【作者】 戚丽；

【导师】 张正竹；

【作者基本信息】 安徽农业大学 ， 茶学， 2008， 硕士

【摘要】 糖苷,是糖或糖的衍生物与另一类非糖物质通过糖的端基碳原子链接而成的化合物。有机分子和糖结合形成糖苷后,由于糖基团的亲水性和苷元基团的亲脂性而以两性在植物体内存在,不具有苷元的生理活性,且更加稳定。茶树叶片中不仅含有游离态的芳香族醇及单萜烯醇,还存在丰富的芳香族醇和单萜烯醇糖苷,茶鲜叶在采摘,水分亏损,叶片损伤和感菌等胁迫环境下,糖苷类物质容易酶解释放苷元,这些以单萜烯醇和芳香族配基为主的香气前体类物质水解后,苷元呈现花果香是构成茶叶香气品质的物质基础。从茶鲜叶中提取的糖苷类香气前体物质,用茶叶粗酶水解后,气相色谱分析挥发性的酶解产物,定性和定量结果表明,顺-3-己烯醇、芳樟醇氧化物、芳樟醇、水杨酸甲酯、香叶醇、苯甲醇和苯乙醇是水解后挥发性苷元的主要成分,且挥发性苷元含量远高于茶叶中相应的游离态香气。茶叶糖苷类香气前体和游离态香气组分对茶树叶部主要致病真菌(茶云纹叶枯病菌、茶轮斑病菌、茶赤叶斑病菌、茶炭疽病菌)均具有显著的抑菌作用。体外抗菌实验结果表明,在浓度为5.0-25.0mg/mL之间,茶叶糖苷类香气前体对四种致病真菌表现出显著的抑制作用;在浓度为100-2000μg/mL之间,茶叶游离态香气组分也对四种致病真菌表现出不同程度的抑制作用,其中香叶醇抑制作用最强。茶多酚被认为有广谱抗菌性,但对这四种病原真菌没有明显的体外生长抑制作用,其体外抗菌实验结果表明,EGCG(表没食子儿茶素没食子酸酯)和茶多酚在浓度高达80mg/mL时对这四种病原菌没有表现出生长抑制作用。在这三种物质中,游离态香气和糖苷类香气前体组分浓度与抗菌活性呈正相关。在病原真菌的培养液中检测到β-葡萄糖苷酶活性并能水解茶叶糖苷类香气前体,验证了在糖苷类香气前体体外抑菌实验中,其抑菌作用是由于病菌释放的水解酶产生的苷元来实现的。由此推测,具有抑菌作用的游离态香气以稳定的糖苷类香气前体形式贮存在茶树叶片中,当遇到病菌侵染时,在内源葡萄糖苷酶和外源病原菌水解酶的作用下,水解并释放出挥发性苷元,从而表现出抗病性。挥发性苷元在抗病防御体系发挥作用的同时也对茶树香气品质有促进作用,这对培育高香和强抗病性茶树品种有一定借鉴意义。更多还原

【Abstract】 Glycosides are certain molecules in which a sugar part bound to some other part through its anomeric carbon to another group.Glycosides play important role in living organisms, many plants store important chemicals in the form of inactive glycosides for its stability. Not only much monoterpene alcohols and aryl alcohols in tea leaf,but also significant amount of glycosidically bound form volatiles are accumulated in the leaves of Camellia sinensis(L.) O.Kuntze with monoterpene alcohols and aryl alcohols as the major aglycones,these aglycones will be released from their respective glycosides by endogenous enzymatic hydrolysis under the conditions of leaf plucking,tissue damage, pest damage and malady infection etc.,the released volatiles aglycones are the basic part of tea aroma.A crude glycosides was extracted from fresh tea leaves and treated with the crude tea enzyme,cis-3-hexenol,linalool oxides,linalool,methyl salicylate,geraniol,benzyl alcohol and phenylethanol were monitored to be the major aglycone moieties by gas chromatography analysis.Quantitative and qualititative analysis showed that the amounts of the aglycone moieties of glycosides were higher than relative compounds in free form.Both the glycosidic aroma precursors and free form tea aroma components exhibited inhibitive activities against tea leaf pathogenic fungi(Phyllosticta theicola petch, Pestalozzia theae Sawada,Gloeosporium theae-sinensis Miyak,Colletotrichum Camelliae Massee)obviously in vitro.Glycosidic aroma precusors exhibited inhibitive activities during concentration between 5.0 mg/mL to 25.0 mg/mL in Potato Dextrose Agar(PDA) culture medium,free tea aroma components exhibited different inhibitive activities during the concentration between 100μg/mL to 2000μg/mL in PDA culture medium,geraniol shown the strongest inhibitive activity in seven volatiles.Tea polyphenols were widely believed as substance possess wide range of antibacterial while was evaluated no inhibitive activity against choosed fungi,it shown no inhibitive activities as well as EGCG(ep igallo-catechin gailate) even up to the highest concentration 80 mg/mL in PDA medium.Among the three kinds of major tea leaf components,the free form tea aroma and glycosides aroma precursor componets revealed positive correlation with tea leaf pathogenic fungi resistance.The activity ofβ-glucosidase was detected in liquid culture medium of pathogenic fungi, and the glycosidic aroma precursors was hydrolyzed by the germinated enzymes,in vitro antifungal test of glycosides,it proved that the antifungal effect is due to the release of the aglycone to achieve.Therefore,it was deduced that the free aroma are formed and stored as glycosides in the intact tissue of tea leaf and hydrolyzed by the actions of both the endogenous and exogenous glucosidase to release volatiles as antifungal substances when exposed to fungi infection.The effect of free aroma on tea disease defense system and tea aroma,which provides a valuable tool for screening potential tea plant cultivar with higher aromatic quality and tea leaf diseases-resistance.更多还原