可可茶经栽培后化学成分的变化及其与传统茶的比较分析

野生茶树可可茶(Camellia Ptilophylla Chang)由于其芽叶中的嘌呤生物碱主要为可可碱,因而不同于传统茶叶。通过化学筛选,在纯种无性苗建立的可可茶基地上,随机进行单株取样,对可可茶的水浸出物、游离氨基酸、水溶性糖、茶多酚、儿茶素类、花青素、嘌呤生物碱等成分进行了检测。将这些结果与野生可可茶相关成份进行比较,发现可可茶经人工栽培后,含优势可可碱的特点保持不变,游离氨基酸总量和儿茶素类含量得到了明显的提高。进一步与传统茶叶比较后,得出两者之间的最大差异是可可茶含可可碱,不含咖啡碱;传统茶叶含咖啡碱为主,同时伴生相当于0．5～1％咖啡碱量的可可碱。     

苦茶Camellia assamica var.kucha茶多酚的HPLC-DAD/MS分析

苦茶是一种特殊的茶组植物,它以1,3,7,9-四甲基尿酸为主要的嘌呤生物碱。本文采用高效液相色谱-二极管阵列检测/质谱联用(HPLC-DAD/MS)的方法对苦茶水提液中的茶多酚和嘌呤生物碱进行了定性分析,检测到3种嘌呤生物碱、7种儿茶素类化合物和2种非儿茶素类茶多酚(没食子酰奎宁酸酯和咖啡酰奎宁酸酯)。同时与传统绿茶在儿茶素类化合物的组成和含量上进行了比较,结果显示,苦茶中总儿茶素含量(13.82%)远高于传统绿茶(7.37%),但各儿茶素类化合物的相对组成比在两种茶中极其相近,均以酯型儿茶素为主。     

我国代表性茶树种质嘌呤生物碱的鉴定

从国家种质杭州茶树圃选取了403份有代表性的茶树资源,采用HPLC对嘌呤生物碱进行了2年、春秋两季的重复鉴定。结果表明,年度和季节间咖啡碱含量总体稳定,但可可碱含量春季变化显著。93%以上资源的咖啡碱含量为25.0~45.0 mg/g。茶的3个变种间,咖啡碱含量存在显著差异,且阿萨姆茶秋季较春季咖啡碱含量明显增加。来源于不同地区的资源咖啡碱含量存在显著差异,其中云南和广东的资源变异系数和多样性指数最大。从403份资源中筛选出3份高咖啡碱、1份高苦茶碱(低咖啡碱)和2份高可可碱(低咖啡碱)等6份特异资源。     

福建云霄地方茶树品种资源生化成分特征分析与评价北大核心CSCD

以福建省云霄县小帽山、梁山和南乌山3个区域共23份地方茶树品种资源为试材,采用高效液相色谱(HPLC)法和超高效液相色谱-质谱联用(UPLC-MS/MS)法测定其儿茶素、嘌呤生物碱及氨基酸组分含量,并进行描述统计分析、差异分析和聚类分析,以筛选生化成分含量特异的茶树品种资源。结果表明:(1)23份茶树品种资源的儿茶素总量变化范围为73.54~260.31 mg·g^(-1),平均值为160.48 mg·g^(-1);表没食子儿茶素-3-O-甲基-没食子酸酯(EGCG3″Me)在所有资源中均检出,含量最高的为小帽山3号(X03),高达33.65 mg·g^(-1)。(2)23份茶树品种资源的嘌呤生物碱总量变化范围为15.28~70.42 mg·g^(-1),平均值为40.95 mg·g^(-1);苦茶碱(TC)在梁山地区的茶树品种资源(LS01-LS07)均检出,其中梁山6号(L06)和梁山7号(L07)的苦茶碱含量高于其咖啡碱含量。(3)23份茶树品种资源的氨基酸总量变化范围为6.40~47.57 mg·g^(-1),平均值为20.83 mg·g^(-1);氨基酸构成丰富,共检测出20种氨基酸物质。(4)差异分析和聚类分析结果显示,云霄县3个区域茶树资源的生化成分具有明显地域特征。其中梁山区域茶树资源富含苦茶碱(TC),小帽山茶树资源的表没食子儿茶素没食子酸酯(EGCG)和表没食子儿茶素-3-O-甲基-没食子酸酯(EGCG3″Me)含量较高,南乌山茶树资源的丙氨酸(Ala)、谷氨酸(Glu)、谷氨酰胺(Gln)含量略高于其他两地。研究发现,云霄地方茶树品种资源的儿茶素、嘌呤生物碱及氨基酸含量差异大,具有丰富的遗传多样性,区域特征明显,筛选出高儿茶素、高EGCG3″Me、高苦茶碱、高茶氨酸等18份优特茶树品种资源,为云霄地方茶树品种资源的系统开发利用奠定了基础。     

