of these metabolites improves the application and results obtained by other less sensitive analysis methods than the validation method. It also facilitates the development of new screening methods.

Highlights

Diets rich in fruits and vegetables are related to positive effects on health and a lower risk of diseases [1]
protocatechuic acid (PCA) has been used as template for the synthesis of an Molecular imprinted polymers (MIP) for the extraction analogues compounds from plant in an Molecularly Imprinted Solid Phase Extraction (MISPE) procedure [13,14] or used as High-Performance Liquid Chromatography (HPLC)stationary phase to analyze synthetic samples of red wine [15,16]. 4-hydroxybenzoic acid (4-HBA)-MIP has been used in the stationary phase [16,19] and imprinting studies were carried out [17]
After remove of the template, binding sites remain that are capable of rebinding the template with high affinity and selectivity

Summary

Introduction

Diets rich in fruits and vegetables are related to positive effects on health and a lower risk of diseases (cardiovascular disorders, cancer, or neurodegeneration) [1]. Dietary phenolic compounds can be converted into smaller phenolic acid by microorganisms and may contribute to health benefits These benefit effects, previously related to the simple direct antioxidant hypothesis of an understanding of the complex effects on molecular targets and enzymes in specific cell types, have undergone and the importance of the microbiome is inherently integrated with flavonoid metabolism and bioactivity [1]. Molecular imprinted polymers (MIP) have attracted wide attention and attained significant applications in selective extraction of polyphenols compounds and hydroxylated metabolites in plants, natural products, foodstuffs, or biological and environmental samples. Only one work reported the application of MIP for the phenolic acid analysis in urine, but with a different purpose, the assessment exposure of toluene and xylenes [22]. Once the MISPE parameters were optimized, the procedure was validated using spiked human urine samples

Methods

Results

Conclusion