采用面包酵母制备三磷酸肌醇和四磷酸肌醇的研究

检测了不同厂家生产的面包酵母的植酸酶活力,建立了利用面包酵母降解植酸钠来制备三磷酸肌醇(IP3)和四磷酸肌醇(IP4)的方法.对植酸盐水解液进行阴离子交换树脂吸附之前进行预处理有助于提高其分离IP3和IP4的效率.采用这种方法所制备的IP3和IP4均只有一种异构体,即肌醇(1,2,6)三磷酸[D-I(1,2,6)P3]和肌醇(1,2,5,6)四磷酸[D-I(1,2,5,6)P4].     

三磷酸肌醇清除自由基的作用

采用电子自旋共振波谱仪检测了三磷酸肌醇（IP3）清除羟基自由基（·OH）和超氧阴离子自由基（O）的作用。结果表明：利用Fenton反应体系,酵母和植酸酶制备的IP3对基自由基（·OH）的清除率各达75．34％和73．29％,样品浓度分别为6mg／ml和9mg／ml;利用次黄嘌呤-黄嘌呤氧化酶体系,酵母和植酸酶制备的IP3对超氧阴离子自由基（O）的清除率达72．76％和53．84％,样品浓度分别为18mg／ml和9mg／ml。同时认为IP3之所以对多种疾病具有预防、减轻和治疗效果,主要是因为IP3具有比较强大的清除自由基的功能。     

乳酸菌源共轭亚麻酸的分离制备

乳酸菌发酵产生的共轭亚麻酸(CLNA)在慢性疾病中有重要的生理功能,CLNA由多种异构体组成,各种异构体的生理功能存在差异。建立了分离制备乳酸菌发酵液中游离态CLNA异构体的方法,成功获得了结构单一的CLNA异构体。结果表明:在现有条件下乳酸菌源CLNA单一异构体无法通过薄层色谱法分离;高效液相色谱法可实现乳酸菌源CLNA单一异构体的分离,最优分离制备条件为高效液相色谱柱Ultimate(5XB-C30,4. 6 mm×250 mm)、流动相甲醇-水-甲酸(体积比70∶30∶0. 01)、流速1 m L/min、检测紫外波长205 nm和233 nm。在最优分离制备条件下,保留时间和峰面积的相对标准偏差分别为0. 05%～0. 38%、1. 88%～4. 65%,制备得到的CLNA1纯度为97. 48%,CLNA2的纯度为100%,CLNA3的纯度为65. 30%。该方法重复性好,分离度高,适合分离乳酸菌发酵液中游离形式CLNA。     

新型食品营养强化剂-共轭亚油酸

共轭亚油酸 (Conjgatedlinoleicacid ,CLA)是一类含有共轭双键的亚油酸的异构体 ,由于具有特殊的脂肪链结构使得其具有多种生理功能。c9t11和t10cl2异构体是共轭亚油酸的主要活性异构体。本文对共轭亚油酸的生理功能、代谢、安全性等进行综述。     

不同温度喷雾干燥香菇多糖粉末特性研究

香菇多糖是一种功能性食物成分，具有包括抗肿瘤和抗氧化作用在内的多种生物活性。喷雾干燥技术具有制备粉末的独特优势，研究不同温度喷雾干燥香菇多糖粉末特性可以证明喷雾干燥技术大量制备香菇多糖的可行性。将喷雾干燥风机风量设定为90 m3/h，进料量200 mL/h，喷雾干燥温度从200℃起并逐步降低，经喷雾干燥获得不同喷雾干燥温度香菇多糖粉并测定其特性。结果显示，喷雾干燥温度可低至30℃，所得粉末干燥、蓬松、细腻、溶解性好，粉末含水量低于6%，容积密度小。香菇多糖粉末多糖含量25%～28.5%，具有较大吸湿性。研究表明，喷雾干燥适合制备香菇多糖粉末，且可以在较低温度下进行，此方法不仅能确保香菇多糖的结构和活性稳定，而且能够极大地减小能耗。     