湖南茶叶植物资源的评价

对城步峒茶、江华苦茶、汝城白毛茶和云台山种等湖南茶叶植物资源的主要化学成分、光合特性和生产性状进行了研究。结果表明,茶多酚与儿茶素含量从高到低依次为汝城白毛茶、江华苦茶、城步峒茶、云台山种;各资源的游离氨基酸、茶氨酸和咖啡碱含量均为正常水平;汝城白毛茶属高茶多酚资源,它所含生物碱的组成方式与毛叶茶龙门模式种不同,虽可可碱和茶叶碱含量比茶种高,但仍以咖啡碱为主。在阴天阴凉条件下的净光合速率为汝城白毛茶＞城步峒茶＞江华苦茶＞云台山种,净光合速率与光量子通量、叶面温度呈极显著正相关,与气孔阻力呈极显著负相关,相关系数分别为０９２７８、０９１１５和－０８９３７。在晴天高温度强光条件下,净光合速率为云台山种＞城步峒茶＞江华苦茶＞汝城白毛花,净光合速率与光量子通量、叶面温度和气孔阻力都呈极显著负相关,相关系数分别为－０９１６５、－０９３２８、－０９０３１。在主要生产性状中,汝城白毛茶能安全通过－６℃的低温,在高茶多酚资源中,抗寒性突出,是选育红茶良种的一个非常有益的关键性状。     

冠突散囊菌对茶叶品质成分的影响研究

为揭示黑茶"发花"过程中冠突散囊菌对茶叶中主要品质成分的影响,以黑毛茶为原料,比较了"发花"前后各品质成分的差异。结果显示:"发花"过程中多酚类物质减少16.75%,黄酮类物质减少5.65%,水溶性蛋白减少22.77%,可溶性糖减少10.73%,水浸出物变化不明显。采用HPLC方法对"发花"前后黑毛茶中的氨基酸、生物碱、儿茶素、有机酸类成分的组成及含量进行比较:"发花"过程中氨基酸总量减少达88.62%,其中茶氨酸、谷氨酸、天冬氨酸、酪氨酸的下降最为剧烈;生物碱"发花"后呈上升的趋势,咖啡碱的含量提高8.55%,可可碱提高11.76%;儿茶素类成分总量下降,其中没食子酸和简单儿茶素"发花"后含量升高,其他酯型儿茶素降低;主要的有机酸类成分总含量下降,苹果酸下降迅速,琥珀酸的含量上升到发酵前的8.42倍,研究结果为科学阐述"发花"对黑茶的品质形成机理及其作用提供参考。     

