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Pang-Chui Shaw

Publications and source records attributed to Pang-Chui Shaw.

At least 19 recordsLinked to original sources
PubMed2007

Molecular authentication of Radix Puerariae Lobatae and Radix Puerariae Thomsonii by ITS and 5S rRNA spacer sequencing.

In the present study, we examined nuclear DNA sequences in an attempt to reveal the relationships between Pueraria lobata (Willd). Ohwi, P. thomsonii Benth., and P. montana (Lour.) Merr. We found that internal transcribed spacer (ITS) sequences of nuclear ribosomal DNA are highly divergent in P. lobata and P. thomsonii, and four types of ITS with different length are found in the two species. On the other hand, DNA sequences of 5S rRNA gene spacer are highly conserved across multiple copies in P. lobata and P. thomsonii, they could be used to identify P. lobata, P. thomsonii, and P. montana of this complex, and may serve as a useful tool in medical authentication of Radix Puerariae Lobatae and Radix Puerariae Thomsonii.

DNA, Plant↗
PubMed2006

Antitussive effects of Stemona tuberosa with different chemical profiles.

The root tubers of Stemona tuberosa, Stemona japonica and Stemona sessilifolia are recognized by the Pharmacopoeia of the People's Republic of China as authentic sources of the herb Radix Stemonae (Baibu). Careful anatomical analyses of these three species, whose identities were confirmed by flowering and fruiting samples, revealed that the root tubers of Stemona tuberosa could be distinguished from those of the other two species by the presence of scattered fibers in the cortex and pith and by the absence of thickened striations on the surface of velamen cells. HPLC analyses demonstrated that the total alkaloid profiles could be grouped into four types represented as the major component by stenine-type Stemona alkaloids such as tuberostemonine (4) and neotuberostemonine (3), or by non-stenine types such as croomine (1) and stemoninine (2). Nevertheless, all these samples demonstrated different degrees of antitussive properties in guinea pigs. These results suggested that non-stenine-type of Stemona alkaloids also contributed to the antitussive properties. The variations in chemical profiles among herb samples add difficulty in ensuring quality control in botanical products.

Alkaloids↗
PubMed2006

Analyses of Stemona alkaloids in Stemona tuberosa by liquid chromatography/tandem mass spectrometry.

Alkaloid profiles in Stemona tuberosa were found to be highly variable. Six Stemona alkaloids isolated from the plant were subjected to on-line high-performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS) and tandem mass spectrometry (MS/MS) analyses. Their fragmentation patterns and products were useful for their characterization. The LC/MS fingerprints of these alkaloids, though variable among samples, could provide an overall characterization of the authenticity and quality of this species and help to differentiate it from S. japonica and S. sessilifolia, as all three species are recognized as genuine sources of the herb Radix Stemonae in the Pharmacopoeia of the People's Republic of China.

Alkaloids↗
PubMed2006

Quantitative analyses of indoloquinazoline alkaloids in Fructus Evodiae by high-performance liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry.

Fructus Evodiae (Wuzhuyu), the fruits of Evodia rutaecarpa and related varieties, is widely used in traditional Chinese medicine. The bioactive constituents include the indoloquinazoline alkaloids rutaecarpine, evodiamine and dehydroevodiamine. A new assay based on high-performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry (HPLC/UV/APCI-MS/MS) was developed for the measurement of the indoloquinazoline alkaloids in commercial Fructus Evodiae products. Initially, the MS/MS fragmentation pathways of indoloquinazoline alkaloids were investigated to identify fragment ions that might be useful for the sensitive and selective detection of trace indoloquinazoline alkaloids during LC/MS/MS. Then, quantitative MS analysis of five indoloquinazoline alkaloids in 12 commercial Fructus Evodiae products from different geographical sources was performed. Analyte recovery was in the range of 97.5-105.3% for all with relative standard deviations (RSDs) below 6%, the intra-assay and inter-assay RSDs were less than 7%, and good linear relationships were shown with correlation coefficients for the analytes exceeding 0.999. Therefore, this LC/MS/MS assay facilitated the rapid quantitative analysis of rutaecarpine, evodiamine, evodiamide, 14-formyldihydrorutaecarpine and dehydroevodiamine in 12 commercial Fructus Evodiae products with excellent recovery, repeatability, accuracy and sensitivity. This method is simple and specific and can be used for identification and quality control of this traditional Chinese remedy.

Chromatography, High Pressure Liquid↗
PubMed2006

Alkaloids and chemical diversity of Stemona tuberosa.

Phytochemical investigation of the chemical components of Stemona tuberosa led to the isolation of two new alkaloids named tuberostemonine K (1) and tuberospironine (2), together with the known tuberostemonine (3). The new structures of 1 and 2 were elucidated through extensive spectroscopic analyses, while the molecular structure of 3 was confirmed by X-ray analysis. A gradient reversed-phase HPLC-ELSD method was established for the investigation of the chemical diversity of S. tuberosa from 13 localities, and four types of chemical variation featured by the major components 3, neotuberostemonine (4), croomine (5), and stemoninine (6), respectively, were observed.

