title: Simultaneous extraction and determination of free and conjugated phytosterols in tobacco.
abstract: Acid hydrolysis and alkaline saponification were incorporated into a microwave-assisted extraction process for the simultaneous extraction of free and conjugated phytosterols from tobacco. The crude extract of the microwave-assisted extraction was purified by C18 solid-phase extraction and then determined by high-performance liquid chromatography. Phytosterols of cholesterol, ergosterol, stigmasterol, campesterol, and β-sitosterol were determined by chromatographic quantification. The multiple parameters of microwave-assisted extraction were optimized by a uniform design method. The optimal ratio of extraction ethanol solvent to tobacco mass was 30 mL/g. The microwave-assisted extraction acid hydrolysis was carried out in sulfuric acid medium by heating for 10 min at 55°C. The microwave-assisted extraction alkaline saponification was performed after adding excessive sodium hydroxide by heating another 10 min. The repeatability of the proposed method was acceptable with recoveries from 69.68 to 88.17% for the phytosterols. Five target phytosterols were all found in the tobacco samples, and the contents were significantly different in samples from different producing areas.
authors.affiliation: Beijing Key Laboratory of Microanalysis Methods and Instrumentation, Department of Chemistry, Tsinghua University, Beijing, PR China.|Institute of Food and Fermentation Industries, Fuqing Branch of Fujian Normal University, Fuqing, PR China.
authors.forename: Lei-Wen
authors.initials: LW
authors.lastname: Xiang
authors.affiliation: Beijing Engineering Research Center of Food Safety Analysis, Beijing Center for Physical and Chemical Analysis, Beijing, PR China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Beijing Key Laboratory of Microanalysis Methods and Instrumentation, Department of Chemistry, Tsinghua University, Beijing, PR China.
authors.forename: Hai-Fang
authors.initials: HF
authors.lastname: Li
authors.affiliation: Beijing Key Laboratory of Microanalysis Methods and Instrumentation, Department of Chemistry, Tsinghua University, Beijing, PR China.
authors.forename: Jin-Ming
authors.initials: JM
authors.lastname: Lin
mesh_terms: D002851:Chromatography, High Pressure Liquid; D010840:Phytosterols / Q000032:analysis*; D052616:Solid Phase Extraction; D014026:Nicotiana / Q000737:chemistry*
chemical_list: D010840:Phytosterols
keywords: High-performance liquid chromatography; Microwave-assisted extraction; Phytosterols; Solid-phase extraction; Tobacco