Chemistry of Flavonoids
Chemistry of Flavonoids
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DOI：
10.1002/9780813809397.ch5
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发表时间：
2009-12
期刊：
影响因子：
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通讯作者：
R. Tsao;J. Mccallum
中科院分区：
文献类型：
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作者：
R. Tsao;J. Mccallum
香精是植物界中最丰富的天然产物之一。虽然术语“类黄酮”已被许多人，包括研究人员，与其他术语如“多酚”，“多酚”或“酚类”互换使用，但本书的读者有必要明确区分这些术语。多酚或多酚类化合物是植物化学物质的更广泛类别，包括酚酸、芪、类黄酮和具有酚特征的其他植物化学物质。水果和蔬菜中的大多数“酚类”是多酚类（苯环上有> 1个羟基）。黄酮通常具有共同的C6-C3-C6黄酮骨架，其中苯基之间的三碳桥通常被氧包围。根据三碳链段（C环）的不饱和度和氧化程度，类黄酮进一步分为几个亚类（图5.1）。文献中报道的大多数类黄酮是相对少量的类黄酮苷元的糖苷，其通常是水溶性的并积累在植物细胞的液泡中（Bohm 1998; Seigler 1998）。B环的结构特征以及黄酮骨架的所有A、B和C环上的羟基化和糖基化模式使黄酮类化合物成为最大和多样的植物化学基团之一。类黄酮的确切数量很难知道;然而，据报道，其数量在2，000至6，500之间（Harborne和威廉姆斯2000; Klejdus等2001; Rauha等2001; Tsao和Deng 2004; de Rijke等2006）。这些化合物通常作为植物中的色素来吸引传粉者，或者作为植物对入侵昆虫和微生物的化学防御。黄曲霉素可能参与其他生物相互作用。近年来一直在积极研究的一个重要作用是它们可能对人类健康有益。已发现黄酮类化合物具有有效的抗氧化活性（Pietta 2000）。越来越多的流行病学研究证据表明，富含黄酮类化合物的饮食对降低人类心血管疾病和癌症的风险有显着作用。出于这个原因，加拿大卫生部和美国食品和药物管理局都允许水果和蔬菜消费的健康声明，并降低心脏病和某些癌症的风险（加拿大卫生部在线; FDA-美国在线）。关于黄酮类化合物的健康益处的更详细的讨论可以在本书的第6章中找到。
Flavonoids are one of the most abundant natural product groups occurring in the plant kingdom. Although the term “flavonoids” has been interchangeably used by many, including researchers, with other terms such as “polyphenols,”“polyphenolics,” or “phenolics,” it is necessary for the readers of this book to make a clear distinction between these terms. Polyphenols or polyphenolics are a broader category of phytochemicals that includes phenolic acids, stilbenes, flavonoids, and other phytochemicals with phenolic features. Most “phenolics” in fruits and vegetables are polyphenolics (with> 1 hydroxyl group on a benzene ring). Flavonoids generally have a common C6-C3-C6 flavone skeleton in which the threecarbon bridge between the phenyl groups is usually enclosed with oxygen. Based on the degree of unsaturation and oxidation of the three-carbon segment (C-ring), flavonoids are further divided into several subclasses (Fig. 5.1). Most flavonoids reported in the literature are glycosides of a relatively small number of flavonoid aglycones, which are generally water-soluble and accumulated in the vacuoles of plant cells (Bohm 1998; Seigler 1998). The structural features of the B-ring and the hydroxylation and glycosylation patterns on all A, B, and C rings of the flavone skeleton have made flavonoids one of the largest and diverse phytochemical groups. The exact number of flavonoids is difficult to know; however, it has been reported to be anywhere from 2,000 to 6,500 (Harborne and Williams 2000; Klejdus and others 2001; Rauha and others 2001; Tsao and Deng 2004; de Rijke and others 2006). These compounds frequently serve as pigments in plants to attract pollinators, or as plants’ chemical defense against invading insects and microorganisms. Flavonoids may have been involved in other biological interactions. A significant role that has been under active research in recent years is their possible health beneficial effects to humans. Flavonoids have been found to possess potent antioxidant activities (Pietta 2000). Increasing evidence from epidemiological studies suggests that diets high in flavonoids are contributing significantly to lower risks of cardiovascular diseases and cancer in humans. For this reason, both Health Canada and the US Food and Drug Administration have allowed health claims for fruit and vegetable consumption and lowered risks of heart diseases and certain cancers (Health Canada online; FDA-USA online). More detailed discussions on the health benefit of flavonoids can be found in Chapter 6 of this book.