手性色谱法测定L-硒-甲基硒代半胱氨酸含量的研究

L-硒-甲基硒代半胱氨酸是一种新型硒源类的食品营养强化剂,而D-硒-甲基硒代半胱氨酸的安全性尚没有相关研究,目前对于L-硒-甲基硒代半胱氨酸含量的测定方法多集中在测定硒-甲基硒代半胱氨酸含量,无法检测到其中L-硒-甲基硒代半胱氨酸的含量。本文建立了通过手性色谱柱分离、标准曲线法测定L-硒-甲基硒代半胱氨酸的高效液相色谱法(HPLC)。实验使用EC250/4NUCLEOSIL Chiral-1手性色谱柱(4 mm×250 mm,5μm),流动相为0.4mmol/L Cu SO4·5H2O水溶液,柱温为35℃,流速为1.0 m L/min,进样量为20μL,检测波长为240 nm;在该条件下L-硒-甲基硒代半胱氨酸的检测线性范围为0.541~1.352 mg/ml,线性相关系数R达0.9999,在线性范围内精密度和稳定性良好,平均回收率为97.73%。该方法操作简单,结果准确,可用于L-硒-甲基硒代半胱氨酸产品及其制品质量的监控。     

手性柱高效液相色谱拆分测定营养强化剂硒-甲基硒代半胱氨酸对映体

目的:建立营养强化剂硒-甲基硒代半胱氨酸对映体拆分与定量测定高效液相色谱法,为其质量标准的建立奠定基础。方法:采用配体交换手性柱,以硫酸铜为手性配体流动相,考察了铜离子浓度、D,L-硒-甲基硒代半胱氨酸进样量和柱温等因素对硒-甲基硒代半胱氨酸对映体的拆分效果。结果:优化拆分条件为:检测波长240nm,柱温为35℃,流动相硫酸铜浓度为0.4mmol/L,流速为1.0mL/min。在上述色谱条件下,L-硒-甲基硒代半胱氨酸的进样量在0.95μg³0.28μg范围内与峰面积之间呈现良好线性关系,线性回归方程为Y=725.52X-62.13,R=0.9999,加标回收率为97.67%30.28μg范围内与峰面积之间呈现良好线性关系,线性回归方程为Y=725.52X-62.13,R=0.9999,加标回收率为97.67%⁹9.88%,检测限和定量限分别为0.0528μg和0.132μg。归一化法测得该色谱条件下能准确检出0.6%以上的D型异构体。结论:该方法专属性强,灵敏度较高,重现性好,结果准确,适用于L-硒-甲基硒代半胱氨酸的工艺和质量控制。     

硒与老鹰茶黄酮复配对山茶油的抗氧化效果

为了促进天然抗氧化剂的开发,以过氧化值为指标,以硒代蛋氨酸、甲基硒代半胱氨酸、亚硒酸钠和老鹰茶黄酮(HTTF)为研究对象,采用Schaal烘箱法对比单独和复配使用对山茶油的抗氧化效果。结果表明：硒代蛋氨酸、甲基硒代半胱氨酸和亚硒酸钠对山茶油均有抗氧化效果,且加入量越高,抗氧化效果越好;硒代蛋氨酸和亚硒酸钠与HTTF复配对山茶油的抗氧化效果均优于各单一组分,而甲基硒代半胱氨酸与HTTF复配对山茶油的抗氧化效果优于HTTF,但逊于甲基硒代半胱氨酸;硒代蛋氨酸、甲基硒代半胱氨酸、亚硒酸钠和HTTF单独使用和复配使用对山茶油的抗氧化效果均弱于TBHQ。综上,不同的硒与HTTF复配对山茶油的抗氧化效果不同。     

富硒玉米蛋白水解物中硒肽及含硒氨基酸的结构鉴定

为了明确硒在玉米蛋白中的赋存形式,采用高效液相色谱-质谱联用法(HPLC-MS/MS),结合质谱数据库比对以及高效液相色谱-等离子体质谱法(HPLC-ICP/MS),对富硒玉米蛋白水解物中硒肽及含硒氨基酸的结构进行鉴定。结果确定了5个小肽,其氨基酸序列分别为:SeMet-MeSeCys-Glu、Met-MeSeCys-Glu、MeSeCys-Glu-Asp、Ile-MeSeCys-Glu、γ-Glu-MeSeCys;确定了4种含硒氨基酸,分别为硒代蛋氨酸(SeMet)、硒代乙硫氨酸(SeEt)、L-硒-甲基硒代半胱氨酸(MeSeCys)、硒代胱氨酸(SeCys2)。借助于标样对含硒氨基酸和二肽进行定量,5个硒肽均含MeSeCys,其中只有一个肽段含SeCys2;但在含硒氨基酸中则是以SeMet含量最高为(586.3±49.5)ng/g,最低的是SeCys2为(102.6±9.0)ng/g。     

