title: Cloud-point extraction and reversed-phase high performance liquid chromatography for analysis of phenolic compounds and their antioxidant activity in Thai local wines.
abstract: A cloud-point extraction (CPE) was developed for the determination of 12 phenolic compounds (i.e. gallic acid, procatechuic acid, p-hydroxybenzoic acid, vanillic acid, caffeic acid, syringic acid, p-coumaric acid, ferulic acid, guaiacol, p-cresol, o-cresol and 3,5-xylenol) using reversed-phase high performance liquid chromatography (RP-HPLC) with photodiode array (PDA) detection. The optimum CPE conditions were 2.0% (w/v) Triton X-114, 3.0% (w/v) Na2SO4 and 20-min equilibrated at 45 °C. The surfactant-rich phase was then analyzed by HPLC using a Symmetry C18 column, gradient mobile phase of acetonitrile and 1% (v/v) acetic acid, and PDA detection at 280 nm. Under the optimum condition, the target phenolic compounds were separated within 25 min. CPE gave higher enrichment factor up to 15-fold compared to that of direct analysis. The proposed method showed good analytical performances with limits of detection in the range 0.01-0.1 mg L(-1) and precisions with relative standard deviation (RSD) lower than 5% for retention time and 10% for peak area. The method was successfully applied to the analysis of phenolic compounds in Thai local wine samples. Gallic acid, procatechuic acid, and vanillic acid were the highest phenolics found in the studied wines with the contents up to 172.4, 99.1, and 26.6 mg L(-1), respectively. The recovery of the spiked wine samples (0.5, 1.0, and 2.0 mg L(-1)) were obtained in the range of 90.4-110%. High total phenolic content, total flavonoids, and antioxidant activity (DPPH method) in the studied wines were also observed.
authors.affiliation: Department of Chemistry and Center for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen, 40002 Thailand.
authors.forename: Jitlada
authors.initials: J
authors.lastname: Vichapong
authors.affiliation: Department of Chemistry, Faculty of Engineering, Rajamangala University of Technology Isan, Khon Kaen Campus, Khon Kaen, 40000 Thailand.
authors.forename: Yanawath
authors.initials: Y
authors.lastname: Santaladchaiyakit
authors.affiliation: Department of Chemistry and Center for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen, 40002 Thailand.
authors.forename: Rodjana
authors.initials: R
authors.lastname: Burakham
authors.affiliation: Department of Chemistry and Center for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen, 40002 Thailand.
authors.forename: Supalax
authors.initials: S
authors.lastname: Srijaranai
keywords: Antioxidant activity; Cloud-point extraction; High performance liquid chromatography; Phenolic compound; Thai local wine
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