Background: Sialic acids are a family of ninecarbon sugar compounds with carboxylic acyl derivatives. It exists in bacteria, fish, mammals and other living organisms, participates in and regulates many important life ...Background: Sialic acids are a family of ninecarbon sugar compounds with carboxylic acyl derivatives. It exists in bacteria, fish, mammals and other living organisms, participates in and regulates many important life events, such as cell recognition, membrane flow, endocytosis and so on. Sialic acid is usually located in the outermost layer of the sugar part of the cell membrane and the key positions of secreted glycoconjugates (glycolipids, glycoprotein and lipopolysaccharide). Sialic acid (Sia) is an important material foundation for variety of the structure and founction of glycoconjugates. Sia has been known as nearly 50 members, including N-acetylneuraminic acid (Neu5Ac), N-glycoulylneuraminic acid (Neu5Gc) and deaminoneuraminic acid (KDN) as its core monomer. The rest of the sialic acids are derived from these three monomers. The contents of Sia in Chinese food products are unknown. Objective: To determine the contents of Sia in raw and cooked red meat, seafood, poultry and so on. Design: The following food products were purchased from a Chinese supermarket: pork, beef, lamb, salmon, cod, tuna, cow milk, cheese, butter, duck, chicken and chicken eggs. Human milk was collected from Xiamen Maternity and Child Health Care Hospital (Xiamen, China). All tissues were homogenized and hydrolyzed with 0.05 M, 0.1 M and 0.2 M TFA for 150 min at 80°C in dark, respectively. The concentrations of Neu5Ac, Neu5Gc and KDN were determined by using HPLC with fluorescence detector. Results: The contents of total Sia (μg/g tissue or μg/mL liquid sample) in Chinese raw meat were highest in lamb (269.60), followed by pork (254.88), duck (200.63), chicken (162.86) and beef (88.03). The percentages of Neu5Gc were 36.08%, 26.48%, 0%, 0% and 28.40%, respectively. Cod contained higher levels of Sia (171.63) than salmon (104.43) and tuna (77.98). Only Neu5Ac was 50 found in detected aquatic product. Egg yolk contained the highest level of Sia (682.04), and a higher level of Sia (390.67) was found in the egg white. Also our result showed that human milk contained extremely high level of Sia (602.55). Neu5Ac was the predominant form of Sia in all the deteced samples. KDN was found in cow milk only among the samples, the content was 1.14 μg/g. Conclusion: The highest content of Sia in examined Chinese foods was found in 56 eggs, followed by lamb, pork, duck, cod, chicken, salmon, beef and tuna. Knowledge of the Sia content in conventional foods may help us to better understand possible medical disorders involving the uptake of the “non-human” Neu5Gc from our diet.展开更多
[Objectives] This study was conducted to determine capsaicin and dihydrocapsaicin in capsicum products. [Methods]The sample was ultrasonically extracted with anhydrous ethanol as the extraction solvent for capsaicin a...[Objectives] This study was conducted to determine capsaicin and dihydrocapsaicin in capsicum products. [Methods]The sample was ultrasonically extracted with anhydrous ethanol as the extraction solvent for capsaicin and dihydrocapsaicin,followed by centrifugation. The extract was subjected to HPLC separation with methanol-water( 65∶ 35) as the mobile phase,and a fluorescence detector( Ex = 229 nm,Em = 320 nm) was used to detect capsaicinoids in the sample. [Results] Capsaicin and dihydrocapsaicin had a good linear relationship in the range of 1-200 mg/L( R_1~2= 0. 999 8,R22= 0. 999 6). The detection limits were both 0. 007 mg/kg; the quantification limits were both 0. 02 mg/kg; the precision was 0. 235% and 0. 754%,respectively; and the average recoveries were95. 94% and 95. 39%,respectively. [Conclusions]The method is simple,rapid,with good sensitivity and precision,and is suitable for detecting capsaicin substances in capsicum products.展开更多
A new SPME/HPLC interface is developed. It is based on thermal desorption from the SPME fiber and organic solvent collection of the desorbed analytes by sweeping them with an argon flow into a small organic solvent vo...A new SPME/HPLC interface is developed. It is based on thermal desorption from the SPME fiber and organic solvent collection of the desorbed analytes by sweeping them with an argon flow into a small organic solvent volume which is further injected into the HPLC chromatograph. Extraction and desorption parameters were investigated using five PAHs of different volatilities (naphthalene, acenaphthalene, fluorene, phenanthrene and anthracene) as test compounds and fluorimetric detection. Regression coefficients closed to 0.99 with RDS = 3) and detection limits in the range 0.07 - 0.99 μg.L-1 were found. A method was applied to determine the above PAHs in water samples. The results were compared with those supplied by the 550.1 EPA method showing the agreement of both methods at the 0.05 significance level.展开更多