富硒大米中不同溶解性硒蛋白理化特性和抗氧化活性

目的:以富硒大米中不同溶解性的硒蛋白为研究对象,研究了其理化特性和抗氧化活性。方法:采用Osborne分级分离法从富硒大米中制备水溶性硒蛋白（WSP）、盐溶性硒蛋白（SSP）、醇溶性硒蛋白（ESP）和碱溶性硒蛋白（ASP）,对比其蛋白含量、总硒含量和硒蛋白的亚基分子量分布,通过紫外、红外光谱分析确定其特征官能团,并采用液相色谱-质谱联用法分析其硒代氨基酸组成等理化特性;在此基础上进一步分析了各类大米硒蛋白的抗氧化活性。结果:在4种不同溶解性的大米硒蛋白中,ASP具有最高的蛋白含量和硒含量（P<0.05）,且以小分子蛋白为主。ASP中存在3种硒代氨基酸,包括硒代半胱氨酸（300.22 ± 6.88 μg/kg）、甲基硒代半胱氨酸（170.19 ± 2.87 μg/kg）及少量硒代甲硫氨酸。大米硒蛋白的总抗氧化能力（T-AOC）、DPPH自由基清除能力与样品浓度呈良好的量效关系;在相同浓度下,不同大米硒蛋白的T-AOC、DPPH自由基清除能力的强弱顺序均为ASP>WSP>SSP。通过抗氧化活性与硒含量之间的相关性分析,两者之间存在极显著的正相关性（P<0.01）。结论:ASP是进一步纯化和研究较为理想的富硒大米提取物。     

硒蛋白生理功能研究综述

硒是一种必需微量元素,广泛存在于生物体内.硒蛋白是硒在生物体内实现生理功能的主要载体,是一类含硒代半胱氨酸的蛋白质.硒代半胱氨酸主要位于氧化还原催化位点,具有更高的氧化还原电位.在动、植物体内,硒蛋白主要以氧化还原酶的形式存在,具有调节细胞氧化应激、免疫功能、内质网应激和炎症反应等生物功能特性,对克山病、癌症、阿尔兹海...     

不同形态硒与VE联用对H_2O_2诱导人脐静脉血管内皮细胞氧化应激损伤的保护作用

目的:研究不同形态硒化合物(有机硒:L-硒甲基硒代半胱氨酸;无机硒:亚硒酸钠)单独使用及其与VE联合使用后对H_2O_2诱导人脐静脉血管内皮细胞(human umbilical vein endothelial cells,HUVECs)产生氧化应激损伤的保护作用。方法:采用体外细胞培养方法,将HUVECs随机分为7组:对照组、H_2O_2组、L-硒甲基硒代半胱氨酸(L-Se-methylselenocysteine,L-Se MSC)组、亚硒酸钠(sodium selenite,SS)组、VE组、L-Se MSC+VE联用组、SS+VE联用组。经不同样品干预处理后,采用四甲基偶氮唑蓝(methyl thiazolyl tetrazolium,MTT)法检测HUVECs存活率;检测各组细胞内脂质氧化终产物丙二醛(malondialdehyde,MDA)含量以及超氧化物歧化酶(superoxide dismutase,SOD)、谷胱甘肽过氧化物酶(glutathione peroxidase,GSH-Px)活性的变化。结果:各处理组HUVECs存活率之间没有显著差异;与H_2O_2组比较,0.1 mg/L亚硒酸钠、10 mg/L VE处理能使HUVECs内MDA生成量显著减少,SOD和GSH-Px活性显著升高,并且亚硒酸钠和VE联合使用在细胞水平上具有显著的协同作用,而L-Se MSC组与对照组无显著差异。结论:亚硒酸钠和VE均可保护由H_2O_2诱导引起的HUVECs氧化损伤,提高HUVECs抗氧化能力,并且亚硒酸钠和VE联用具有明显的协同抗氧化作用。     

硒代半胱氨酸生物合成研究进展

硒代半胱氨酸是蛋白质中硒的主要存在形式,也是多种有机硒化物的前体物质,在硒蛋白的合成中起到关键作用,在合成高活性硒化物,生产富硒食品,医药保健方面有着巨大潜力。该文探讨了硒代半胱氨酸的生物合成,总结了硒代半胱氨酸的检测提取方法,并比较了各类检测方法的优缺点。介绍了硒代半胱氨酸的微生物发酵生产方法及其在合成高活性硒化物中的应用,以期为今后的硒代半胱氨酸研究提供参考。     