汉中茶叶氨基酸含量测定及营养价值评价分析

为了解汉中茶区不同品种茶叶的营养成分,采用氨基酸自动分析仪法对南郑县、镇巴县目前种植的五种茶树品种中的氨基酸含量进行测定。结果表明,共检测出31种氨基酸,总含量(以干质量计)分别为中茶102 60.43 mg·g~(-1)、中茶108 66.14mg·g~(-1)、名山131 51.17mg·g~(-1)、乌牛早66.15mg·g~(-1)、南郑县紫阳群体种27.92mg·g~(-1)、镇巴县紫阳群体种33.45mg·g~(-1);必需氨基酸共7种,乌牛早中必需氨基酸含量最高,为2.83 mg·g~(-1);中茶108中茶氨酸含量最高,达53.73mg·g-1,占总含量93.6%;比较不同品种茶叶的氨基酸比值系数分(SRC)发现,中茶108、中茶102的SRC值最高,达68.504和62.663,营养价值高且均衡。综合比较,新引进品种的营养价值优于群体种。     

古蔺牛皮茶树种质资源性状初步研究

为开展四川重要茶树种质资源古蔺牛皮茶种质资源的收集、保存与评价工作,在古蔺牛皮茶树资源中选取了具代表性的8种不同类型茶树(Ⅰ~Ⅷ类)作为研究对象,并对其植物学特征、生物学特性及主要生化成分进行了观测。结果表明:供试茶树在形态特征、遗传和品质性状等方面,表现出较丰富的多样性。其种群多为灌木,树姿半开张状;芽叶绿色,茸毛中等,叶为椭圆形,叶尖渐尖;花多为中花型,花柱3~4裂;果实多为球形和肾形,种子多为球形,主要表现出栽培型茶树性状。古蔺牛皮茶春梢的生化成分含量较丰富,其茶多酚含量为(19.71±0.39)%~(30.16±0.22)%,游离氨基酸总量为(2.20±0.11)%~(4.88±0.12)%,咖啡碱含量为(3.45±0.17)%~(4.41±0.09)%。结合主要生化成分含量、酚/氨值和儿茶素组分等可推论,Ⅴ、Ⅵ类适制红茶,其他类型则适制绿茶。综合供试茶树的形态和生化成分含量特征,初步鉴定供试的牛皮茶树分属茶组植物分类系统中的秃房茶和茶,Ⅴ和Ⅵ类茶树较为原始,其他类型则进化程度较高。供试茶树中存在具育种价值的资源,其中Ⅴ类和Ⅵ类可作为高儿茶素含量的育种材料,Ⅱ类可作为选育优质绿茶品种的育种材料。     

不同甜叶菊品种叶中绿原酸类成分的比较研究

该文以14个扦插培育的甜叶菊品种叶为材料,从8种不同型号的树脂中筛选出一种合适的大孔吸附树脂对甜叶菊叶中绿原酸类成分进行纯化前处理,采用HPLC法对不同甜叶菊品种叶中所含绿原酸类成分进行比较分析。结果表明:(1)在8种不同型号的树脂中,XAD~(-1)6对甜叶菊叶中绿原酸类成分吸附-解析性能最佳。(2)经优化,上样液浓度1.20 mg·mL~(-1)、样品溶液pH 3、解析液乙醇体积分数70%时XAD~(-1)6树脂对甜叶菊叶中绿原酸类成分具有较好的纯化效果。(3) HPLC检测分析表明,在14个品种中共检测出新绿原酸、绿原酸、隐绿原酸、异绿原酸B、异绿原酸A、异绿原酸C六种绿原酸类成分,其中主要成分均为异绿原酸A、绿原酸、异绿原酸C,而在品种3、5、13、14中没有检测出异绿原酸B。(4) 14个品种中6个绿原酸类成分的含量分别为异绿原酸A 20.55~54.3 mg·g~(-1)、绿原酸17.96~32.93 mg·g~(-1)、异绿原酸C 4.15~19.49 mg·g~(-1)、新原酸0.61~4.61 mg·g~(-1)、隐绿原酸0.52~3.11 mg·g~(-1)、异绿原酸B 0.0~3.17 mg·g~(-1),6种绿原酸类成分总量为43.9~97.8 mg·g~(-1)。可见,不同品种甜叶菊叶中绿原酸类成分含量有明显差异,富含绿原酸类成分的甜叶菊品种可用于开发获取绿原酸类物质。     

