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Biomedical subjects

X M Liang

Publications and source records attributed to X M Liang.

At least 19 recordsLinked to original sources
PubMed2005

Predicting gas chromatographic retention times of 209 polybrominated diphenyls (PBBs) for different temperature programs.

A method has been developed to predict the retention times of 209 individual polybrominated diphenyl congeners for different temperature programs. The retention equations lnk'=A+B/T of five PBBs in gas chromatography (GC) were used to evaluate the properties of the regression coefficients A and B, which are widely accepted as being highly reliable chromatographic retentions. The quantitative relationships between the A and B values of PCBs and those of PBBs were found. The regression equations derived have coefficients of determination greater than 0.999. The A, B values of any PBB can be predicted by using the A, B values of the PCB according to these relationships. Using these predicted A and B values, the retention times of all PBBs can be predicted. This is an important advance in the identification of PBBs because at present there are only a few PBB standards available.

Chromatography, Gas↗
PubMed2005

In vitro estrogenic activities of Chinese medicinal plants traditionally used for the management of menopausal symptoms.

The estrogenic activity of 70% EtOH extracts of 32 traditional Chinese medicinal plants, selected according to their reported efficacy for the treatment of menopausal symptoms, was assessed using a recombinant yeast system with both a human estrogen receptor expression plasmid and a reporter plasmid. Among them, 11 (34%) species proved to be active. Polygonum cuspidatum had the highest estrogenic relative potency (RP) (3.28 x 10(-3)), followed by Rheumpalmatum (3.85 x 10(-4)), Cassia obtusifolia (3.49 x 10(-4)), Polygonum multiflorum (2.87 x 10(-4)), Epimedium brevicornum (2.30 x 10(-4)), Psoralea corylifolia (1.90 x 10(-4)), Cynomorium songaricum (1.78 x 10(-4)), Belamcanda chinensis (1.26 x 10(-4)), Scutellaria baicalensis (8.77 x 10(-5)), Astragalus membranaceus (8.47 x 10(-5)) and Pueraria lobata (6.17 x 10(-5)). The EC(50) value of 17beta-estradiol used as the positive control was 0.205+/-0.025 ng/ml (RP=100). This study gave support to the reported efficacy of Chinese medicines used for hormone replacement therapy.

Female↗
PubMed2004

Determination and identification of isoflavonoids in Radix astragali by matrix solid-phase dispersion extraction and high-performance liquid chromatography with photodiode array and mass spectrometric detection.

The isoflavonoids in Radix astragali were determined and identified by HPLC-photodiode array detection-MS after extraction employing matrix solid-phase dispersion (MSPD). As a new sample preparation method for R. astragali, the MSPD procedure was optimized, validated and compared with conventional methods including ultrasonic and Soxhlet extraction. The amounts of two major components in this herb, formononetin (6) and ononin (2), were determined based on their authentic standards. Four major isoflavonoids, formononetin (6), ononin (2), calycosin (5) and its glycoside (1), and three minor isoflavonoids, (6aR,11aR)-3-hydroxy-9, 10-dimethoxypterocarpan (7), its glycoside (3), and (3R)-7,2'-dihydroxy-3',4'-dimethoxyisoflavone-7-O-beta-D-glycoside (4), were identified based on their characteristic two-band UV spectra and [M + H], [aglycone + H]+ and [A1 + H]+ ions, etc. The combined MSPD and HPLC-DAD-MS method was suitable for quantitative and qualitative determination of the isoflavonoids in R. astragali.

Astragalus Plant↗
PubMed2003

Complete sequence of the genomic RNA of the prevalent strain of a potyvirus infecting maize in China.

The complete nucleotide sequence of the prevalent strain of a potyvirus isolated from maize in Beijing, China was determined and compared with other closely related potyviruses. The viral genome comprises 9595 nucleotides, excluding the poly (A) tail, and encodes a putative polyprotein of 3063 amino acid residues. Sequence comparison of the coat proteins showed that this isolate was most closely related to most other potyviral isolates infecting maize across China with identities of about 99% and thus represented the prevalent strain. It was also closely related to most isolates of Sugarcane mosaic virus (SCMV) infecting maize in Europe with maximum identity of about 95% at the amino acid level. The polyprotein sequence of the Beijing isolate shares identities of 98% with those of two other Chinese maize isolates and shares identity of 69% with Maize dwarf mosaic virus-Bulgarian isolate, respectively. Phylogenetic analyses of the sequences indicated that the Beijing isolate can be tentatively referred to as a prevalent strain of SCMV.