反相高效液相色谱法测定富硒脱水菜心中的硒代氨基酸

建立了柱前衍生反相高效液相色谱-紫外检测富硒脱水菜心中硒代胱氨酸(SeCys)、硒甲基半胱氨酸(SeMeCys)和硒代蛋氨酸(SeMet)的方法,优化了样品预处理方法,并评价其定量分析的线性、准确性、重复性和检出限,结果显示:以0.1mol/LHCl为提取溶剂,超声处理8h,提取效果最佳;3种硒代氨基酸的平均加标回收率为95.7%～112.9%;在各硒代氨基酸的线性范围内,线性关系良好(R>0.999);保留时间和峰面积重复性的相对标准偏差(RSD)均分别低于2.0%和5.0%;酸性条件下的检出限为0.004～0.009mg/L。     

反向离子对高效液相色谱-电感耦合等离子质谱联用分析富硒食品中硒的形态

建立了利用反向离子对高效液相色谱-电感耦合等离子质谱(RP-HPLC-ICP-MS)联用分离检测富硒食品中硒酸根(SeO42-)、亚硒酸根(SeO32-)、硒代胱氨酸(SeCys2)、硒甲基硒代半胱氨酸(MeSeCys)、硒代蛋氨酸(SeMet)5种不同硒元素形态的方法。研究采用胰蛋白酶、蛋白酶K和链霉蛋白酶在Tris-HCl缓冲液中37℃条件下振荡酶解36h提取食品中的硒化物,利用Hypersil GOLD C8作为分离柱,磷酸二氢钾-七氟丁酸-甲醇-水体系作流动相,实现了在800s内完成5种硒元素形态的快速分离,分离效果好。再运用电感耦合等离子质谱(ICP-MS)检测5种硒化物,5种硒化物标准曲线线性良好,5种硒化物检出限分别为0.20,0.25,0.25,0.20,0.50μg/L,使用该方法实测标准样品回收率为100.6%。该方法分离效果好、检出限低,是一种有效可行的对富硒产品中硒元素形态的分析方法。     

表没食子儿茶素没食子酸酯分子修饰及抗癌研究进展

表没食子儿茶素没食子酸酯((–)-epigallocatechin-3-gallate,EGCG)是茶叶中的一类重要儿茶素,在体内外实验中被证实具有广泛的抗癌活性。研究发现,其抗癌机理包含诱导细胞凋亡、抗血管生成、调控细胞周期、阻滞细胞转移、协同抗癌等,但由于多羟基的化学结构使其在中性或碱性介质中极不稳定,最终导致其生物活性利用率降低,限制了临床应用范围。已有研究表明,分子修饰能显著改善EGCG分子活性,增强其稳定性,并使其表现出较强的抗癌活性。本文首先概述EGCG分子修饰的方法,然后对EGCG及其衍生物的抗癌实例和作用机理进行归纳总结。     

Vitamin E analogues as anticancer agents: lessons from studies with alpha-tocopheryl succinate

The new millennium has witnessed considerable decrease in a number of previously fatal pathologies, largely due to the advancement in molecular medicine and modern approaches to treatment. In spite of this success, neoplastic disease remains a serious problem due to several reasons. These include an exceedingly high variability of cancer cells even within the same type of tumour. Cancer cells, albeit of clonal origin, mutate so that they escape established treatments, resulting in the fatal outcome of current therapies. Moreover, there are types of cancer, such as mesotheliomas, that cannot be treated at present. A novel group of clinically interesting anticancer drugs has been a recent focus in the literature that hold substantial promise as selective anticancer drugs. These compounds, epitomised by alpha-tocopheryl succinate, comprise redox-silent analogues of vitamin E that have been shown to suppress several types of cancer in animal models, including breast, colon and lung cancer as well as mesotheliomas and melanomas, while being nontoxic to normal cells and tissues. It is now proven that the strong anticancer effect of vitamin E analogues stems from their propensity to induce selective apoptosis in malignant cells. The results point to the novel group of vitamin E analogues as promising agents applicable to different types of tumours.     

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.     

