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1.
Combined measurements of piezoelectric quartz crystal impedance (PQCI) and electrochemical impedance (EI) were utilized in situ to monitor the adsorption of bovine serum albumin (BSA) onto the newly prepared Au colloid-modified electrode and study the binding process of tannic acid (TA) to BSA on the BSA-modified electrode surface. The time courses of the resonant frequency and the equivalent parameters of the sensor were simultaneously obtained during BSA adsorption and TA-BSA binding. Compared with the bare gold electrode, the Au colloid-modified gold electrode showed better biocompatibility, and the absorption capacity for BSA was increased by approximately 2.4 times. The observed frequency decrease was ascribed to the mass increase of the sensor surface resulting from the TA-BSA binding, which is believed to result mainly from the hydrogen bonding from FT-IR characterization. The maximal molar binding ratio of TA binding to immobilized BSA obtained from the frequency shift of the adsorbed BSA and TA was estimated to be 10.3:1. On the basis of the frequency decrease with time, the kinetics of the binding was quantitatively studied. By way of fitting the experimental data, the kinetics parameters, that is, binding and dissociation constant (k1, k(-1)), and the binding equilibrium constant (ka) were determined, giving values of 9.51 x 10(4) M(-1) s(-1), 3.15 s(-1), and 3.1 x 10(4) M(-1), respectively.  相似文献   

2.
A liquid chromatographic (LC) method for determining tenuazonic acid (TA) and alternariol methyl ether (AME) in tomatoes and tomato products is described. The Alternaria metabolites are extracted from a water slurry of the sample with CHCl3, the mixture is centrifuged, and the extract is fractionated on a silica gel column. Reverse phase LC with an ultraviolet detector (for TA) and a fluorescence detector (for AME) connected in series is used for final separation and determination. The limit of determination for TA and AME is 25 and 3 ng/g, respectively, with average recoveries from catsup of 83 and 68%, respectively. The LC method also detects alternariol, but interfering peaks in some samples prevent accurate quantitation. Chemical ionization mass spectrometry (CIMS) is used to confirm TA. Samples (142) of tomatoes collected from commercial processing lines were analyzed; TA was found in 73 samples (0.4-70 micrograms/g).  相似文献   

3.
Astringency, an orosensory sensation associated with dietary tannins, contributes to food appetitiveness/aversiveness. However, astringency perception varies greatly among individuals. This study examined whether genetically homogeneous na?ve mice display appetitiveness/aversiveness when provided with tannin-containing drink solutions. Ingestion of serial dilutions of tannic acid (TA) by inbred mice (A/Snell) was assessed by a one-bottle preference test. Drink intake was far predominant at night (circadian rhythm). TA concentration-dependently inhibited daily drink consumption. Overnight consumption of TA solutions (range = 0.5-8 g/L) decreased linearly to zero during the first night and was recovered significantly during subsequent nights. TA also inhibited drink consumption in another two inbred mouse strains. The protein fraction of saliva collected from naive mice was markedly reactive with TA at the concentrations shown to affect drink consumption. Thus, testing for drink ingestion in inbred mice during short-term (overnight) exposure to tannin-containing liquid foods represents an advantageous animal model for assessing astringency.  相似文献   

4.
A method was developed for the quantitative determination of the neurotoxic nonprotein amino acid, 3-N-oxalyl-L-2,3-diaminopropionic acid (beta-ODAP), and its nontoxic alpha-isomer, 2-N-oxalyl-L-2, 3-diaminopropionic acid (alpha-ODAP), in the plant samples of Lathyrus sativus after derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) by reversed-phase high-performance liquid chromatography (HPLC). Hippuric acid was used as an internal standard. A linear response was recorded in the concentration rang 0.32-32 nmol with r > 0.999. The RP HPLC detection limit for both isomers is 1.8 ng. According to different experimental needs, a ternary gradient system can be used to determine toxin and other nonprotein amino acids. The RP HPLC method and a colorimetric method were compared for measuring ODAP.  相似文献   