Binding Sites↗
PubMed2002

Computer-assisted automatic peak recognition and result evaluation for analysis of chlorinated hydrocarbons in environmental samples.

A data manipulation method has been developed for automatic peak recognition and result evaluation in the analysis of organic chlorinated hydrocarbons with dual-column gas chromatography. Based on the retention times of two internal standards, pentachlorotoluene and decachlorobiphenyl, the retention times of chlorinated hydrocarbons can be calibrated automatically and accurately. It is very convenient to identify the peaks by comparing the retention times of samples with the calibrated retention times calculated from the relative retention indices of standards. Meanwhile, with a suggested two-step evaluation method the evaluation coefficients and the suitable quantitative results of each component can be automatically achieved for practical samples in an analytical system using two columns with different polarities and two internal standards.

Automation↗
PubMed2001

The use of brush cytology and directed biopsies for the detection of nasopharyngeal carcinoma and precursor lesions.

BACKGROUND: It has been proposed that nasopharyngeal carcinoma (NPC) has an early noninvasive stage, designated nasopharyngeal intraepithelial neoplasia (NPIN). Hence, the detection and treatment of NPIN will prevent NPC from developing, and this would be similar to the strategies used for cervical cancer prevention. We wanted to ascertain the feasibility of using a brush sampler to collect cells for the cytologic diagnosis of NPIN and NPC. If successful, the technique could be used as a screening test in endemic areas. METHODS: A disposable sampler (Uterobrush) was used to collect nasopharyngeal mucosal brushings from 546 patients for cytologic examination. After this, most patients had biopsies, and this allowed histologic-cytologic correlation to be undertaken. RESULTS: In 528 patients (96.7%) there were satisfactory cytologic and biopsy specimens for evaluation. There were 149 cases with positive histology and 103 had positive cytology (specificity was 100% and the sensitivity was 69.1%). One case of NPC with concurrent NPIN was seen among the biopsy specimens, but no case of NPIN was detected cytologically. CONCLUSIONS: The cytologic pickup of NPC was substantially lower than that obtained on biopsy. More importantly, NPIN was uncommon. Therefore, a screening test that depends on the collection of cells for the microscopic diagnosis of NPIN and NPC is unlikely to have a major impact on the incidence of NPC. Furthermore, obtaining a good cytologic specimen from the nasopharynx is not simple, and this further limits this technique for mass screening purposes. The concept of a cytologic test for NPC, similar to the Pap test for the prevention of uterine cervix cancer, has still to be realized.

Adult↗
PubMed2001

[Recognition and quantitative contrast characteristic components for root of Chinese angelica].

A method of multi-component quantitative analysis in root of Chinese Angelica has been developed. The analytical mode was reversed-phase HPLC with photodiode array detector. Based on comparison of UV spectra, a software of UV spectra database to assist recognition has been established. The solvent system, a gradient program of mobile phase with 2-propanol/acetonitrile/water can separate a lot of liposoluble components in root of Chinese Angelica. UV detection wavelength was set at 202 nm and the flow rate was 1 mL/min on a Hypersil ODS column. Twenty-three components in two roots of Chinese Angelica were recognized using characteristic parameters of chromatography and UV spectroscopy. It is the base of quantitative contrast to recognize many characteristic components without standard components in root of Chinese Angelica. For two samples of root of Chinese Angelica both have 23 characteristic components and the concentrations of some components were similar and those of others were different. The method is convenient and reproducible. It can be used for the quality control of the root of Chinese Angelica without the use of standards.

Angelica sinensis↗
PubMed2001

[Advances in estimation of physico-chemical parameters of organic compounds by RP-HPLC].

Reversed-phase high performance liquid chromatography is currently used in the determination of some important physico-chemical properties of compounds, and its potential uses in areas of modeling environmental behaviour and pharmacological activity of compounds are desirable. This paper reviews the methodology, major areas, present situation and chief difficulties of RP-HPLC method for the estimation of physico-chemical parameters, and the perspective of this method.

Chemical Phenomena↗
PubMed2001

[Study of unified analytical method of compatibleness for traditional Chinese medicines. I. Separation, recognition of characteristic components and fingerprint analysis for single and complex medicines].

It is difficult to separate, identify and quantify multi-component in complex traditional Chinese medicines (TCM). Many analytical methods for TCM have been established, but only a few components can be separated and quantified. For analyzing the multi-component and finding new method of compatibility analysis, a strategy--the multi-mode and multi-column chromatographic system and unified analytical method has been proposed by us. A part of the results from the study of astragalus root(A), Chinese angelica root(Ca.) and their complex prescription (Danggui Buxue Tang, DBT) with the analytical mode of reversed-phase HPLC/photodiode array detector as an example of the method for unified separation and recognition of characteristic components and fingerprint analysis was introduced. This is the first part of the results of compatibleness analysis for TCM.