反相高效液相色谱法手性分析和制备全反式虾青素3种异构体

目的建立反相高效液相色谱法(reversed-phase high performance liquid chromatography, RP-HPLC)检测全反式虾青素三种异构体(3R,3′R、3R,3′S和3S,3′S)的分析方法。方法采用了固定相填料为纤维素-三(3,5-二甲基苯基氨基甲酸酯)的手性色谱柱(Ultimate Cellu-DR column),综合考察了流动相和柱温对全反式虾青素3种异构体的分离效果,并采用半制备液相色谱法获得全反式虾青素的3种异构体。结果得到最佳的分析色谱条件:流速为0.80 mL/min,柱温30℃,流动相为甲醇,等度洗脱,检测波长为480 nm。在此条件下,全反式虾青素的3种异构体达到良好分离,分离度均大于2。优化后的半制备色谱条件为:制备柱Ultimate Cellu-DR,流动相为纯甲醇,流速为15.00 mL/min。获得的3种异构体纯度均大于97%。结论该分析方法能有效地区分全反式虾青素的3种异构体,可用于不同来源虾青素的鉴定。     

类胡萝卜素异构化及其对生物活性和生物利用度影响的研究进展

类胡萝卜素是自然界中最常见的脂溶性植物色素，具有抗氧化及预防多种疾病的功能。一般而言，天然类胡萝卜素大多以全反式构型存在，生物活性和生物利用度较低。类胡萝卜素异构化成为顺式异构体是提高其应用价值的重要手段。本文在阐述异构化反应机理的基础上，综述了类胡萝卜素的异构化方法（热致异构化、热促异构化、光致异构化等）、影响异构化反应的因素，以及在不同评估方式下异构化对其生物活性和生物利用度的影响，最后对类胡萝卜素异构化过程中存在的问题及未来研究方向进行展望。     

共轭亚油酸的生理功能及其合成、纯化研究检测方法

共轭亚油酸是一系列位置和几何异构体的总称，其中的活性异构体具有多种重要的生理功能，近年来受到越来越多的重视。对活性共轭亚油酸异构体的主要生理功能、微生物合成共轭亚油酸的微生物菌种及合成途径中的关键性酶、目前使用的共轭亚油酸的化学合成方法、以及共轭亚油酸的纯化及分析检测方法进行了综述。     

人参皂苷Rg分子轨道微扰理论的研究

人参皂苷Rg是具有生理活性的物质，它包括三个异构体：Rg1；Rg2；Rg3其中R83具有很强的抗癌作用。本文通过休克尔分子图形理论对Rg异构体的各分子轨道进行约化，并且根据分子轨道微扰理论求出它们不同本征多项式和本征值。     

基于亲水相互作用色谱-串联离子阱质谱法分析的低聚半乳糖异构体糖苷键的初步鉴定

目的采用亲水相互作用色谱-串联离子阱质谱法分析鉴定低聚半乳糖及其氨基柱分离制备的级分中二糖和三糖异构体组成及其糖苷键特征。方法将二糖和三糖的各个异构体色谱峰的MS~2与MS~3的中性丢失离子特征及相对丰度与文献中相关数据比较,从而推测其异构体结构特征。结果初步定性了量子高科GOS产品中二糖及三糖异构体组成及糖苷键特征;并根据由Sugarpak1色谱柱分离和示差折光检测器检测得到的不同聚合度寡糖的相对百分比及各异构体峰高相对比例计得GOS产品中二糖和三糖的不同糖苷键异构体的相对含量。结论该方法简便、快速,可用于鉴别和表征不同来源的低聚半乳糖产品,有望进一步研究以解決目前乳品饮料等复杂的食品基质中GOS定性定量分析的难题。     

Isolating isomers of perfluorocarboxylates in polar bears (Ursus maritimus) from two geographical locations