5.
壳聚糖没食子酸衍生物酶法制备及对鲜切苹果的保鲜效果   总被引：4，自引：3，他引：1  
为提高壳聚糖水溶性和保鲜性能,该文以没食子酸为配体,漆酶为催化剂催化壳聚糖与没食子酸发生接枝反应,得到壳聚糖没食子酸衍生物,对其结构进行了初步表征,并初步探讨了其对鲜切苹果的保鲜效果。结果表明,衍生物接枝率为72.80%,溶解度达到92.77%,没食子酸中的羧基与壳聚糖分子的氨基发生了迈克尔加成反应,在壳聚糖的C2位生成了酰胺键。14℃下贮藏4 d后,10 mg/m L衍生物处理的苹果硬度损失率仅为10.23%,比空白组、壳聚糖处理组和壳聚糖没食子酸物理复合物处理组分别低20.90%(P0.05)、16.60%(P0.05)和15.60%(P0.05);可溶性固形物、维生素C、谷胱甘肽和多酚质量分数分别为12.93%,1.23 mg/(100 g),6.26 mg/(100 g)和6.24 mg/(100 g),分别比空白组高16.47%(P0.05),48.78%(P0.05),24.92%(P0.05)和43.75%(P0.05);多酚氧化酶和过氧化物酶活性分别比空白组低36.73%(P0.05)和76.94%(P0.05);菌落总数为16.00×10~4 CFU/g,显著低于空白组、壳聚糖处理组和壳聚糖没食子酸物理复合物处理组(P0.05)。结果表明,漆酶可催化壳聚糖与没食子酸发生接枝反应,得到的壳聚糖没食子酸衍生物对鲜切苹果具有较好的保鲜效果。  相似文献   

6.
没食子酸烷基酯是一类优良的抗氧化剂，具有潜在的药用价值。为了避免化学合成方法带来的弊端，建立了生物合成没食子酸烷基酯的方法。利用单宁酶在有机相可成功地催化没食子酸烷基酯的合成。在合成没食子酸丙酯(PG)、没食子酸丁酯(BG)和没食子酸戊酯(AG)的反胶束(reverse micelle, RM)催化合成体系中，反胶束组成为双(2-乙基己基)磺基琥珀酰钠(AOT)、异辛烷和水。单宁酶浓度为0.6 mg/mL；pH值为6； W0(水与表面活性剂的摩尔比)分别为15、15和12.5；反应温度分别为30、40和45℃；AOT浓度分别为0.1、0.2和0.2 mol/L时，没食子酸转化率分别为87.4%、90.3%和92.5%。3个体系中由于底物脂肪醇的不同，致使各种因素对单宁酶催化活力的影响不同。  相似文献   

7.
This paper describes a sensitive isocratic HPLC/ECD method developed for the determination of rosmarinic acid (RA) in plant material, animal feed, and pig plasma. The plasma sample preparation only includes protein precipitation and adjustment of the pH. The applicability of the method was tested on plasma samples of pigs that were exposed to a 91-day oral intake of RA via feed enriched by aerial parts of Prunella vulgaris. The plasma was directly analyzed using the method described as well as after enzymatic hydrolysis. When no hydrolysis step was included, RA and caffeic acid (CA) were quantified in the plasma. In hydrolyzed plasma samples, several other metabolites were determined, including dihydrocaffeic, ferulic, and dihydroferulic acid. The dual-channel coulometric detection employed, as an alternative to mass spectrometry, offers good selectivity and sensitivity owing to the electrochemical properties of the phenolic constituents.  相似文献   

