Anthocyanins from red flowers of Camellia cultivar 'Dalicha'

Five anthocyanins, cyanidin 3-O-(2-O-β-xylopyranosyl-6-O-(Z)-p-coumaroyl)-β-galactopyranoside (2), cyanidin 3-O-(2-O-β-xylopyranosyl-6-O-(E)-p-coumaroyl)-β-galactopyranoside (3), cyanidin 3-O-(2-O-β-xylopyranosyl-6-O-(E)-caffeoyl)-β-galactopyranoside (4), cyanidin 3-O-(2-O-β-xylopyranosyl-6-O-acetyl)-β-galactopyranoside (5), and cyanidin 3-O-(2-O-β-xylopyranosyl-6-O-acetyl)-β-glucopyranoside (6), together with the known cyanidin 3-O-(2-O-β-xylopyranosyl)-β-galactopyranoside (1), were isolated from red flowers of Camellia cultivar ‘Dalicha’ (Camellia reticulata) by chromatography using open columns. Their structures were subsequently determined on the basis of spectroscopic analyses, i.e., ¹H NMR, ¹³C NMR, HMQC, HMBC, HR ESI-MS and UV-vis.     

The Arabidopsis UDP‐glycosyltransferases UGT79B2 and UGT79B3, contribute to cold,salt and drought stress tolerance via modulating anthocyanin accumulation

The plant family 1 UDP‐glycosyltransferases (UGTs) are the biggest GT family in plants, which are responsible for transferring sugar moieties onto a variety of small molecules, and control many metabolic processes; however, their physiological significance in planta is largely unknown. Here, we revealed that two Arabidopsis glycosyltransferase genes, UGT79B2 and UGT79B3, could be strongly induced by various abiotic stresses, including cold, salt and drought stresses. Overexpression of UGT79B2/B3 significantly enhanced plant tolerance to low temperatures as well as drought and salt stresses, whereas the ugt79b2/b3 double mutants generated by RNAi (RNA interference) and CRISPR‐Cas9 strategies were more susceptible to adverse conditions. Interestingly, the expression of UGT79B2 and UGT79B3 is directly controlled by CBF1 (CRT/DRE‐binding factor 1, also named DREB1B) in response to low temperatures. Furthermore, we identified the enzyme activities of UGT79B2/B3 in adding UDP‐rhamnose to cyanidin and cyanidin 3‐O‐glucoside. Ectopic expression of UGT79B2/B3 significantly increased the anthocyanin accumulation, and enhanced the antioxidant activity in coping with abiotic stresses, whereas the ugt79b2/b3 double mutants showed reduced anthocyanin levels. When overexpressing UGT79B2/B3 in tt18 (transparent testa 18), a mutant that cannot synthesize anthocyanins, both genes fail to improve plant adaptation to stress. Taken together, we demonstrate that UGT79B2 and UGT79B3, identified as anthocyanin rhamnosyltransferases, are regulated by CBF1 and confer abiotic stress tolerance via modulating anthocyanin accumulation.     

Functional characterization of UDP‐rhamnose‐dependent rhamnosyltransferase involved in anthocyanin modification,a key enzyme determining blue coloration in Lobelia erinus

Because structural modifications of flavonoids are closely related to their properties, such as stability, solubility, flavor and coloration, characterizing the enzymes that catalyze the modification reactions can be useful for engineering agriculturally beneficial traits of flavonoids. In this work, we examined the enzymes involved in the modification pathway of highly glycosylated and acylated anthocyanins that accumulate in Lobelia erinus. Cultivar Aqua Blue (AB) of L. erinus is blue‐flowered and accumulates delphinidin 3‐O‐p‐coumaroylrutinoside‐5‐O‐malonylglucoside‐3′5′‐O‐dihydroxycinnamoylglucoside (lobelinins) in its petals. Cultivar Aqua Lavender (AL) is mauve‐flowered, and LC‐MS analyses showed that AL accumulated delphinidin 3‐O‐glucoside (Dp3G), which was not further modified toward lobelinins. A crude protein assay showed that modification processes of lobelinin were carried out in a specific order, and there was no difference between AB and AL in modification reactions after rhamnosylation of Dp3G, indicating that the lack of highly modified anthocyanins in AL resulted from a single mutation of rhamnosyltransferase catalyzing the rhamnosylation of Dp3G. We cloned rhamnosyltransferase genes (RTs) from AB and confirmed their UDP‐rhamnose‐dependent rhamnosyltransferase activities on Dp3G using recombinant proteins. In contrast, the RT gene in AL had a 5‐bp nucleotide deletion, resulting in a truncated polypeptide without the plant secondary product glycosyltransferase box. In a complementation test, AL that was transformed with the RT gene from AB produced blue flowers. These results suggest that rhamnosylation is an essential process for lobelinin synthesis, and thus the expression of RT has a great impact on the flower color and is necessary for the blue color of Lobelia flowers.     