The source of involatile, anthropogenic perfluorocarboxylate anions (PFCAs) in biota from remote regions is of heightened interest due to the persistence, toxicity, and bioaccumulation of these materials. Large-scale production of fluorinated compounds is carried out primarily by one of two methods: electrochemical fluorination (ECF) and telomerization. Products of the two processes may be distinguished based on constitutional isomer pattern as ECF products are characteristically comprised of a variety of constitutional isomers. The objective of this research was to develop a method for identifying the constitutional isomer profile of PFCAs in environmental samples and to apply the method to polar bear livers from two different locations. Resolution of constitutional isomers of derivatized PFCAs (8-13 carbons) was accomplished via GC-MS. Seven isomers of an authentic ECF perfluorooctanoate (PFOA) standard were separated. The linear isomer comprised 78% of this standard. Isomer profiles of PFCAs in liver samples of 15 polar bears (Ursus maritimus) from the Canadian Arctic and eastern Greenland were determined by GC-MS. The PFOA isomer pattern in Greenland polar bear samples showed a variety of branched isomers while only the linear PFOA isomer was determined in Canadian samples. Samples of both locations had primarily (>99%) linear isomers of perfluorononanoate and perfluorotridecanoate. Branched isomers of perfluorodecanoate, perfluoroundecanoate, and perfluorododecanoate were determined in the polar bear samples. Unlike the PFOA isomer signature, only a single branched isomer peak on the chromatograms was observed for these longer chain PFCAs. The presence of branched isomers suggests some contribution from ECF sources. However, in comparison to the amount of branched isomers in the ECF PFOA standard, such minor percentages of branched PFCAs may suggest additional input from an exclusively linear isomer source.     

Conjugated linoleic acid isomer concentrations in milk from high‐ and low‐input management dairy systems

BACKGROUND: Different conjugated linoleic acid (CLA) isomers are known to have contrasting physiology or health effects and there is growing evidence that the profile of natural isomers in milk is influenced by the production system. This survey is the first to compare feeding regimes and concentrations of 14 CLA isomers in milk from three production systems in the UK. RESULTS: Total CLA and seven isomers (including C18:2 c9t11 which comprised > 80% of total) were significantly higher in milk from both organically certified and non‐certified low input (LI) systems compared with milk from conventional high input farms. Sampling date also affected concentrations of total CLA and nine isomers; being lowest in March and highest in August. Seasonal differences were greater in milk from LI herds, thought to be due to changes in herbage and/or stage of lactation. Multivariate analysis showed a strong positive relationship between several CLA isomers and increasing levels of fresh forage in the diet. CONCLUSIONS: These results add to the evidence on how management adjustment may improve the profile of CLA isomers in milk fat, although animal or human intervention studies are required to identify the effects of consuming milk with different CLA levels and isomer profiles on human health. Copyright © 2009 Society of Chemical Industry     

c9t11- 和t10c12- 共轭亚油酸抗癌和影响脂质代谢的异同

共轭亚油酸(CLA)是一组位置和构象异构体的总称,异构体c9t11-CLA 和t10c12-CLA 或二者的协同作用赋予了CLA 的许多生理功能,比如抗癌、降低体脂含量、预防糖尿病的发生、降低血脂抑制动脉粥样硬化等;异构体c9t11-CLA 和t10c12-CLA 在结构及来源上存在一定差别--由于双键位置的不同,t10c12-CLA 异构体比c9t11-CLA 异构体更容易氧化;而在生理功能上二者也有差异-- c9t11-CLA 异构体的主要作用是抗癌,而 t10c12-CLA 则是降低体脂、血脂等,大量单一异构体的体外实验研究表明二者在抗癌及脂肪代谢的调节上作用机制也不尽相同。     

Determination of astaxanthin stereoisomers and colour attributes in flesh of rainbow trout (Oncorhynchus mykiss) as a tool to distinguish the dietary pigmentation source