普洱茶后发酵中咖啡碱变化研究进展(综述)

普洱茶（熟茶）的后发酵加工工艺,是形成其独特品质特征的关键工序。咖啡碱是一种甲基黄嘌呤,是茶叶中含量比较丰富的生化成分之一,也是茶叶主要呈味物质和生理活性成分,具有促进兴奋、强心、解毒、利尿、助消化等功效。咖啡碱在普洱茶后发酵过程中呈增加趋势。文章对普洱茶后发酵过程中咖啡碱变化的相关研究进行系统综述,为普洱茶咖啡碱理论研究提供科学依据。     

光源或培养基成分对金花茶愈伤组织中DFR、LAR与PPO基因表达及总儿茶素含量的影响

该研究以富含儿茶素的金花茶愈伤组织为材料,对不同光源、激素、碳源及苯丙氨酸处理30 d的愈伤组织中DFR表达量、LAR表达量、PPO表达量与总儿茶素含量的变化情况及四者两两之间的相关性进行了分析.结果表明:这4个检测项目均对以上处理有显著的响应;在以上各因素处理下,DFR与LAR的表达模式十分相似,其相关系数处在0.710~0.889之间;在不同碳源处理下,PPO表达量与总儿茶素含量的变化呈显著负相关关系,其相关系数为-0.696;在不同苯丙氨酸添加量处理下,DFR与LAR表达量变化均与总儿茶素含量变化呈显著正相关关系,其相关系数分别为0.786和0.564;适宜儿茶素离体生产的金花茶愈伤组织增殖配方为附加4 mg·L-16-BA、0.6 mg·L-12,4-D、30 g·L-1蔗糖与0.6608 g·L-1苯丙氨酸的MS固体培养基,其总儿茶素含量可达40.11 mg·g-1 DW.以上研究表明,与茶树相似,在金花茶中DFR与LAR在儿茶素代谢过程中密切相关;PPO表达量升高导致金花茶儿茶素损失;添加适宜浓度的苯丙氨酸作为前体物质是提高愈伤组织中总儿茶素含量的有效措施.     

不同亚硒酸钠浓度对党参生长、生理特性和品质的影响

为综合了解党参的施硒效应，该研究基于水培试验探究不同亚硒酸钠浓度处理条件下党参幼苗的硒积累、生长、生理和品质的变化规律。结果表明：(1)适宜硒浓度(0.2 mg·L^-1)可以促进党参的叶片面积、株高、生物量的增长，而高硒浓度(10 mg·L^-1)则抑制党参生长。(2)增加亚硒酸钠浓度和硒暴露时间均可提高党参幼苗在根和叶中的硒含量，不同器官硒积累表现为根>叶>茎。(3)适宜硒浓度(0.2 mg·L^-1)处理可提高光合色素含量和根系活力，并减少丙二醛、脯氨酸和过氧化氢的积累，而高硒浓度(10 mg·L^-1)则与之相反。(4)适宜硒浓度(0.2 mg·L^-1)有利于党参炔苷、多糖、可溶性蛋白的积累，而高硒浓度(10 mg·L^-1)可以对多糖和可溶性蛋白的积累产生不利影响。综上认为，亚硒酸钠对党参具有双重效应，施加适量浓度对党参的生长、生理和品质有益，并以0.2 mg·L^-1硒浓度处理的效果最佳。该研究结果有助于了解亚硒酸钠浓度对...     

