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305 results on '"Leung, Kelvin Sze-Yin"'

72. Determination of paralytic shellfish toxins in dinoflagellate Alexandrium tamarense by using isotachophoresis/capillary electrophoresis

Author

Wu, Youyi, Ho, Alvin Yam Tat, Qian, Peiyuan, Leung, Kelvin Sze Yin, Cai, Zongwei, Lin, Jinming, Wu, Youyi, Ho, Alvin Yam Tat, Qian, Peiyuan, Leung, Kelvin Sze Yin, Cai, Zongwei, and Lin, Jinming

Abstract

Baseline separation of seven paralytic shellfish toxins (PSTs), namely decarbamoylsaxitoxin (dcSTX), saxitoxin (STX), neosaxitoxin (NEO), gonyautoxin-2 (GTX-2), gonyautoxin-3 (GTX-3), gonyautoxin-1 (GTX-1), and gonyautoxin-4 (GTX-4), was achieved by using capillary ITP (CITP)/CE with UV detection. Separation parameters including duration time and voltage in CITP process, separation voltage, and pH and concentration of buffer were optimized. The developed method provided linear responses from 1.3 to 200 mu M for the PSTs. The LOD ranged from 0.1 to 0.3 mu M. PST extracts from two algal strains of Alexandrium tamarense were analyzed and the toxin concentrations in the samples were quantified with an internal standard method by using NEO as the internal standard. The algal extract of A. tamarense HK9301 contained 332 mu M GTX-2 and 224 mu M GTX-3, while the PSTs were not detected in the extract of A. tamarense CI01.

Published
2006

97. Comparative study on the aristolochic acid I content of Herba Asarifor safe use.

Author

Zhao Z, Liang Z, Jiang Z, Leung K, Chan C, Chan H, Sin J, Man T, Law K, Zhao, Zhong-Zhen, Liang, Zhi-Tao, Jiang, Zhi-Hong, Leung, Kelvin Sze-Yin, Chan, Chi-Leung, Chan, Hon-Yee, Sin, Jaime, Man, Tim-On, and Law, Kwok-Wai

Abstract

Herba Asari (Xixin, Manchurian Wildginger, Asarum spp.) is a traditional Chinese medicinal herb commonly used as a crude drug and an ingredient in patent medicines. The herb contains aristolochic acid I (AA-I), which has recently caused several incidents of poisoning in Hong Kong. Therefore, the safe use of Asarum is questionable. The present study was undertaken to assess the levels of AA-I using liquid chromatography-mass spectrometry (LC/MS) indifferent medicinal parts of Herba Asari and some proprietary Chinese medicines (PCM) containing it as an ingredient. The AA-I content in the aerial and root portions were compared, in the form of water and methanolic extracts. The results showed that all the aerial portions of Herba Asari generally contain higher levels of AA-I than the roots (in water extract: 0.0870.06 microg/g of root and 0.3270.021 microg/g of aerial), and the methanolic extracts typically contained more AA-I than the water extracts. Moreover, all the three PCM studies showed negligible amounts of AA-I(containing 0.0370.006 microg/g). Therefore, the root portion of Herba Asari was recommended for prescription as a decoction instead of grinding it into powder for oral administration. [ABSTRACT FROM AUTHOR]

Published
2008
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98. Distinguishing the medicinal herb Oldenlandia diffusa from similar species of the same genus using fluorescence microscopy.

Author

Liang, Zhi-Tao, Jiang, Zhi-Hong, Leung, Kelvin-Sze-Yin, Peng, Yong, and Zhao, Zhong-Zhen

Abstract

The light microscope is routinely used for microscopic identification of Chinese Materia Medica (CMM). However, the fluorescence microscope has not been used for this purpose until now. The CMM, Baihuasheshecao, mostly used as a component of herb tea, is a well known folk-medicine in China. According to the Chinese Pharmacopoeia, its source is the species Oldenlandia diffusa (Willd.) Roxb. Two other species of the same genus, namely O. corymbosa (L.) Lam and O. tenelliflora Bl., had been found in use as Baihuasheshecao. To find a quick and easy method to distinguish O. diffusa from these similar species of the same genus, the fluorescence microscope was used to investigate the fluorescence emission characteristics of the three tissues, which were compared with light microscopy images of the same material. The results showed that some tissues of the three herbs emit autofluorescence. Specially, the wall of endoderm cells of O. diffusa and O. tenelliflora emit autofluorescence, while similar tissue of O. corymbosa does not. Hence, fluorescence microscopy can be helpful in the identification of CMM. Microsc. Res. Tech. 69:277-282, 2006. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Published
2006
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100. Determination of paralytic shellfish toxins in dinoflagellate Alexandrium tamarenseby using isotachophoresis/capillary electrophoresis

Author

Wu, Youyi, Ho, Alvin Yam Tat, Qian, Pei‐Yuan, Leung, Kelvin Sze‐Yin, Cai, Zongwei, and Lin, Jin‐Ming

Abstract

Baseline separation of seven paralytic shellfish toxins (PSTs), namely decarbamoylsaxitoxin (dcSTX), saxitoxin (STX), neosaxitoxin (NEO), gonyautoxin‐2 (GTX‐2), gonyautoxin‐3 (GTX‐3), gonyautoxin‐1 (GTX‐1), and gonyautoxin‐4 (GTX‐4), was achieved by using capillary ITP (CITP)/CE with UV detection. Separation parameters including duration time and voltage in CITP process, separation voltage, and pH and concentration of buffer were optimized. The developed method provided linear responses from 1.3 to 200 μM for the PSTs. The LOD ranged from 0.1 to 0.3 μM. PST extracts from two algal strains ofAlexandrium tamarense were analyzed and the toxin concentrations in the samples were quantified with an internal standard method by using NEO as the internal standard. The algal extract ofA. tamarenseHK9301 contained 332 μM GTX‐2 and 224 μM GTX‐3, while the PSTs were not detected in the extract of A. tamarense CI01.

Published
2006
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