【作者】 杨静；

【导师】 朱祝军；

【作者基本信息】 浙江大学 ， 蔬菜学， 2009， 博士

【摘要】 硫代葡萄糖苷(β-thiogtucoside N-hydroxysulfates)是十字花科植物中一组重要的富含氮硫的阴离子次生代谢物质。过去，硫代葡萄糖苷通常作为重要的风味物质而存在。随着研究的深入，人们发现硫代葡萄糖苷还与植物的自我保护机制以及人类的身体健康有着非常密切的关系。因此，如何从十字花科芸薹属蔬菜中获得更多有益硫代葡萄糖苷已成为近几年的一个研究热点。硫代葡萄糖苷的种类主要是由植物自身基因型决定的，而含量还受到植株生长及周围环境条件的影响。同时，经过采收、贮藏和烹饪等一系列加工过程后，蔬菜硫代葡萄糖苷的含量将会受到影响，因为组织破坏导致硫代葡萄糖苷与葡糖硫苷水解酶(黑芥子酶)接触，从而造成硫代葡萄糖苷的水解。因此，研究生长条件、环境因素及不同的贮藏、烹饪方法对蔬菜硫代葡萄糖苷含量的影响，将具有重要的理论意义和应用价值。本文以起源于我国并且在长江流域栽培普遍的小白菜(Brassica campestrisL．ssp．chinensis)为试验材料，研究了氮、磷、镁、铁等营养元素对其生长和营养物质(主要是硫代葡萄糖苷)的影响，及不同贮藏条件和烹饪方法对小白菜硫代葡萄糖苷含量的影响。以期阐明不同营养状态(不同形态氮素及比例、磷、镁和铁)与光照强度对小白菜硫代葡萄糖苷含量的影响；采后措施(贮藏温度和烹饪方法)对硫代葡萄糖苷流失的影响。从而为小白菜的种植、贮藏和烹饪提出指导意见。具体如下：(1)采用营养液栽培的方式，研究了不同形态氮素比例对小白菜生长和硫代葡萄糖苷的影响。试验设置了5个比例浓度，分别是0：8、2：6、4：4、6：2和0：8(铵态氮：硝态氮)。结果表明，适当比例的铵态氮和硝态氮共同作为氮源(特别是铵态氮：硝态氮为2：6时)更有利于植株生长。铵态氮的使用可以明显降低小白菜地上部的硝酸盐含量。100％铵态氮供应时，硫代葡萄糖苷含量大幅增加。与此同时，植株生长受到很大抑制。(2)采用营养液栽培的方式，研究了不同磷浓度(1．00 mM，正常供磷：0．01 mM，缺磷)和光照强度(正常光照和60％遮荫)对小白菜生长和硫代葡萄糖苷的影响。结果表明，缺磷降低了植株地上部生物量、类胡萝卜素和叶绿素含量。在正常光照下植株生长比较好，但是类胡萝卜素和叶绿素的含量反而有所下降。这可能是因为本试验以干重为单位的缘故或者由植株生长的稀释效应引起的。缺磷或者正常光照处理时，小白菜植株的根冠比较大。缺磷处理还增加了植株单个和总硫代葡萄糖苷的含量，而且在正常光照条件下特别明显。较强光照对脂肪族硫代葡萄糖苷的合成有促进作用；对吲哚族硫代葡萄糖苷和芳香族硫代葡萄糖苷则没有显著的影响。另外，磷浓度和光照强度对硫代葡萄糖苷前体——氨基酸的含量也有较大影响，但是氨基酸浓度的变化和硫代葡萄糖苷含量之间不存在绝对的对应关系。(3)采用营养液栽培的方式，研究了不同镁浓度(1．00 mM，正常供镁：0．02 mM，缺镁)和光照强度(正常光照和60％遮荫)对小白菜生长和硫代葡萄糖苷的影响。结果表明，缺镁也不利于植株生长以及类胡萝卜素和叶绿素积累。缺镁对植株中不同种类硫代葡萄糖苷含量的影响是不同的。正常光照条件下，缺镁与脂肪族硫代葡萄糖苷的含量负相关，与吲哚族硫代葡萄糖苷的含量正相关，而对芳香族硫代葡萄糖苷的含量没有影响。在弱光条件下，镁离子浓度对硫代葡萄糖苷的含量没有明显影响。(4)采用营养液栽培的方式，研究了不同铁浓度(50μM，正常供铁；5μM，缺铁)和光照强度(正常光照和60％遮荫)对小白菜生长和硫代葡萄糖苷含量的影响。结果表明，无论在哪种光照条件下缺铁后植株生物量、类胡萝卜素和叶绿素含量都发生明显下降，而单个和总硫代葡萄糖苷的含量都呈上升趋势。同样，光照强度对植株硫代葡萄糖苷的含量有明显的影响并和供铁水平存在一定的互作效应。(5)研究了不同贮藏温度(20℃，常温；4℃，低温)对小白菜失重率、叶绿素、类胡萝卜素和硫代葡萄糖苷含量的影响。结果表明，低温贮藏对缓解小白菜类胡萝卜素(β-胡萝卜素和叶黄素)和叶绿素的损失，保持其外观品质以及硫代葡萄糖苷含量都是有利的。在试验结束时低温贮藏条件下植株的总硫代葡萄糖苷甚至还有些许的增加，主要是由5-甲亚磺酰戊基硫代葡萄糖苷、3-丁烯基硫代葡萄糖苷、4-戊烯基硫代葡萄糖和4-甲氧吲哚-3-甲基硫代葡萄糖苷的含量增加引起的。这可能是因为硫代葡萄糖苷合成的增加以及原来被束缚的化合物被释放而引起的。(6)比较了几种日常烹饪方法(烫漂、水煮、蒸、油炒和微波)对小白菜中硫代葡萄糖苷含量的影响。结果表明，烫漂后硫代葡萄糖苷的损耗量最小。其次是蒸、油炒和微波。水煮会导致一大部分硫代葡萄糖苷流失到汤汁中。由此可见，烫漂是一种可以尽量减少蔬菜中硫代葡萄糖苷损耗的理想烹饪方法，如果采用水煮法，最好连汤一起食用。更多还原

