Yi-Qun Wan

Simultaneous determination of organophosphorus pesticides in Chinese herbal medicines by microwave-assisted extraction coupled with dispersive-solid phase extraction and gas chromatography.

A reliable, rapid and nontoxic analytical method was proposed for the simultaneous determination of 16 organophosphorus pesticides in Chinese herbal medicines. The pesticides were extracted by ethanol and the experimental variables, such as temperature, extraction time and volume of ethanol, were optimized through orthogonal array experimental design. Cleanup of extracts was performed with dispersive-solid phase extraction using primary secondary amine as the sorbent. The determination of pesticides in the final extracts was carried out by gas chromatography-flame photometric detection. Under optimized conditions the obtained recoveries, except for isocarbophos, were in the range 73.8-123%, with relative standard deviations equal to or lower than 15.2% and limits of detection ranging from 0.001 to 0.009 mg/kg.

Simultaneous determination of three potential cancer biomarkers in rat urine by synchronous fluorescence spectroscopy

A rapid, simple, sensitive and accurate method for the simultaneous determination of three potential cancer biomarkers [tryptophan (TRP), isoxanthopterin (ISO) and xanthopterin (XAN)] in rat urine with synchronous fluorescence spectroscopy has been developed. In order to eliminate the interference in urine samples, the synchronous fluorescence spectra were obtained with Δλ=70 nm in a KH2PO4-NaOH buffer solution (pH=8.0). The detected wavelengths of quantitative analysis were set at 275 nm for TRP, 325 nm for ISO and 400 nm for XAN, respectively. Under the optimized conditions, the limits of the detection of the three compounds were 2.73 ng/mL, 0.52 ng/mL and 0.94 ng/mL, respectively. The recoveries were in the range of 80.5-98.0%, with the coefficient of variation between 0.62% and 2.48%. The proposed method has been applied to the simultaneous determination of TRP, ISO and XAN in rat urines of bladder cancer group and control group. The determination results showed that the average level of TRP, ISO and XAN had different change trends with the growth of the tumor. The three analytes could be used as potential biomarkers for noninvasive diagnosis of different stage of bladder cancer. However, more data are needed to support this hypothesis.

Fractionation, physicochemical property and immunological activity of polysaccharides from Cassia obtusifolia.

The seeds of Cassia obtusifolia are widely used as a drink in Asia and an additive in food industry. Considerable amounts of water-soluble polysaccharides were found in the whole seeds, while conflicting results on structure characteristics have been reported, and few studies have been reported on physicochemical properties and immunomodulatory activities. In the present study, gradient ethanol precipitation was applied to fractionate the water-soluble polysaccharide (CP), and two sub-fractions CP-30 (30% ethanol precipitate) and CP-40 (40% ethanol precipitate) were obtained. Different rheological properties for CP-30 and CP-40 were found, indicating the differences in structure characteristics between CP-30 and CP-40. Chemical properties, including molecular weight, monosaccharide composition, and glycosidic linkage were investigated. Compared with CP-30, CP-40 had lower molecular weight and higher content of xylose. The immunomodulatory effects of CP, CP-30 and CP-40 were assessed. All of them were found to possess significant immunomodulation activities, while varied effects of them on macrophage functions were observed. The aim of the present study was to develop a simple and efficient method to purify cassia polysaccharides, and investigate their physicochemical properties and biological activities, which was meaningful for their potential use in food industry and folk medicine.

Determination of Organotin Compounds in Wine by Microwave-Assisted Extraction and High Performance Liquid Chromatography–Inductively Coupled Plasma Mass Spectrometry

A new analytical procedure for the determination of five organotin compounds in several matrix wine samples is reported. The organotin compounds were extracted by microwave-assisted extraction with n-hexane. Extraction conditions, such as volume of n-hexane required, extraction temperature, and extraction time, were investigated and optimized by an orthogonal array experimental design. The determination of organotin compounds in the final extracts was carried out by liquid chromatography–inductively coupled plasma mass spectrometry. The procedure showed limits of detection between 0.029–0.049 µg · L−1. The linearity was in the range of 0.5 to 100 µg · L−1. The precision expressed as relative standard deviation (RSD) was below 9.43%. The developed method was successfully employed to analyze different matrix wine samples, and some analytes were detected at the level of 0.053 to 1.14 µg · L−1.

