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wfwsgv铁杆木虫 (正式写手)
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求翻译一段英文成中文
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Flavonoids are a large group of structurally related compounds with a chromane-type skeleton, with a phenyl substituent in the C2 or C3 position. The main flavonoid subclasses are depicted in Fig. 1. Flavonoids are often hydroxylated in positions3, 5, 7, 3’, 4’ and/or 5’. Frequently, one or more of these hydroxyl groups are methylated, acetylated, prenylated or sulphated. In plants, flavonoids are often present as O- or C-glycosides; O bonding in flavonoids occurs far more frequently thanCbonding. TheO-glycosides have sugar substituents bound to a hydroxyl group of the aglycone, usually located at position 3 or 7, whereas the C-glycosides have sugar groups bound to a carbon of the aglycone, usually 6-C or 8-C. The most common carbohydrates are rhamnose, glucose, galactose and arabinose. Flavonoid-diglycosides are also frequently found. Two very common disaccharides contain glucose and rhamnose, 1→6 linked in neohesperidose and 1→2 linked in rutinose. The sugars are often further substituted by acyl residues such as malonate and acetate [1]. Flavonoids are referred to as glycosides when they contain one or more sugar groups (or glucosides in case of a glucose moiety), and as aglycones when no sugar group is present. Flavonoid classification and nomenclature are not always straightforward, therefore, of the flavonoids discussed in the paper the structure can be derived from Fig. 1. Throughout the paper the most common trivial names are used. Given the above structural variety, it will come as no surprise that there is an extremely large number of flavonoids.Typical quotations include “>4000 known flavonoids comprising 12 subclasses” [2], “more than 3000 flavones and more than 700 known isoflavones exist in plants” [3] and “almost 6500 different flavonoids are known” [4]. Consequently, the separation, identification and trace-level determination of flavonoids is challenging. They receive considerable attention in the literature, specifically because flavonoids are of biological and physiological importance. Flavonoids are one of the largest groups of secondary metabolites, and they play an important role in plants as defence and signalling compounds in reproduction, pathogenesis and symbiosis [5,6]. Plant flavonoids are involved in response mechanisms against stress, as caused by elevatedUV-B radiation [7–10], infection by microorganisms [11] or herbivore attack [12]. Flavonoids are also involved in the production of root nodules as a nitrogen fixation system after infection by Rhizobium bacteria in a variety of leguminous plants [13] – theyare pigment sources for flower colouring compounds – [14] and play an important role in interactions with insects [15]. They also affect human and animal health because of their role in the diet, which is ascribed to their antioxidant properties [16] or their estrogenic action [17], and to a wide range of antimicrobial