Biosynthesis and metabolism of purine alkaloids in leaves of cocoa tea (Camellia ptilophylla)

The biosynthesis and metabolism of purine alkaloids in leaves ofCamellia ptilophylla (cocoa tea), a new tea resource in China, have been investigated. The major purine alkaloid was theobromine, with theophylline also being present as a minor component. Caffeine was not accumulated in detectable quantities. Theobromine was synthesized from [8-¹⁴C] adenine and the rate of its biosynthesis in the segments from young and mature leaves from flush shoots was approximately 10 times higher than that from aged leaves from 1-year old shoots. Neither cellfree extracts nor segments fromC. ptilophylla leaves could convert theobromine to caffeine. A large quantity of [2-¹⁴C] xanthine taken up by the leaf segments was degraded to¹⁴CO₂ via the conventional purine catabolic pathway that includes allantoin as an intermediate. However, small amounts of [2-¹⁴C] xanthine were also converted to theobromine. Considerable amounts of [8-¹⁴C] caffeine exogenously supplied to the leaf segments ofC. ptilophylla was changed to theobromine. These results indicate that leaves ofC. ptilophylla exhibit unusual purine alkaloid metabolism as i) they have the capacity to synthesize theobromine from adenine nucleotides, but they lack adequate methyltransferase activity to convert of theobromine to caffeine in detectable quantities, ii) the leaves have a capacity to convert xanthine to theobromine, probably via 3-methylxanthine.     

氧化石墨烯对多年生黑麦草逆境生理及光合特征的影响

为探讨不同浓度氧化石墨烯（GO）对多年生黑麦草生长、生理及光合特征的影响,该文采用盆栽试验,在土壤中添加0、10、20、30、40、50 mg·g^-1 GO进行多年生黑麦草培养,并测定植物生长指标、光合色素含量、保护酶活性、丙二醛（MDA）含量、叶片质膜透性、可溶性蛋白含量和光合参数。结果表明：（1）10、20 mg·g^-1 GO处理对多年生黑麦草生长无显著影响;30～50 mg·g^-1 GO处理对多年生黑麦草生长具有抑制作用,在50 mg·g^-1 GO浓度下多年生黑麦草株高和生物量均最小,较对照分别降低了16.8%和27.1%。（2）当GO浓度达到30 mg·g^-1时,总叶绿素和类胡萝卜素的含量显著降低,在50 mg·g^-1 GO处理时达到最低。（3）高浓度的GO处理(40、50 mg·g^-1)虽降低了多年生黑麦草的叶片净光合速率（P_n）、气孔导度（G_s）和蒸腾速率（T_r     

金花茶组植物花色与细胞内重要环境因子的关系

为研究金花茶组植物花色与细胞内重要环境因子的关系,该研究以花色不同的8个金花茶组物种的9个居群为材料,测定了其花瓣的颜色、总黄酮含量、含水量、细胞pH、7种金属离子浓度。结果表明:所测金花茶组植物的花色平均明度L~*为80.82、色相a~*为-2.88、色相b~*为53.97、彩度C~*为54.10、色相角h为93.19°,故金花茶花色为明度较亮的黄色,其中色相b~*为描述黄色的主要指标,据此可将所测植物分为金黄、黄、浅黄3类。花瓣总黄酮含量为20.17%,花瓣含水量为88.14%,物种间均达到差异显著,且均与花色呈弱相关,对黄色呈现影响较小。花瓣细胞偏弱酸性,pH平均值为6.19,不同物种间差异显著,细胞pH与花色呈显著正相关,即中偏弱酸性细胞环境有利于金花茶花瓣黄色的呈现。金属离子浓度中,K~+含量最高(12.61 mg·g~(-1)),其他依次为Ca2+(3.91 mg·g~(-1))、Mg~(2+)(1.28 mg·g~(-1))、Al~(3+)(0.98 mg·g~(-1))、Na~+(0.17mg·g~(-1))、Fe~(3+)(0.07 mg·g~(-1)),Cu~(2+)含量最低(0.003 8 mg·g~(-1)),7种金属离子在所测植物间均存在显著差异,其中Al~(3+)、Fe~(3+)和Ca~(2+)对金花茶黄色花的形成具有不同程度的干扰作用,随着这3种金属离子浓度升高,黄度降低,花色变淡。因此,较低浓度的Al~(3+)、Fe~(3+)、Ca~(2+)可能更有利于金花茶黄色花的呈现。     