光照强度对成熟红颜草莓果实着色和花青素生物合成的影响及可能的分子机制

为了研究光照对红颜草莓（Fragaria×ananassa Duch.‘Benihoppe’）果实着色、花青素含量及花青素合成相关基因表达的影响,本文采用高效液相色谱法（HPLC）和实时荧光定量PCR技术测定了不同遮阴处理下（透光率100%、75%、25%）草莓果实花青素含量及色素相关基因的表达情况。结果显示,与100%透光率下的草莓果实相比,在75%和25%透光率下合成的花青素含量分别下降了41.58%和92.54%;和花青素合成相关基因的表达也都有不同程度的下降,其中二氢黄酮醇4-还原酶基因（FaDFR）、类黄酮-3'羟化酶基因（FaF3'H）和类黄酮3-O-糖基转移酶基因（FaUFGT）的表达与花青素含量相关性达到显著水平;此外,在遮光条件下转录因子FaMYB10、FaMYB1表达也明显下调。可见,光照是影响草莓果实着色的关键环境因素,遮光抑制色素相关功能基因和转录因子的表达,阻碍了果实中花青素的合成,最终导致果实着色差异。     

Antioxidant activities of red versus green leaves in Elatostema rugosum

Anthocyanin biosynthesis in leaves increases under stresses which also generate reactive oxygen species (ROS). In the present study the hypothesis that red leaves are better equipped to scavenge ROS than green leaves was tested. Antioxidants in leaf extracts from red and green morphs of Elatostema rugosum were identified, and activities quantified using enzymatic and α,α‐diphenyl‐β‐picrylhydrazyl (DPPH) assays and cyclic voltammetry. Red leaves from E. rugosum held greater amounts of superoxide dismutase, catalase, anthocyanins, and hydroxycinnamic acids, were significantly more effective at scavenging DPPH radicals, and produced higher voltammetric currents than green leaves. Anthocyanins contributed to the antioxidant pool more than all other constituent phenolics. Anthocyanin concentrations, and antioxidant activities declined with leaf age. Purified anthocyanin fractions displayed oxidative activities at both pH 7·0 and pH 5·5. Implications of the antioxidant potential of anthocyanin in its cytoplasmic and vacuolar locations are discussed.     

黑米中花青苷色素的测定方法研究

以 4种黑米为实验材料 ,用酸性乙醇作为提取溶剂 ,以色价值为色素含量的评价依据 ,研究了时间、温度、提取批次和脱脂对黑米中花青苷色素提取的影响。结果表明 :80℃ ,酸性乙醇 ,6 0min重复提取 2次 ,可实现 90 %以上的色素溶出。在最大吸收峰 5 35nm处测定提取液的ABS值 ,计算色价 ,作为黑米中花青苷色素的测定方法 ,可用于黑米品质分析     

不同溶剂和保存条件对尾叶悬钩子花色素苷提取及稳定性的影响

对尾叶悬钩子(Rubus caudifolius Wuzhi)鲜果中花色素苷的提取条件、主要化学组分及pH值、温度、没食子酸和Al^3 对其颜色及稳定性的影响进行了分析探讨。结果表明,尾叶悬钩子花色素苷的主要组分可能为矢车菊素-3-葡萄糖苷;pH值和温度影响该花色素苷的色泽及其稳定性,随着pH值和温度的增加,其分解加剧,且花色素苷的分解均遵循动力学一级反应规律;添加不同浓度的Al^3 ,色素溶液的吸光值有所升高,显示出有一定的增色效应,但Al^3 和没食子酸对贮藏期间花色素苷的稳定性及色泽均无明显效果。     

黑米皮花青苷色素测定方法的研究

以五种黑米皮为实验材料 ,采用优化方法 ,确定了黑米花青苷类色素测定实验条件。结果表明 :黑米皮脱脂后 ,80℃、酸性乙醇 ( 1 .5mol/LHCl-95 %乙醇 =1 5 /85 )、6 0min重复提取两次 ,可实现 95 %以上的色素溶出。提取液选取 1cm比色皿、与 5 35nm波长下测定ABS值 ,计算色价 (E 1%1cm ,λ=53 5nm　　　　 ) ,作为一种黑米花青苷类色素含量测定方法 ,可用于黑米品质分析