8.
A high-performance liquid chromatography (HPLC) method was developed for measuring the concentrations of clovamide-type phenylpropenoic acid amides (N-caffeoyldopamine and N-caffeoyltyramine) in cell and plasma samples. The separation was performed on a Nova-Pak C18 column using an isocratic buffer with a coulometric electrochemical detector with four electrode channels. Using the HPLC method, N-caffeoyldopamine and N-caffeoyltyramine could be detected with good peak resolutions at respective retention times (4 and 6.4 min). The calibration curves were linear over the ranges (0.1 and 100 microM), and their lower limit of detection was as little as 100 fmol. For quantifying N-caffeoyldopamine and N-caffeoyltyramine in cell and plasma samples, the samples were extracted by extraction methods with more than 95% recoveries. After extraction, the amides were detected with the same sensitivity, peak resolutions, and retention times. Using this method, plasma concentrations of N-caffeoyltyramine were determined in blood samples collected at 12, 24, 30, 36, 48, 60, and 75 min after the oral administrations of N-caffeoyltyramine (0.5 mg and 2 mg/30 g body weight). This HPLC method with an electrochemical detector is the first reported method able to quantify N-caffeoyldopamine and N-caffeoyltyramine in biological samples with excellent detection limits, peak resolutions, discrete retention times, and consistent reproducibility.  相似文献   

9.
Abstract

Can humic acid (HA) and glutamic acid (GA), when added to tomato (Lycopersicon esculentum Mill. cv. ‘Hongyangli’) nutrient solution in a hydroponic system, improve growth? Tomato seedlings were grown in six nutrient solutions: (1) control (C), (2) C + 25 mg L?1 HA (HA1); (3) C + 50 mg L?1 HA (HA2); (4) C + 100 mg L?1 GA; (5) HA1 + GA; (6) HA2 + GA. Various biochemical and physiological parameters were measured. HA increased photosynthesis rate and mesophyll conductance. HA did not significantly affect transpiration, stomatal conductance, titratable acidity, or antioxidant activity. In addition, GA improved protein and sugar content, mesophyll conductance and yield. The combination of HA and GA was more effective, especially with 50 mg L?1 HA. The activity of superoxide dismutase (SOD) and peroxidases (POD) did not change in the presence of HA or GA. Malondialdehyde (MDA) content increased by 30% in HA2 together with GA. HA has a positive effect on tomato hydroponic growth when applied with GA. This expands the use of HA and GA for horticultural commodities in hydroponic systems.  相似文献   

10.
A rapid, selective, sensitive, accurate, and inexpensive immunosensor for gibberellin acid detection was designed by coupling immunoassay with the square wave anodic stripping voltammetry (SWASV) technique involving copper ion labeled antigen in the competitive immunoreaction. The response signal expressed as the percentage of current reduction CR % (y) is linearly related to the concentration of GA (x) in the 1 microg/mL to approximately 150 microg/mL range with a regression equation of the form y = 0.44x + 15.59 and a correlation coefficient of 0.99. The results of the immunosensor assay were compared with those obtained by HPLC and ELISA, which show a satisfactory agreement. The immunosensor was used to determine the GA content in the hybrid rice grain samples taken in the growing period.  相似文献   

11.
A simple analytical method for the quantitative determination of phenols, flavones, and lignans in virgin olive oils was developed. The polar fraction was isolated from small amounts of oil sample (2.5 g) by solid-phase extraction (SPE) using diol-phase cartridges, and the extract was analyzed by reversed-phase HPLC coupled with diode array UV detection. Chromatographic separation of pinoresinol, cinnamic acid, and 1-acetoxypinoresinol was achieved. Repeatability (RSD < 6.5%), recovery (> 90%), and response factors for each identified component were determined. SPE on amino-phase cartridges was used for isolating acidic phenols and as an aid for phenol identification. For the first time, 2-(4-hydroxyphenyl)ethyl acetate was detected in olive oils. The aldehydic structure of the ligstroside aglycon was confirmed by NMR spectroscopy. The colorimetric determination of total o-diphenolic compounds by reaction with molybdate was consistent with their HPLC determination. Differences between results obtained by liquid-liquid extraction and SPE were not statistically significant.  相似文献   