and pharmacological activities [18,19]. Many different enzymes involved in intracellular signalling can be affected by flavonoids.Especially, the effects of flavonoids on protein kinases are of great interest since they directly influence immune functions in the host [20]. The above described spectrum of functions explains why recently quite a number of reviews have been published on the properties of flavonoids [8,21–24] and on the state-of-the-art analysis of flavonoids (Table 1). An important aspect of flavonoid analysis is whether to determine the target analytes in their various conjugated forms or as the aglycones. In biological fluids (serum, plasma and urine) flavonoids exist as glucuronide and sulphate conjugates. In most cases, only the total aglycone content is determined; therefore, a hydrolysis step is used. However, in plants, medicine and food products, researchers are usually interested in the intact conjugates.For example, for the classification of plant species, intact flavonoid profiles in plants are determined [25–27]. In that case, analyses become much more complicated, because the number of target analytes increases significantly: much more selective and sensitive analytical methods are now required. In Fig. 2 the principal strategies for the determination of flavonoids in biological fluids, drinks, plants and food – the main sample types – are schematically depicted. The various steps in this flow chart will be considered in some detail below, with attention to both routine procedures and recent developments. Of course, in view of the complexity of the problem (almost) all analytical methods dealing with flavonoids include a high-performance separation method. The choice of the method depends on the sensitivity required for the purpose at hand, the complexity of the biological matrix – which is related to the time spent on sample pretreatment prior to analysis – the required chromatographic resolution and the preferred detection method. To give a general indication of the attention devoted to flavonoid analysis in the last 5 years, over 300 papers were written on the analysis of plants, mainly to characterize and quantify their constituents for medicinal or taxonomical reasons. Most reviews listed in Table 1 also deal with the determination of flavonoids in plants. A further 50 papers reported on the analysis of human and animal body fluids. The main goal of these studies was to monitor flavonoid metabolism. Some 30 papers and several reviews (cf. Table 1) were devoted to the analysis of flavonoids in food and drinks, in most cases to determine their anti-oxidant activity and, in the case of juices, also to check them for possible adulterants. As was already briefly indicated above, the present review intends to discuss the determination of a wide variety of flavonoids – aglycones as well as conjugates – in many different sample types by means of routine or more recently developed analytical techniques. In all instances, selected real-life applications will be included to illustrate the practicability, and