DISCRIMINATION OF DIFFERENT GANODERMA SPECIES AND THEIR REGION BASED ON GC-MS PROFILES OF STEROLS AND PATTERN RECOGNITION TECHNIQUES

A GC-MS method based on the profiling of sterol peaks has been applied first for the discrimination of different Ganoderma species and their region. Six common sterol peaks were found and identified to be the discriminant variables. Pattern recognition analyses such as hierarchical cluster analysis (HCA) and discriminant analysis (DA) were used to deal with the data set of sterol profiles, and the results showed that there are definite differences among the different Ganoderma samples. This could provide another approach for the classification of Ganoderma samples in addition to conventional methods based on the profiling of triterpenoids and polysaccharides.

Simultaneous Determination of Organotin Compounds in White Wine by Gas Chromatography-Mass Spectrometry

A simple, reliable, and effective analytical method was developed for the simultaneous determination of five organotin compounds (OTCs) including monobutyltin trichloride dibutyltin dichloride tributyltin chloride tetrabutyltin and triphenyltin chloride in white wines. The OTCs were derivatized with sodium tetraethylborate (NaBEt4), and their derivatives were extracted by liquid-liquid extraction (LLE) into n-hexane. The experimental variables, such as type and volume of extraction solvents, amount of derivatization reagent NaBEt4 and extraction time were optimized. The determination of ethylated derivatives of OTCs in the final extracts was carried out by gas chromatography-mass spectrometry (GC-MS). Under optimized conditions, good linearity was observed when analytical concentrations were in the range of 0.01–4.0 µg · mL−1, the linearity correlation coefficients were between 0.9982 and 0.9987, with the LODs in the range of 0.2–3.0 µg · L−1, and the LOQs varied from 0.6 to 10.0 µg · L−1. The obtained recoveries were in the range of 78.0–120.0%, with the relative standard deviations equal to or lower than 8.1%. This method was applied to the determination of OTCs in white wines with satisfactory results.

Determination of Tyrosine and Its Metabolites in Human Serum with Application to Cancer Diagnosis

A simple, rapid, and economical method is reported for the determination of 3,4-dihydroxyphenylalanine, tyrosine, 4-hydroxyphenyllactic acid, 4-hydroxyphenylacetic acid, 4-hydroxyphenethylamine, and 3-(4-hydroxyphenyl)propionic acid in human serum by ultra-performance liquid chromatography coupled with fluorescence detection. Separation was achieved on a C18 column with isocratic elution using 95:5 (v/v) 50 mM ammonium formate buffer at pH 5.8 and acetonitrile. Fluorescence detection was performed with excitation and emission wavelengths of 277 and 316 nm, respectively. Under the optimized conditions, all compounds were eluted within 10 min. The effectiveness of various protein precipitants was investigated for the pretreatment of serum samples and 5% perchloric acid was selected as optimal. The calibration curves were linear (correlation coefficients > 0.9996), and the limits of detection and quantification for tyrosine and its metabolites ranged from 0.016 to 0.032 mg/L and 0.040 to 0.080 mg/L, respectively. Recoveries of tyrosine and its metabolites in normal subjects and cancer patients were in the range of 86.5–102.5% and 88.3–107.3%, respectively, with RSDS of 0.3–5.7% and 0.5–4.3%. Significant differences in serum concentrations of tyrosine and 4-hydroxyphenyllactic acid were found between normal individuals and cancer patients.

Enzymatic purification and structure characterization of glucuronoxylan from water extract of Cassia obtusifolia seeds

Enzymatic hydrolysis was proposed for the first time to purify the sub-fraction of water-extracted cassia polysaccharide (CP-40), and a homogeneous polysaccharide CP-40-M was obtained with relatively high yield. The structural features of CP-40-M were characterized using size-exclusion chromatography equipped with multiple detectors (SEC-MALLS), high-performance anion-exchange chromatography (HPAEC), methylation and gas chromatography-mass (GC-MS), as well as nuclear magnetic resonance (NMR) spectra. The weight-average molecular weight for CP-40-M was determined to be 0.29×105Da, and the molar ratio of xylose to glucuronic acid was 4.62. The structure of CP-40-M was elucidated to be glucuronoxylan, with glucopyranosyluronic acid group terminally attached to O-2 of the →4)-β-Xylp-(1→ backbone. It was the first time to obtain this type of xylan from the water extract of Cassia obtusifolia seeds. The structure elucidation of CP-40-M was meaningful for better understanding the natural characteristics of cassia polysaccharide and important for their potential use in food industry and folk medicine.