Angelica sinensis↗
PubMed2001

[Determination of impurities in a technical chlorpyrifos by gas chromatography with atomic emission detection].

Mass fraction of impurities in a technical chlorpyrifos sample may be obtained by selective determination on carbon (496 nm and 193 nm), chlorine(479 nm), and sulfur (181 nm) channels using gas chromatography with atomic emission detection(GC/AED). According to the formulas from GC/MS and analytical results from GC/AED, mass fraction of compounds may be calculated by internal standard of elements. The results for the same compound obtained from different elemental channels were consistent. This shows the responses of carbon, chlorine and sulfur on AED are independent on molecular structures. Moreover, the reliability of the qualitative results of impurities from GC/MS was proved. If the formulas from GC/MS were wrong, the results from different elemental channels on GC/AED would be different. The relative deviations were in the range of -3.4% to 5.8%. When standards are not available, the results from GC/AED are more reliable than those from GC/FID which usually depend on the area normalization without corrections. Pesticides and other complex organic mixtures may be analyzed reliably and expediently by this method.

Chlorpyrifos↗
PubMed2001

[Study of unified analytical method of compatibleness for traditional Chinese medicines. II. The quantitation of curve fitting].

To introduce method of compatibleness analysis for traditional Chinese medicines, we select a part of the results from the study of astragalus root(A.), Chinese angelica root(Ca.) and their complex prescription (Danggui Buxue Tang, DBT) with an analytical mode of reversed-phase HPLC-photodiode array detector as an example of the quantitation of curve fitting. A new quantitative method, the concentration variation of components as the changing of single prescription dosage in complex prescriptions is discussed. This is the second part of the method of compatibleness analysis for traditional Chinese medicines.

Angelica sinensis↗
PubMed2001

[Characterization and recognition key components in Astragalus membranaceus].

AIM: To separate, identify and quantify multi-components in complex traditional Chinese medicine (TCM) Astragalus membranaceus by unified analysis for systematic study of its relative contents. METHODS: The analytical method was reverse-phase HPLC/photodiode array detector. Based on the comparison of UV spectra, software of UV database to assist recognition has been established. Key components have been found and recognized in two reference Astragalus membranaceus and three samples from different sources. With the unified analytical project, relative peak heights of key components were recognized and contrasted. RESULTS: The water-soluble components can be separated by solvent system A, a gradient program with mobile phase of methanol-water. The liposoluble components can be separated with the solvent system B, a gradient program of mobile phase of 2-propanol-acetonitrile-water. UV detection wavelength was set at 202 nm and the flow rate was 1 mL.min-1 on a Hypersil ODS column. Twenty-nine components in the four Astragalus membranaceus were recognized using characteristic parameters of chromatography and UV spectroscopy. All of the 29 key components in two reference samples and three samples from different sources were shown in their chromatograms to be the same. The concentrations of some the key components in different samples were similar while those of the others were different. The chromatographic peaks of the reference Astragalus membranaceus and two samples were matched with each other. Many different fingerprints were found and differences were shown on their chromatograms. Not only there were differences among three samples from different source, but also there were differences in the two reference samples. CONCLUSION: To find out the key components and recognize them are the basis of quantitative recognition and are very useful when standards are not available. The method of multi-component quantitative recognition in Astragalus membranaceus was developed. The method is convenient and reproducible. It can be widely used for the quality control of the Astragalus membranaceus.

Astragalus propinquus↗
PubMed2000

[Influence of organic modifier on the retention behaviour in soil leaching column chromatography].

The relationship between capacity factors (k') of 55 nonionic compounds and broad methanol volume percentage (psi) of methanol-water eluent in soil leaching column chromatography (SLCC) was systematically investigated. The compounds consist of 11 chlorobenzenes, 14 alkylbenzenes, 22 polyphenyls and polycyclic aromatic hydrocarbons, and 8 pesticides. Reference soil was dry-packed into a stainless steel chromatographic column (10 mm i.d. x 100 mm) by a homemade pressurizing device, and isocratic methanolwater mixture with psi from 0.0 to 0.80 eluated through the column at a flow-rate of 1 mL.min-1. The column was thermostated at (25.0 +/- 0.1) degree C, and chromatographic peak was monitored by an online ultraviolet detector. The results show that both equations, log k' = log k'w + a psi + b psi 2(1) and log k' = log k'w - S psi (2), well fit the retention values. Equation (2) can be used practically due to few experimental data needed and simpler in formula. Explanation is also given for the existence of the carbon (or chlorine) number rule for two classes of homologous series (i.e. methylbenzenes, n-alkylbenzenes) and weak-polar chlorobenzenes in the SLCC process. The slope and intercept of the rule are also well correlated, and both decreases linearly with increasing eluent psi value.