【Abstract】 Glucosinolates （β-thioglucoside N-hydroxysulfates, GSs） are nitrogen- andsulfur-containing anionic natural products, one group of plant secondary metabolitesfound in Cruciferae. Glucosinolates were well known because of the strong flavorsand tastes. In the past decade, glucosinolates have been identified as the self-defencecompounds for plants and cancer-prevention agents for human beings with in-depthstudy. Therefore, how to get more beneficial glucosinolates from these vegetables hasbecome a hot research topic in recent years.The profiles of glucosinolates are usually determined by genotypes, howeverglucosinolate contents are also affected by plant growth conditions and environmentalfactors. In the process of harvest, storage and cooking etc, the glucosinolates areeasily hydrolyzed into a variety of degradation products due to its contact withthioglucosidases [myrosinases （EC 3.2.3.1）] upon the plant tissue disruption. Theunsuitable postharvest treatments induce unnecessary loss of glucosinolates.Pakchoi （Brassica campestris L. ssp. chinensis var. communis）, a traditionalcruciferous vegetable originated from China, is widely grown in the Yangtze Riverregion. The effects of nitrogen （N） form, the supply levels of phosphorus （P）,magnesium （Mg） and iron （Fe）, storage temperature and cooking method on theprofiles and contents of bioactive compounds （such as GSs） are studied. So, it will beimportant to find the best nutrient composition, plant growth condition andprocessing method for the high content and good retention of glucosinolate inpakchoi. The main results as follows:（1） The effects of different N forms on GS contents were studied in pakchoi plantsgrown in nutrient solution. Five treatments with the same total N content （8 mM） but different ammonium/nitrate ratios were used (NH₄⁺-N: NO₃^?-N, 0:8, 2:6, 4:4, 6:2 and8:0). The highest plant biomass was achieved by mixed supply of both forms of N,especially in 25% ammonium-N supply. Nitrate accumulated at a lower level whennitrate-N was replaced with ammonium-N. GSs contents were higher whenammonium-N supplied than other treatments, however, the worse plants growth wasin an opposite way.（2） The effects of P supply levels （1.00 and 0.01 mM） and different lightintensities （normal and 60% shading） on plant growth and GSs contents wereinvestigated in pakchoi plants grown in nutrient solution. P deficiency decreasedshoot biomass and the pigments content. Plant could grow better whereas the pigmentcontent decreased under normal light intensity. That might because the values werebased on dry weight and/or a dilution effect in this case. P deficiency and high lightintensity increased the root/shoot ratio. P deficiency increased the contents ofindividual and total GSs content especially under normal light intensity. Higher lightintensity increased the content of aliphatic GS, however light supply has nosignificant effect on indolyl and aromatic GS, provided P supply was sufficient. Onthe other hand, the GS precursor - amino acid （AA） was also affected by differentlevels of P supply and light intensities. However, changes in the content of free AA donot result in altered GS contents.（3） The effects of Mg²⁺ levels （1.00 and 0.02 mM） and different light intensitieson plant growth and GSs content were studied in pakchoi plants grown in nutrientsolution. Mg²⁺ deficiency inhibited pakchoi plant growth and reduced pigmentsaccumulation. The influence of Mg supply was not uniform for different types of GSconsidered, as positive （indolyl GS）, negative （aliphatic GS）, and neutral （aromaticGS） effects under normal light intensity. However, the effect was not significantunder low light intensity. （4） Two treatments for Fe supply （50 and 5μM） were used. The results indicatethat Fe deficiency decreases the plant biomass and pigments content under both lightintensity conditions. However, GSs contents were increased. Light intensity affectedGS content obviously, and shown an interaction effect with Fe supply.（5） Influences of two temperatures （4 and 20℃） on weight loss, carotenoids andGS contents in pakchoi shoots were investigated during storage. The results suggestthat low temperature was beneficial to reduce the loss of carotenoids （β-carotene,lutein and chlorophylls） and maintained the visual quality as well as GS content oreven increased the content of total GS, specifically total aliphatic GS, and individualGS glucoalyssin, gluconapin, glucobrassicanapin and 4-methoxyglucobrassicin at theend of experiment. That could be due to the increased glucosinolate synthesis and/or arelease of bound compounds during storage.（6） The influences of common culinary proceeding （blanching, boiling, steaming,stir-frying and microwave） on GS profile and contents in pakchoi shoots weredetermined. Blanching retained the highest glucosinolate content. The data alsoshowed that the GS content was not reduced by steaming, stir-frying and microwavesignificantly. On the contrary, significant loss of GSs was resulted from boiling byleaching into cooking water. Aliphatic GS has a better thermal stability than indolyland aromatic GS. Therefore, the best cooking method for pakchoi to maintain higherGS content should be blanching, followed by steaming, stir-frying and microwave. Itis not good for health to throw away the cooking water when pakchoi was boiled inwater for a long time.更多还原