铊和镉胁迫对芦竹生长及光合特征的影响

芦竹(Arundo donax)对多种重金属都有较好的耐受性,是植物修复技术较理想的选择,而关于芦竹对Cd和Tl胁迫生理反应的相关研究却较少,为了有效治理Cd和Tl的污染,本研究以芦竹为材料,通过添加不同浓度重金属Tl(4,10和20 mg·kg~(-1))、Cd(50,100和200 mg·kg~(-1))进行芦竹盆栽试验,测定芦竹的株高、分蘖数、叶绿素含量、光合生理指标以及Tl和Cd在芦竹中的累积量,探讨芦竹对Tl和Cd胁迫的响应机制。结果表明:Tl(4~20 mg·kg~(-1))和Cd(50~200 mg·kg~(-1))对芦竹株高、分蘖数以及叶绿素含量均无显著影响(P0.05);芦竹体内Tl和Cd含量随着Tl和Cd浓度的升高呈上升趋势,芦竹体内Tl含量的分布规律为根茎叶,Cd含量的分布规律:Cd浓度50 mg·kg~(-1)时为茎叶根,Cd浓度100和200 mg·kg~(-1)时为根茎叶,表明Tl和Cd主要分布在根部,芦竹对Tl、Cd有一定的富集能力。Cd和Tl处理均显著降低芦竹叶片的胞间CO2浓度,在Tl浓度为10 mg·kg~(-1)时,净光合速率、气孔导度和蒸腾速率得到显著提高,当Cd浓度为50 mg·kg~(-1)时,净光合速率、气孔导度和蒸腾速率得到显著提高。这表明芦竹对重金属Cd和Tl有较强的耐受性,可为Cd和Tl污染土壤的治理和修复提供参考。     

Metabolism of purine bases, nucleosides and alkaloids in theobromine-forming Theobroma cacao leaves

We examined the purine alkaloid content and purine metabolism in cacao (Theobroma cacao L.) plant leaves at various ages: young small leaves (stage I), developing intermediate size leaves (stage II), fully developed leaves (stage III) from flush shoots, and aged leaves (stage IV) from 1-year-old shoots. The major purine alkaloid in stage I leaves was theobromine (4.5 μmol g^–1 fresh weight), followed by caffeine (0.75 μmol g^–1 fresh weight). More than 75% of purine alkaloids disappeared with subsequent leaf development (stages II–IV). In stage I leaves, ¹⁴C-labelled adenine, adenosine, guanine, guanosine, hypoxanthine and inosine were converted to salvage products (nucleotides and nucleic acids), to degradation products (ureides and CO₂) and to purine alkaloids (3- and 7-methylxanthine, 7-methylxanthosine and theobromine). In contrast, ¹⁴C-labelled xanthine and xanthosine were not used for nucleotide synthesis. They were completely degraded, but nearly 20% of [8-¹⁴C]Xanthosine was converted in stage I leaves to purine alkaloids. These observations are consistent with the following biosynthetic pathways for theobromine: (a) AMP → IMP → 5′-xanthosine monophosphate → xanthosine → 7-methylxanthosine → 7-methylxanthine → theobromine; (b) GMP → guanosine → xanthosine → 7-methylxanthosine → 7-methylxanthine → theobromine; (c) xanthine → 3-methylxanthine → theobromine. Although no caffeine biosynthesis from ¹⁴C-labelled purine bases and nucleosides was observed during 18 h incubations, exogenously supplied [8-¹⁴C]Theobromine was converted to caffeine in young leaves. Conversion of theobromine to caffeine may, therefore, be slow in cacao leaves. No purine alkaloid synthesis was observed in the subsequent growth stages (stages II–IV). Significant degradation of purine alkaloids was found in leaves of stages II and III, in which [8-¹⁴C]Theobromine was degraded to CO₂ via 3-methylxanthine, xanthine and allantoic acid. [8-¹⁴C]Caffeine was catabolised to CO₂ via theophylline (1,3-dimethylxanthine) or theobromine.     

