Article pubs.acs.org/JAFC
Efficient Determination of Protocatechuic Acid in Fruit Juices by Selective and Rapid Magnetic Molecular Imprinted Solid Phase Extraction Coupled with HPLC Lianwu Xie,*,†,‡ Junfang Guo,‡ Yuping Zhang,‡ and Shuyun Shi*,‡ †
College of Sciences, Central South University of Forestry and Technology, Changsha 410004, People’s Republic of China College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, Poeple’s Republic of China
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ABSTRACT: Magnetic molecular imprinted polymers (MMIPs) have been prepared as solid phase material to selectively extract protocatechuic acid (PCA) from fruit juices with high capacity and fast binding kinetics. The resulting MMIPs were characterized by TEM, FT-IR, TGA, and VSM. The adsorption process between PCA and MMIPs followed Langumuir adsorption isotherm with maximum adsorption capacity at 7.5 mg/g and pseudo-second-order reaction kinetics with fast binding kinetics (equilibrium time at 40 min). In addition, the prepared MMIPs showed rapid magnetic separation (10 s) and reusability (retained 94.9% after six cycles). Subsequently, MMIPs were successfully applied for selective enrichment and determination of PCA from fruit juices (0.45 μg/mL in grape juice but not detected in apple juice, pineapple juice, orange juice, and peach juice) with satisfactory recoveries (92−107%). The results indicated that synthesized MMIPs can be used for efficient and selective extraction of PCA from complex matrices. KEYWORDS: protocatechuic acid, fruit juice, molecular imprinted polymer, magnetic solid phase extraction, HPLC analysis
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INTRODUCTION Protocatechuic acid (PCA), a phenolic compound, is widely distributed in commonly consumed foods, fruits, juices, and traditional Chinese medicine. At the same time, PCA is the major human metabolite of cyanidin-glucosides, flavonoids widely existing in fruit.1,2 Pharmaceutical investigations indicate that PCA exhibits a wide variety of bioactivities, such as strong antioxidant,3 wide anticancer,4,5 anti-inflammatory,6 and anticarcinogenic7 properties. Moreover, PCA has been studied in ongoing clinical trials.8 Nowadays, PCA has attracted increasing interest as a dietary supplement in an expanding health food market. However, the qualitative and quantitative analyses of polar PCA in a complex matrix (e.g., fruit juice, food, natural product, and biological sample) are difficult because of the low concentration of PCA (e.g., 1, which showed a higher binding selectivity of MMIPs than MNIPs for PCA than other tested similar compounds. However, in our previously prepared MMIPs using benzoic acid/4-HBA as template, the K′ values (K′ = KMMIPs/KMNIPs, K′ = Kd(template)/Kd(PCA)) for PCA were