the scope and limitations of the various approaches. Because of the increasing interest in structure elucidation of flavonoids,special attention will be devoted to the use of tandem-mass spectrometric (MS/MS) techniques for the characterization of several important sub-classes, and to the potential of combined diode-array UV (DAD UV), tandem-MS and nuclear magnetic resonance (NMR) detection for unambiguous identification. The structures of the main flavonoids discussed in the following sections are listed in Fig. 1. 时间比较忙，请大家帮帮忙 Sample Text |
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melody-yhl
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wfwsgv(金币+35, 翻译EPI+1):大部分挺好的，谢谢美女啊 2010-04-20 21:49
| 类黄酮是一大群与色满型构架结构相关的化合物，在C2或C3位置具有一苯基取代基。主要的类黄酮亚纲描绘在第1图中。类黄酮通常在3、5、7、3’、4’及/或5’位置处被羟基化。常常，这些羟基的一或多个被甲基化、乙酰化、异戊二烯化或硫酸盐化。在植物中，类黄酮通常作为O-苷或C-苷而出现；在类黄酮中，O结合出现的远比C结合更频繁。氧苷具有结合至糖苷配基的羟基的糖取代基，通常位于位置3或位置7处；然而，C苷具有结合至糖苷配基的碳的糖基团，通常为6-C或8-C。最常用的碳水化合物为鼠李糖、葡萄糖、半乳糖及阿拉伯糖。类黄酮-双糖苷也很常见。两个极普通的二糖含有葡萄糖和鼠李糖，新橙皮糖为1→6键，而芸香糖中为1→2键。这些糖通常进一步由诸如丙二酸盐及醋酸盐的酰基残基取代[1]。在类黄酮含有一或多个糖基团时,称其为苷（或在为葡萄糖一半的情况下称为糖苷），且在不存在糖基团时称为糖苷配基。类黄酮分类及命名并不总是直接的，因此，论述于论文中的类黄酮结构可来源于第1图。全论文使用最常用的俗名。考虑到上述结构种类，无疑将存在非常多的类黄酮。典型的报价单包括“>4000种包含12个亚纲的已知类黄酮"[2],“多于3000种黄酮和多于700种已知异黄酮存在于植物中"[3]，且“几乎6500种类黄酮为已知的”[4]。因此，类黄酮的分离、鉴定和微量测定是一种挑战。在文献中，它们受到相当大的注意，特别因为类黄酮的生物学和生理学的重要性。类黄酮是次级代谢产物的最大群组之一，且它们在繁殖、发病机理和共栖中作为防卫及信号化合物而起着重要作用[5,6]。当由上升的UV-B辐射引起时，植物类黄酮涉及抵抗应力、微生物传染[11]或草食动物攻击[12]之反应机制。在各种豆科植物中，类黄酮也涉及根瘤的生产，在根瘤菌感染以后作为固氮作用系统[13]-它们是花着色化合物颜料源[14]且在与昆虫相互作用中起重要作用[15]。因为在饮食中的作用，它们也影响人类和动物健康，这归于其抗氧化剂性能[16]或其雌激素作用[17]，和其广泛的抗菌及药理学的活性[18,19]。涉及胞内信号的许多不同酶可受类黄酮的影响。尤其，类黄酮对蛋白激酶的影响令人感兴趣的，因为其直接影响宿主的免疫功能[20]。上述功能范围解释了近来发表相当多关于类黄酮性能[8,21–24]和关于类黄酮的先进技术分析（表1）的综述的原因。类黄酮分析的一个重要方面不是确定其各种共轭形成物中的目标分析物就是作为糖苷配基。在生物流体（血清、血浆和尿）中，类黄酮作为葡糖苷酸和硫酸盐共轭物而存在。在大多数情况下，仅确定总的糖苷配基含量；因此，使用水解步骤。然而，在植物、医学和食品产品中，研究人员通常未损伤的共轭物感兴趣。举例而言，对于植物品种分类，植物中的未损伤的类黄酮概况经确定[25–27]。那样的话，分析变得更加复杂，因为目标分析物的数目显著地增加：现需要更精选和更敏感的分析方法。在第2图中，用示意图描绘了用于确定主要样品类型-生物流体、饮料、植物和食物中的类黄酮的主要策略。此流程图中的各步骤在下文中将被认为相当详细地，注意常规程序和近期发展。s当然，鉴于该问题之复杂性，（几乎）所有处理类黄酮的分析方法包括高性能分离方法。方法的选择取决于眼前目标要求的敏感性、生物基质的复杂性-其与在分析以前耗费在样品预处理上的时间相关-需要的色谱分离和较佳检测方法。在过去的5年里，为给出致力于类黄酮分析的注意的一般指示，超过300篇论文撰写了关于植物的分析，主要处于医学和分类学的原因表征和定量其成分。列于表1中的大多数综述也涉及植物中的类黄酮确定。其他50篇论文报告了关于人和动物体液的分析。这些研究的主要目标是监测类黄酮新陈代谢。大约30篇论文和数篇综述致力于食品和饮料中的类黄酮分析，大多数情况下是确定其抗氧化活性，且就果汁来说，也检查其可能的掺杂物。如上文已简要地指出，本综述意欲借助于常规和最近发展的分析技术来确定许多不同样品类型中的各种各样的类黄酮-糖苷配基以及共轭物。在一切情况下，为说明实用性和各种方法的范畴及限制，已选择的现实应用将被包括。因为在类黄酮的结构解析方面正增加的兴趣，特别的注意将致力于串联-质谱仪（MSMS）技术的使用，用于表征若干重要亚纲，并致力于联合二极管阵列UV(DADUV)、用于明确鉴定的串联MS及核磁共振（NMR）检测的潜在性。在以下几节里讨论的主要类黄酮的结构列于第1图中。 |
5楼2010-04-20 16:06:36
★ ★
sirljz(金币+2):谢谢交流 2010-04-20 14:33
wfwsgv(金币+5):谢谢参与 2010-04-20 21:50
sirljz(金币+2):谢谢交流 2010-04-20 14:33
wfwsgv(金币+5):谢谢参与 2010-04-20 21:50
| 黄酮类化合物是一类大基团与chromane型骨架结构相连的化合物，在C2或C3位位置被苯基取代。主要的子类黄酮在图1中被描绘。羟基黄酮类化合物往往在3，5，7，3'，4'和/或5'位被羟基甲基化。通常，一个或多个羟基甲基化，乙酰化或硫酸。在植物中，黄酮类化合物通常为O或C -苷型，在目前黄酮类化合物中O-键发现的频率远高于C-键。配糖类的氧键发生在糖苷配基的羟基取代通常发生的3或7位，配糖类的碳键发生在糖苷配基的羟基取代通常发生的6或8位。最常见的碳水化合物鼠李糖，葡萄糖，半乳糖和树胶醛糖。 |
2楼2010-04-20 10:09:59
3楼2010-04-20 10:11:18
wfwsgv
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4楼2010-04-20 10:27:27