12.
A stable-isotope liquid chromatography-mass spectrometry (LC-MS) assay was developed for the quantitative determination of folic acid in fortified foods. Folic acid was extracted from food samples into a phosphate buffer, purified on a C-18 Sep-Pak cartridge, and analyzed by LC-MS in the negative ion mode using electrospray ionization. The analyte was quantified using (13)C(5)-folic acid as an internal standard. The coefficient of variation for the precision of the method was 5.6% based on the analysis of four sample replicates. The accuracy of the method was assessed using a standard method of addition of folic acid to a shredded whole-wheat cereal. The quantitative determination of folic acid in this matrix was linear over 1 order of magnitude having a concentration range of 2.4 to 24 microg/g of food (or 0.05 to 0.5 microg of analyte injected into the LC-MS). The overall quantitative efficiency of the method was evaluated using a standard reference material (infant formula SRM 1846). The method was applied to the determination of folic acid in several test samples (fortified breakfast cereals), and the values were in accord with the manufacturer's claim. This method advances a LC-MS technique for the determination of folic acid in fortified foods based on stable-isotope dilution methodology. The specificity of the technique and quantitative accuracy of the method in various food substrates suggests that the method may be adapted for routine analysis in other fortified foods.  相似文献   

13.
Some tannins, plant-derived polyphenolic compounds, can rapidly affix to soil and affect the solubility of labile soil-N but a more complete understanding of the nature and persistence of tannin-soil interactions is needed. Forest and pasture soils from two depths were treated for 1 h with cool (23 °C) water (Control) or solutions that added 10 mg g−1 soil tannic acid (TA), an imprecisely defined mixture of galloyl esters, gallic acid (GA), a phenol, or β-1,2,3,4,6-penta-O-galloyl-d-glucose (PGG), a hydrolyzable tannin. Soluble-C and N, in treatment supernatants, was measured to uncover evidence for sorption of treatments or effects on extraction of soil-N. Significant amounts of soluble-C, added with treatments, were not recovered in supernatants indicating sorption of nearly 90% of the PGG-C, about 75% of the TA-C but less than 25% of the GA-C in surface soil. Disappearance of soluble-C from treatment supernatants was accompanied by a corresponding reduction of total phenolic content. Treatments added a negligible amount of N to soil; but while PGG and TA reduced soluble-N, in extracts from surface soil, GA had little effect. Soluble-N in extracts was composed mainly of organic-N. Effects of tannins persisted in surface soil through 12 washings with hot water (80 °C), suggesting the formation of stable complexes with soil. The proportion of initial soil-C and N remaining after all extractions was higher in samples treated with PGG or TA than either the Control or GA treatment. We conclude PGG readily sorbs to soil and reduces the solubility of soil organic-N unlike GA, its simple monomeric constituent. These differences could be especially important near the surface where quantities of soil organic matter and biological activity are comparatively large and most easily affected by management.  相似文献   

14.
A rapid, selective, and sensitive LC-MS/MS method was developed for the quantitative determination of domoic acid in serum and urine samples. Samples were prepared for analysis using an Oasis HLB SPE column. Determination was by a reversed phase HPLC using a mixture of methanol, acetonitrile, and water containing 1% acetic acid and an electrospray ionization (ESI) ion-trap mass spectrometer (Finnigan LCQ). The method was validated by analyzing five replicates each of negative control bovine serum or urine fortified with domoic acid at the 0.005 microg/g method detection limit (MDL) and at the 0.05 microg/g level. Recoveries ranged from 90 to 95% for fortifications at the MDL and from 92 to 98% for fortifications 10 times higher than the MDL. The diagnostic utility of the method was tested by analyzing samples from live animals showing clinical signs suggestive of domoic acid poisoning submitted to the veterinary toxicology laboratory.  相似文献   

15.
The amino acid analysis method using precolumn phenylisothiocyanate (PITC) derivatization and liquid chromatography was modified for accurate determination of methionine (as methionine sulfone), cysteine/cystine (as cysteic acid), and all other amino acids, except tryptophan, in hydrolyzed samples of foods and feces. A simple liquid chromatographic method (requiring no derivatization) for the determination of tryptophan in alkaline hydrolysates of foods and feces was also developed. Separation of all amino acids by liquid chromatography was completed in 12 min compared with 60-90 min by ion-exchange chromatography. Variation expressed as coefficients of variation (CV) for the determination of most amino acids in the food and feces samples was not more than 4%, which compared favorably with the reproducibility of ion-exchange methods. Data for amino acids and recoveries of amino acid nitrogen obtained by liquid chromatographic methods were also similar to those obtained by conventional ion-exchange procedures.  相似文献   