Biosynthesis of Caffeine in Flower Buds of Camellia sinensis

The biosynthesis of purine alkaloids in flower buds of tea plantswas investigated. More than 25% of total radioactivity of [8-¹⁴C]adeninetaken up by stamens isolated from tea flower buds was foundto have been incorporated into purine alkaloids, namely, theobromineand caffeine, 24 h after administration of the labelled compound.Pulse-chase experiments indicated that [8-¹⁴C]adenine takenup by the stamens was converted to adenine nucleotides and subsequentlyincorporated into theobromine and caffeine. Since 5 µMcoformycin, an inhibitor of AMP deaminase, inhibited the incorporationof radioactivity into the purine alkaloids, synthesis of caffeinefrom adenine nucleotides seems to be initiated by the reactionof AMP deaminase. Although most of the radioactivity from [8-¹⁴C]inosinewas recovered as CO₂ and ureides, considerable amounts of radioactivitywere recovered as purine alkaloids. The incorporation of radioactivityfrom [8-¹⁴C]inosine into the purine alkaloids was not affectedby coformycin. The five enzymes involved in synthesis of 5-phosphoribosyl-1-pyrophosphatefrom glucose were present in the stamens and petals of tea flowerbuds. From present and previous results, the pathway for thebiosynthesis of caffeine from adenine nucleotides in flowerbuds of tea is discussed.Copyright 1993, 1999 Academic Press Camellia sinensis, tea, stamen, flower, biosynthesis, purine alkaloids, caffeine, theobromine, adenine nucleotides, nucleotide biosynthesis     

Purine Alkaloids of the Fruits of Camellia sinensis L. and Coffea arabica L. during Fruit Development

The amounts of two purine alkaloids, caffeine and theobromine,in the fruit of tea (Camellia sinensis L.) increased markedlyduring the growing season until the fruit was full-ripened anddried. In the dry fruit, the pericarp contained the most alkaloids,but there were also considerable amounts in the seed coat and,to a lesser extent, the fruit stalk and the seed. The shed seedsalso contained significant amounts of the alkaloids, especiallyin the seed coats. In contrast with the dry fruit of tea, seedsand pericarp of coffee (Coffea arabica L.) fruit contained aconsiderable amount of caffeine and a small amount of theobromide.A small amount of theophylline was also present in the pericarpof the ripened fruit. Relationships between growth and purinealkaloid content in tea and coffee fruits and their roles duringseed formation are discussed. Camellia sinensis L., tea, Coffea arabica L., coffee, purine alkaloids, fruit development, seed, seed coat, caffeine, theobromine, theophylline     

Substrate specificity of N-methyltransferase involved in purine alkaloids synthesis is dependent upon one amino acid residue of the enzyme

Caffeine (1,3,7-trimethylxanthine) and theobromine (3,7-dimethylxanthine) are the major purine alkaloids in plants. To investigate the diversity of N-methyltransferases involved in purine alkaloid biosynthesis, we isolated the genes homologous for caffeine synthase from theobromine-accumulating plants. The predicted amino acid sequences of N-methyltransferases in theobromine-accumulating species in Camellia were more than 80% identical to caffeine synthase in C. sinensis. However, there was a little homology among the N-methyltransferases between Camellia and Theobroma. The recombinant enzymes derived from theobromine-accumulating plants had only 3-N-methyltransferase activity. The accumulation of purine alkaloids was, therefore, dependent on the substrate specificity of N-methyltransferase determined by one amino acid residue in the central part of the protein.