Limonoids as cancer chemopreventive agents

Nutritional research on the health benefits of substances in plant foods has recently advanced to a new stage. The research frontier has moved from study of classical vitamin deficiency diseases to study of the thousands of phytochemicals that may have important physiological effects. Recent research suggests that citrus fruit consumers may be getting another health benefit from orange juice and other citrus products called limonoids, which appear to possess substantial anticancer activity. Limonoids are highly oxidized triterpenes present in Rutaceae and Maliaceae families. Several citrus limonoids have recently been subjected to anticancer screening utilizing laboratory animals and human breast cancer cells. The experimental results described that citrus limonoids may provide substantial anticancer actions. The compounds have been shown to be free of toxic effects in animal models, so potential exists for the use of limonoids against human cancer in either natural fruits, in citrus fortified with limonoids, or in purified forms of specific limonoids. Although the initial studies are very promising they have been conducted primarily with in vitro cell culture and animal models. Thus, research is needed to determine whether the limonoids may be useful in preventing or treating cancer in humans. Copyright © 2005 Society of Chemical Industry     

柑橘果实中抗癌活性物质的研究现状和前景

从柑橘果实中 (幼果、果皮、果汁、种子 )提取分离具有抗癌药理作用的活性物质 ,在国内外受到关注。研究表明 ,至少在 3大类物质中即类胡萝卜素 (carotenoid)、黄酮类化合物(flavonids)及柠檬苦素类 (limonoids)的抗癌作用已被评价 ,其中从上述 3类物质中分离获得并鉴定的番茄红素 (lycopene)、柑橘苷配基 (naringenin)和柠檬苦素 (limonin)等 9种活性物质具有抗癌作用 ,β 胡萝卜素 (β carotene)可能对艾滋病有预防作用 ,更支持了上述的评价。     

表没食子儿茶素没食子酸酯的抗癌机制的研究进展

表没食子儿茶素没食子酸酯(epigallocatechin gallate,EGCG)是茶叶中主要的活性成分之一,具有抗氧化、抗炎症、抗癌等生理功效。在癌症的治疗和预防研究中,研究者将EGCG作为一种高效的天然化学预防剂,并期望将EGCG开发为保健食品和药品。本文就近年来国内外对EGCG抗癌活性、抗癌机理(抗氧化、抑制血管生成、诱导癌细胞周期阻滞、诱导癌细胞凋亡、抗炎症)方面的研究工作进行概述;并就当前EGCG在抗癌方面存在的缺陷提出解决方案和可实行的改进技术措施。      

薯蓣皂苷的抗癌机制研究进展

研究表明薯蓣皂苷具有良好的抗癌活性,可通过参与线粒体途径和死亡受体途径,对活性氧、B淋巴细胞瘤-2基因家族、细胞周期的调控,对信号通路、相关酶类的调节及细胞分化诱导等方面诱导细胞凋亡,从而起到抗癌作用。本文从薯蓣皂苷逆转多药耐药性、抗炎症作用、基质金属蛋白酶的表达、对表皮生长因子的影响及抑制血管生成等方面阐述薯蓣皂苷的抗癌作用机制,最后对其应用发展前景进行展望,以期为薯蓣皂苷作为抗癌药物的开发提供理论依据。     

白藜芦醇及其生物工程表达系统的研究进展

白藜芦醇是一种天然的植物保护素,它是许多植物受到真菌感染、紫外照射或病理状况下产生的一种植物抗毒素,可以提高植物抵抗病原体的能力,并且它也具有相当的生理活性,不但具有抗氧化、抗菌、调节血脂、抗癌的保健功能,而且研究证明白藜芦醇对于多种动物有延长寿命的功效。白藜芦醇在葡萄中的合成路径以及相关各酶的研究已经取得较好的进展。更重要的是,随着生物工程技术的发展,在植物、动物和微生物中合成白藜芦醇合酶的产物已不再困难。通过对近年来在不同表达系统中合成白藜芦醇的研究进行综述,提出利用生物工程技术来合成白藜芦醇所面对的问题及将来的发展方向。     

Rosemary and cancer prevention: preclinical perspectives

Colorectal cancer is the second leading cause of cancer death in Australia. Nutrition, particularly intake of vegetables and certain plant components, has been reported to have a major role in cancer risk reduction. Recently, there has been a growing research interest in rosemary, a common household plant grown in many parts of the world. This study aims to review scientific evidence from all studies, published from 1996 to March 2010 that examined the protective effects of rosemary on colorectal cancer and other types of cancer. Literature evidence from animal and cell culture studies demonstrates the anticancer potential of rosemary extract, carnosol, carnosic acid, ursolic acid, and rosmarinic acid. No evidence for other rosemary constituents was found. The reported anticancer properties were found to arise through the molecular changes in the multiple-stage process of cancer development, which are dose related and not tissue or species specific. This is evidenced by the ability of rosemary to suppress the development of tumors in several organs including the colon, breast, liver, stomach, as well as melanoma and leukemia cells. The results suggested that the different molecular targets modulated by rosemary and its active constituents are useful indicators of success in clinical cancer chemo-prevention trials.