Alkaloids↗
PubMed2006

Functional studies of the small subunit of EcoHK31I DNA methyltransferase.

EcoHK31I DNA methyltransferase recognizes the sequence 5'-YGGCCR-3' and adds a methyl group to the fifth position of the internal cytosine to protect the DNA from cleavage by its cognate endonuclease. M.EcoHK31I is composed of polypeptides alpha and beta. Polypeptide beta only contains the conserved IX motif of the C5-MTase family, and provides a unique example to show that this motif alone may be dislocated to another polypeptide. By electromobility shift assay, we found that the alpha/beta complex recognizes specific oligonucleotide substrates. Polypeptide alpha formed aggregates with DNA, while polypeptide beta alone did not bind DNA. Therefore, polypeptide beta assists in the proper binding of polypeptide alpha to DNA substrate. The complex of polypeptide alpha and a polypeptide beta variant with an N-terminal deletion of 41 amino acids showed a 16-fold reduction in methylation activity. Further deletion resulted in an inactive methyltransferase. The dissociation equilibrium constant (Kd) of the alpha/beta complex was 56.4 nM, while the Kd value for the alpha/deltaN46-polypeptide beta complex was increased approximately 95-fold, caused by a drastic decrease in dissociate rate constant (kd) and an increase in the association rate constant (ka). This indicates that the N-terminal region of polypeptide beta takes part in subunit interaction, while the C-terminal region is involved in DNA binding.

Base Sequence↗
PubMed2005

Isolation and chemotaxonomic significance of tuberostemospironine-type alkaloids from Stemona tuberosa.

An alkaloid named 6alpha-hydroxycroomine (1) as well as the known croomine (2), both belonging to the tuberostemospironine-alkaloid type, were isolated from Stemona tuberosa as the major components. The structure of 1 was elucidated through extensive spectroscopic analyses. Comparison of the HPLC profiles of the total alkaloids and the crude methanol extract showed that both compounds are naturally occurring. The first isolation of 1 and 2 from S. tuberosa has chemotaxonomic significance, confirming the close relationship between Stemona and Croomia. The trnL sequences of plants from the four genera of Stemonaceae cluster together as a clade, further lending support to retaining them in a single family.

Alkaloids↗
PubMed2005

Isolation of iridoid and secoiridoid glycosides and comparative study on Radix gentianae and related adulterants by HPLC analysis.

HPLC profile guided study led to the isolation of an acylated secoiridoid glycoside, named gentiotrifloroside (1), together with six known compounds, i.e., loganic acid (2), 6-O-beta-d-glucopyranosylgentiopicroside (3), swertiamarin (4), gentiopicroside (5), sweroside (6) and 2 -(o,m-dihydroxybenzyl)-sweroside (7) from Gentiana triflora and Gentiana rigescens. The structure of 1 was deduced from one- and two-dimensional NMR spectroscopic experiments. Compounds 1-7 were used successfully as chemical markers for the comparison of the four species of Gentiana used as Radix gentianae. Additionally, differentiation of Gentiana species mentioned and those used as adulterants was evaluated. The close similarity of chemical composition among the four genuine Gentiana species explain their popular usage as R. gentianae in Chinese medicine. We have also shown that the variation of chemical composition in R. gentianae and related adulterants agree well with their botanical phylogeny.

Animals↗
PubMed2005

Authentication and quantitative analysis on the chemical profile of cassia bark (cortex cinnamomi) by high-pressure liquid chromatography.

Cassia bark or cortex cinnamomi, the dried stem bark of Cinnamomum cassia Presl. (Lauraceae), is a popular natural spice and a commonly used herb in traditional Chinese medicine. However, adulterants are frequently found in the market. In this study, 44 samples of Cassia bark including bark from seven related Cinnamomum species were collected from fields and market. Four characteristic components, cinnamaldehyde, cinnamic acid, cinnamyl alcohol, and coumarin were determined by RP-HPLC, and a fingerprint comprised of five markers was established. These results showed that cassia barks contained high contents of cinnamaldehyde (13.01-56.93 mg/g). The highest content of cinnamaldehyde (up to 93.83 mg/g) was found in debarked cortex, which is traditionally regarded as having the best quality in local herb shops. In contrast, the adulterants from the other Cinnamomum species, C. wilsonii Camble, C. japonicum Sieb., C. mairei Levl. and C. burmanii (Nees) Blume, contained low contents of cinnamaldehyde (<2.00 mg/g). The content of cinnamaldehyde in C. loureirii Nees was comparable to that in C. cassia. It is suggested that five characteristic peaks by HPLC are suitable for distinguishing genuine cassia bark from the adulterants and could be applied in the quality control of this commodity.

Acrolein↗
PubMed2005

Recent advances in trichosanthin, a ribosome-inactivating protein with multiple pharmacological properties.

