制药工程专业英语第6单元逐句详解.doc

WORD格式 整理分享 专业资料 PART 2 BIOCHEMICAL PHARMACEUTICALS 生化制药 Unit 6 Isolation of Caffeine from Tea 从茶叶中分离咖啡因 In this experiment, Caffeine will be isolated from tea leaves. 在这个实验中，咖啡因会从茶叶中分离出来。 The major problem of the isolation is that caffeine does not occur alone in tea leaves, but is accompanied by other natural substances from which it must be separated. 分离过程中的主要问题就是，茶叶中不仅仅只有咖啡因，还伴随着需要被分离除去的其他天然物质。 The major component of tea leaves is cellulose，which is the major structural material of all plant cells. 茶叶中的主要成分是所有植物细胞中的主要结构材料——纤维素。 Cellulose is a polymer of glucose. 纤维素是葡萄糖的聚合物。 Since cellulose is virtually insoluble in water, it presents no problems in the isolation procedure. 然而纤维素实际上是不溶于水的，所以在隔离的程序上不用考虑去除纤维素。 Caffeine, on the other hand, is water soluble and is one of the major substances extracted into the solution called tea”. 另一方面，咖啡因是水溶性的，也是萃取到溶液（也就是茶）里的主要物质之一。 Caffeine comprises as much as 5 percent by weight of the leaf material in tea plants. 咖啡因包含了茶树叶片材料总重的5%之多。 Tannins also dissolve in the hot water used to extract tea leaves. 丹宁（鞣酸）也溶解于用于萃取茶叶的热水中。 The term tannin does not refer to a single homogeneous compound, or even to substances which have similar chemical structure. 丹宁一词不是指单个均一的化合物，也不是具有相似化学结构的物质。 It refers to a class of compounds which have certain properties in common. 它是指某些具有共同属性的化合物的种类。 Tannins are phenolic compounds having molecular weights between 500 and 3000. 丹宁是一类分子质量在500到3000的含酚的化合物。 They are widely used to tan” leather. 它们被广泛用于鞣革。 They precipitate alkaloids and proteins from aqueous solutions. 它们从水溶液中沉淀出生物碱和蛋白质 Tannins are usually divided into two classes: those which can be hydrolyzed and those which cannot. 丹宁通常被分为两类：可水解和不可水解。 Tannins of the first type which are found in tea generally yield glucose and gallic acid when they are hydrolyzed. 在茶中，第一类丹宁水解后通常产生葡萄糖和五倍子酸。 These tannins are esters of gallic acid and glucose. 这些丹宁是五倍子酸和葡萄糖的酯类。 They represent structures in whic