16.
Micellar electrokinetic chromatography (MEKC) was developed as a method for quantitative determination of gibberellic acid (GA3) in fermentation broth and commercial products, using 25 mM disodium tetraborate as a buffer at pH 9.2 and 100 mM sodium dodecyl sulfate as a micellar phase. The baseline resolution (Rs of GA3 from other compounds in fermentation broth was achieved with Rs > 2.5. The addition of methanol or acetonitrile in the MEKC buffer did not give a better resolution. Advantages of this MEKC method include high accuracy and precision and no sample preparation except for dilution and filtration.  相似文献   

17.
A novel stable precursor of ascorbic acid (vitamin C), 2-O-(beta-D-glucopyranosyl)ascorbic acid, was isolated from both the ripe fresh fruit and dried fruit of Lycium barbarum L., a plant of the Solanaceae family. The chemical structure was inferred by instrumental analyses and confirmed by chemical synthesis. The dried fruit of Lycium barbarum L. contained ca. 0.5% of it, which is comparable to the ascorbic acid content of fresh lemons. It increased the blood ascorbic acid by oral administration to rats, and it was also detected in blood from the portal vein.  相似文献   

18.
Five methods were investigated for the determination of levulinic acid in soy sauce to determine the addition of protein hydrolysate, mainly acid hydrolysate of defatted soybeans. Best results were obtained by using liquid chromatography (LC) with 0.004 M HClO4 as the mobile phase and bromcresol purple as a post-column reagent. An innovative LC method with 0.1% H3PO4 as eluant was developed for determination of levulinic acid at 280 nm in soy sauce. This was the most time-saving method.  相似文献   

19.
Chemically treated dietary supplements (CTDS) were prepared with defatted soy flour, sunflower oil, dl-alpha-tocopheryl acetate (TA), and 2,3-butanedione (a generally recognized as safe chemical), and the effects on alpha-tocopherol (VE) concentration and fatty acid profile in ewe's milk were estimated. Ewes fed control diet (CD) had the lowest levels of milk VE (0.66 microg/mL) and serum VE (1.59 microg/mL). Feeding ewes the CD plus 500 IU of TA increased milk and serum VE by 30 and 70%, respectively, compared to ewes fed the CD. The CTDS-fed ewes showed further increased milk and serum VE levels by 40 and 32%, respectively, over those in ewes fed the CD plus 500 IU of TA. Feeding ewes CTDS did not affect milk fat content (3.13%) but altered the fatty acid composition by decreasing the levels of hypercholesteremic fatty acids, while increasing the content of linoleic acid (8.5%). Inclusion of CTDS in ruminant diets might produce nutritionally enhanced milk products.  相似文献   

20.
A high-performance liquid chromatographic (HPLC) method with diode-array detection (DAD) was used to identify and quantify free and total phenolic acids (m-hydroxybenzoic acid, p-hydroxybenzoic acid, protocatechuic acid, gallic acid, vanillic acid, syringic acid, o-coumaric acid, m-coumaric acid, p-coumaric acid, caffeic acid, ferulic acid, sinapic acid, chlorogenic acid, and ellagic acid) in plant foods. Free phenolic acids were extracted with a mixture of methanol and 10% acetic acid. Bound phenolic acids were liberated using first alkaline and then acid hydrolysis followed by extraction with diethyl ether/ethyl acetate (1:1). All fractions were quantified separately by HPLC. After HPLC quantification, results of alkali and acid hydrolysates were calculated to represent total phenolic acids. Ellagic acid was quantified separately after long (20 h) acid hydrolysis. The methods developed were effective for the determination of phenolic acids in plant foods. DAD response was linear for all phenolic acids within the ranges evaluated, with correlation coefficients exceeding 0.999. Coefficients of variation for 4-8 sample replicates were consistently below 10%. Recovery tests of phenolic acids were performed for every hydrolysis condition using several samples. Recoveries were generally good (mean >90%) with the exceptions of gallic acid and, in some cases, caffeic acid samples.  相似文献   

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