Trichosanthin (TCS), a ribosome-inactivating protein extracted from the root tuber of Chinese medicinal herb Trichosanthes kirilowii Maximowicz, has multiple pharmacological properties including abortifacient, anti-tumor and anti-HIV. It is traditionally used to induce abortion but its antigenicity and short plasma half-life have limited the repeated clinical administration. In this review, work to locating antigenic sites and prolonging plasma half-life are discussed. Studies on structure-function relationship and mechanism of cell entry are also covered. Recently, TCS has been found to induce apoptosis, enhance the action of chemokines and inhibit HIV-1 integrase. These findings give new insights on the pharmacological properties of TCS and other members of ribosome-inactivating proteins.

Anti-HIV Agents↗
PubMed2004

Application of cytochrome b DNA sequences for the authentication of endangered snake species.

In order to enforce the conservation program and curbing the illegal trading and consumption of endangered snake species, the value of cytochrome b sequence in the authentication of snake species was evaluated. As an illustration, DNA was extracted, selected cytochrome b DNA sequences amplified and sequenced from six snakes commonly consumed in Hong Kong. Cataloging with sequences available in public, a cytochrome b database containing 90 species of snakes was constructed. In this database, sequence homology between snakes ranged from 70.68 to 95.11%. On the other hand, intraspecific variation of three tested snakes was 0-0.98%. Using the database, we were able to determine the identity of six meat samples confiscated by the Agriculture, Fisheries and Conservation Department, HKSAR.

Animals↗
PubMed2004

Characterization of medicinal Epimedium species by 5S rRNA gene spacer sequencing.

Sequences of 5S rRNA gene spacer were used to identify Epimedium brevicornu Maxim., E. sagittatum (Sieb. et Zucc.) Maxim., E. wushanense T. S. Ying, E. pubescens Maxim., and E. koreanum Nakai. These species are listed as source plants of Chinese medicine 'Ying Yang Huo' in the Chinese Pharmacopoeia. The neighbor-joining method was used in a sequence analysis of Epimedium species. A position-specific nucleotide was found in the 5S rRNA gene spacer for E. pubescens, E. wushanense, and E. brevicornu. A 19-bp deletion was found for E. koreanum in the 5S rRNA gene spacer. E. koreanum was most divergent from the other four endemic Chinese species of Epimedium.

DNA, Plant↗
PubMed2003

Glycogen synthase kinase-3 beta-mediated tau phosphorylation in cultured cell lines.

To study further the role of glycogen synthase kinase-3beta on tau phosphorylation, glycogen synthase kinase-3beta and tau expression vectors were co-transfected into CHO-K1, COS-7 and SH-SY5Y cell. Tau phosphorylation was assessed by phosphorylation-dependent antibodies AT-8, AT-180, AT-270 and PHF-1. The AT-270 and AT-8 epitopes were consistently phosphorylated by glycogen synthase kinase-3beta in the three cell lines. Phosphorylation on AT-180 epitope was significant in CHO-K1 and SH-SY5Y cells while PHF-1 epitope was hyper-phosphorylated only in SH-SY5Y cells. We also found that lithium induces phosphorylation of the serine 9 residue of glycogen synthase kinase-3beta together with inhibition of tau phosphorylation on PHF-1 epitope in all the three cell lines. This suggests a novel mechanism whereby lithium-mediated inhibition of GSK-3beta activity influences tau phosphorylation.

Animals↗
PubMed2003

Structural basis for the interaction of [E160A-E189A]-trichosanthin with adenine.

Trichosanthin is a ribosome-inactivating protein that cleaves specifically the N-glycosidic bond of A-4324 of 28S rRNA. Trichosanthin and its variant [E160A-E189A]-trichosanthin were found to bind an adenine base with a K(d) value of approximately 0.2mM. To determine how this doubly mutated variant of trichosanthin interacts with adenine, the co-crystal structure of [E160A-E189A]-trichosanthin and adenine was resolved to 0.193nm which revealed that the active site conformation of the doubly mutated variant is isomorphous to wild-type trichosanthin. Water molecules were found at locations corresponding to the eliminated side chain of Glu-160 and Glu-189. On the other hand, the adenine base interacted with [E160A-E189A]-trichosanthin in a manner similar to that in wild-type trichosanthin. Our structural analysis illustrates that Glu-160 and Glu-189 in trichosanthin do not play an important role in maintaining the active site conformation and binding adenine, an essential step for substrate-enzyme interaction. On the other hand, removal of two glutamate residues changed a large patch of negatively charged surface to a positive charge, which may account for the destabilization of the oxocarbenium-like transition-state and the significant decrease in ribosome-inactivating activity in [E160A-E189A]-trichosanthin.

Adenine↗
PubMed2003

DNA microarray for identification of the herb of dendrobium species from Chinese medicinal formulations.

A DNA microarray for detecting processed medicinal Dendrobium species (Herba Dendrobii) was constructed by incorporating the ITS1-5.8S-ITS2 sequences of 16 Dendrobium species on a glass slide. Using fluorescence-labeled ITS2 sequences as probes, distinctive signals were obtained for the five medicinal Dendrobium species listed in the Chinese Pharmacopoeia. The established microarray was able to detect the presence of D. nobile in a Chinese medicinal formulation containing nine herbal components.

DNA, Plant↗