Chlorobenzenes↗
PubMed2000

[Selectivity of poly (4-methyl-5-vinylthiazole) stationary phase in reversed-phase liquid chromatography].

In this paper, the selectivity of poly(4-methyl-5-vinylthiazole) stationary phase (PMV CA phase) is comprehensively studied in reversed-phase liquid chromatography (RPLC) mode with methanol-water system. The selectivity difference between PMV CA phase and three commonly used RPLC stationary phases (C18, C8 and Phenyl phase) is shown. Four typical species of standards (alkylbenzens, chlorobenzenes, nitrobenzenes and PAHs) are selected for the selectivity study. It is shown that the PMV CA phase has some special selectivities: 1) It has different selectivity from C18 and C8 phase because the PMV CA phase may form diploe interaction, pi-electron interaction and hydrogen bonding interaction (with the nitrogen atom and oxygen atom on the phase) with solutes owing to its polar aromatic thiazole ring and polar ester bond etc. on the phase; 2) It has similar property as phenyl phase because both of them can form pi-electron interaction with solutes. But owing to its polar thiazole ring and other polar group on the phase, which may form dipole interaction and hydrogen bonding interaction with solutes, there are still some differences between these two phases.

Benzo(a)pyrene↗
PubMed2000

[Application of the quantitation with curve-fitting method on chiral separation by high performance liquid chromatography].

We propose for the first time that curve-fitting method should be applied to the quantitation of overlapping peaks in chiral separation by high performance liquid chromatography (HPLC). We have examined the separation of eight isomers of cyfluthrin on a chiral stationary phase (CSP), and found that in comparing with the perpendicular-drop method, the accuracy of quantitation of overlapping peaks with curve-fitting was much higher. Generally, errors in peak area measurement using the perpendicular-drop method become larger as the degree of peak overlap increases. Meanwhile, by using curve-fitting method errors have no apparent difference for different degrees of peak overlap. Generally, for the same chiral compounds, although the resolutions are different with different mobile phase strength, the results of peak areas are the same by using curve-fitting method.

Chromatography, High Pressure Liquid↗
PubMed2000

[Analysis of ginsenosides by high performance liquid chromatography/mass spectrometry/mass spectrometry(LC/MS/MS)].

Ginseng, one of the most popular medicinal herbs used in traditional Chinese medicines, has been studied to have biological effects attributing to its main constituents such as ginsenosides. There are more than 30 kinds of ginsenosides and some of them have similar polarity and structure. Thus, it is difficult to separate those ginsenosides with isocratic mobile phase owing to their similar polarity. A reversed-phase high performance liquid chromatographic method with gradient elution has been developed in this work. Nine ginsenosides can be separated by this method. Among them, five ginsenosides with different molecular weights can be determined by means of their molecular weight gained through LC/MS with an ESI interface. Re and Rd have the same Mw but belonging to two different kinds of ginsenosides. They can be differentiated from each other through their MS/MS gained by CID(collision induced decomposition) at the second stage quadrapole. Rc and Rb3 having the same molecular weight and belonging to the same kind of ginsenoside can be distinguished through their negative ion spectra gotten from LC/MS. So 9 ginsenosides can be determined by LC/MS/MS. This method can also be used to determine the ginsenosides contained in commercially available samples.

Chromatography, High Pressure Liquid↗
PubMed2000

[Simultaneous determination of sulbactam sodium and cefoperazone sodium in sulperazon by high performance liquid chromatography].

A reversed-phase, isocratic high performance liquid chromatographic method with acid mobile phase can separate sulbactam and cafoperazone within 12 minutes. Column packed with Hypersil ODS2(250 mm x 4.6 mm i.d., 5 microns) was manufactured by Dalian Elite Company. Mobile phase is composed of water (adjusted to pH 4.0 with 1% phosphoric acid) and acetonitrile (80:20, V/V). The detection was performed at 210 nm and the injection volume was 2 microL. Cefoperazone and sulbactam have good linearity in the ranges of 100 mg/L to 800 mg/L and 100 mg/L to 1,000 mg/L with the correlation coefficients of 0.9991 and 0.9997 respectively. This method is easily to be operated and can be applied for manufacturing and medicinal study.

Anti-Infective Agents, Urinary↗