文摘Background: Sialic acids are a family of ninecarbon sugar compounds with carboxylic acyl derivatives. It exists in bacteria, fish, mammals and other living organisms, participates in and regulates many important life events, such as cell recognition, membrane flow, endocytosis and so on. Sialic acid is usually located in the outermost layer of the sugar part of the cell membrane and the key positions of secreted glycoconjugates (glycolipids, glycoprotein and lipopolysaccharide). Sialic acid (Sia) is an important material foundation for variety of the structure and founction of glycoconjugates. Sia has been known as nearly 50 members, including N-acetylneuraminic acid (Neu5Ac), N-glycoulylneuraminic acid (Neu5Gc) and deaminoneuraminic acid (KDN) as its core monomer. The rest of the sialic acids are derived from these three monomers. The contents of Sia in Chinese food products are unknown. Objective: To determine the contents of Sia in raw and cooked red meat, seafood, poultry and so on. Design: The following food products were purchased from a Chinese supermarket: pork, beef, lamb, salmon, cod, tuna, cow milk, cheese, butter, duck, chicken and chicken eggs. Human milk was collected from Xiamen Maternity and Child Health Care Hospital (Xiamen, China). All tissues were homogenized and hydrolyzed with 0.05 M, 0.1 M and 0.2 M TFA for 150 min at 80°C in dark, respectively. The concentrations of Neu5Ac, Neu5Gc and KDN were determined by using HPLC with fluorescence detector. Results: The contents of total Sia (μg/g tissue or μg/mL liquid sample) in Chinese raw meat were highest in lamb (269.60), followed by pork (254.88), duck (200.63), chicken (162.86) and beef (88.03). The percentages of Neu5Gc were 36.08%, 26.48%, 0%, 0% and 28.40%, respectively. Cod contained higher levels of Sia (171.63) than salmon (104.43) and tuna (77.98). Only Neu5Ac was 50 found in detected aquatic product. Egg yolk contained the highest level of Sia (682.04), and a higher level of Sia (390.67) was found in the egg white. Also our result showed that human milk contained extremely high level of Sia (602.55). Neu5Ac was the predominant form of Sia in all the deteced samples. KDN was found in cow milk only among the samples, the content was 1.14 μg/g. Conclusion: The highest content of Sia in examined Chinese foods was found in 56 eggs, followed by lamb, pork, duck, cod, chicken, salmon, beef and tuna. Knowledge of the Sia content in conventional foods may help us to better understand possible medical disorders involving the uptake of the “non-human” Neu5Gc from our diet.
文摘[Objectives] This study was conducted to determine capsaicin and dihydrocapsaicin in capsicum products. [Methods]The sample was ultrasonically extracted with anhydrous ethanol as the extraction solvent for capsaicin and dihydrocapsaicin,followed by centrifugation. The extract was subjected to HPLC separation with methanol-water( 65∶ 35) as the mobile phase,and a fluorescence detector( Ex = 229 nm,Em = 320 nm) was used to detect capsaicinoids in the sample. [Results] Capsaicin and dihydrocapsaicin had a good linear relationship in the range of 1-200 mg/L( R_1~2= 0. 999 8,R22= 0. 999 6). The detection limits were both 0. 007 mg/kg; the quantification limits were both 0. 02 mg/kg; the precision was 0. 235% and 0. 754%,respectively; and the average recoveries were95. 94% and 95. 39%,respectively. [Conclusions]The method is simple,rapid,with good sensitivity and precision,and is suitable for detecting capsaicin substances in capsicum products.
文摘A new SPME/HPLC interface is developed. It is based on thermal desorption from the SPME fiber and organic solvent collection of the desorbed analytes by sweeping them with an argon flow into a small organic solvent volume which is further injected into the HPLC chromatograph. Extraction and desorption parameters were investigated using five PAHs of different volatilities (naphthalene, acenaphthalene, fluorene, phenanthrene and anthracene) as test compounds and fluorimetric detection. Regression coefficients closed to 0.99 with RDS = 3) and detection limits in the range 0.07 - 0.99 μg.L-1 were found. A method was applied to determine the above PAHs in water samples. The results were compared with those supplied by the 550.1 EPA method showing the agreement of both methods at the 0.05 significance level.