The presence of carotenoids in animal tissue reflects their sources along the food chain. Astaxanthin, the main carotenoid used for salmonid pigmentation, is usually included in the feed as a synthetic product. However, other dietary sources of astaxanthin such as shrimp or krill wastes, algae meal or yeasts are also available on the market. Astaxanthin possesses two identical asymmetric atoms at C-3 and C-3' making possible three optical isomers with all-trans configuration of the chain: 3S,3'S, 3R,3'S, and 3R,3'R. The distribution of the isomers in natural astaxanthin differs from that of the synthetic product. This latter is a racemic mixture, with a typical ratio of 1:2:1 (3S,3'S:3R,3'S:3R,3'R), while astaxanthin from natural sources has a variable distribution of the isomers deriving from the different biological organism that synthesized it. The high-performance liquid chromatographic (HPLC) analysis of all-trans isomers of astaxanthin was performed in different pigment sources, such as red yeast Phaffia rhodozyma, alga meal Haematococcus pluvialis, krill meal and oil, and shrimp meal. With the aim to investigate astaxanthin isomer ratios in flesh of fish fed different carotenoid sources, three groups of rainbow trout were fed for 60 days diets containing astaxanthin from synthetic source, H. pluvialis algae meal and P. rhodozyma red yeast. Moreover, the distribution of optical isomers of astaxanthin in trout purchased on the Italian market was investigated. A characteristic distribution of astaxanthin stereoisomers was detected for each pigment sources and such distribution was reproduced in the flesh of trout fed with that source. Colour values measured in different sites of fillet of rainbow trout fed with different pigment sources showed no significant differences. Similarly, different sources of pigment (natural or synthetic) produced colour values of fresh fillet with no relevant or significant differences. The coefficient of distance computed amongst the feed ingredient and the trout fillet astaxanthin stereoisomers was a useful tool to identify the origin of the pigment used on farm.     

Conjugated fatty acids in food and their health benefits

Conjugated fatty acids (CFAs) are a mixture of positional and geometric isomers of polyunsaturated fatty acids with conjugated double bonds. Reports indicate that CFAs have potent beneficial effects, including antitumor, antiobese, antiatherogenic and antidiabetic activities. The molecules have also been shown to prevent the onset of hypertension. Recent reports suggest that each CFA isomer has different functions, for example the 10trans,12cis isomer of conjugated linoleic acid (CLA) has anticarcinogenic, antiobese and antidiabetic effects, whereas the 9cis,11trans-CLA isomer exerts an anticancer effect. Although it would be interesting to know the effects of CFAs on humans, there are only few reports concerning the anticancer and antiobese effects of CLA in humans. More detailed evaluations of the physiological bioactivities of CFA isomers on lifestyle-related diseases in humans and animals will be of great interest in future studies.     

Isomer distribution of perfluorocarboxylates in human blood: potential correlation to source

Detection of perfluorocarboxylate anions (PFCAs), such as perfluorooctanoate (C7F15COO-, PFOA), at ng/g levels in human tissues has engendered public scrutiny of industrial fluorochemicals. Routes of PFCA exposure for the general human population are likely diverse given direct (industrially produced) and indirect (production from precursor organofluorines) sources. Major industrial production of organofluorines, including PFCAs, stems from either electrochemical fluorination (ECF) or telomerization. ECF products are a mixture of structural isomers (linear and branched perfluoroalkyls) and telomerization products are assumed to have one perfluorocarbon arrangement, typically linear. The objective of this research was to investigate structural isomer patterns of PFCAs in human blood. Volatile derivatives of PFCAs in human blood were analyzed by GC-(NCI)-MS for quantitation and isomers. PFOA was the dominant PFCA (mean 4.4 ng/g). Blood serum isomer profiles consisted of predominantly (mean approximately 98%) the linear isomer for each PFCA (C8-C11). There were similarities in branched isomer patterns of an ECF PFOA standard with both PFOA and PFNA in blood. Direct exposure to ECF PFOA, which has a legacy of production for uses in fluoropolymer industries, is postulated to be a source of the observed branched isomer pattern. Predominance of linear PFCA isomers and the [even PFCA] > [odd PFCA] concentration trend in blood is suggestive of additional input from a strictly linear perfluoroalkyl source.     

Some aspects of the use of high-performance liquid chromatography for the determination of vitamin A in animal feeding stuffs

The application of high-performance liquid chromatography to the determination of vitamin A in animal feeding stuffs has been investigated. Particular emphasis has been given to some of those aspects that would be of importance to official control methods. Vitamin A exists as six geometric isomers, some or all of which may be present in feed extracts. The effect of this on both ultraviolet and fluorescence quantitation is described, using all-trans retinol and 13-cis retinol as examples of the different isomers. The isomers were eluted coincidentally from a reversed-phase column; information on the isomeric composition of the feed extracts was obtained by means of the maleic anhydride reaction. These results were confirmed by a normal phase chromatographic procedure which resolved all-trans and 13-cis retinol.