Genetical and biochemical evidence that the hydroxylation pattern of the anthocyanin B-ring in Silene dioica is determined at the p-coumaroyl-coenzyme a stage

In petals of Silene dioica, gene P controls the 3′-hydroxylation of the anthocyanin B-ring and the hydroxylation pattern of the hydroxycinnamoyl acyl group bound to the 4″'-hydroxyl group of rhamnose of anthocyanidin 3-rhamnosyl(1→6)glucoside-5-glucoside. In this paper, experiments are presented which show that gene P is involved in the hydroxylation of p-coumaroyl-CoA to caffeoyl-CoA, which is then used both as a precursor in anthocyanin biosynthesis and as a substrate for the final acylation.     

Study on the interaction between pelargonidin‐3‐O‐glucoside and bovine serum albumin using spectroscopic,transmission electron microscopy and molecular modeling techniques

The aim of this study is to evaluate the binding behavior between pelargonidin‐3‐O‐glucoside (P3G) and bovine serum albumin (BSA) using multi‐spectroscopic, transmission electron microscopy (TEM) and molecular docking methods under physiological conditions. Fluorescence spectroscopy and time‐resolved fluorescence showed that the fluorescence of BSA could be quenched remarkably by P3G via a static quenching mechanism, and there is a single class of binding site on BSA. In addition, the thermodynamic functions ΔH and ΔS were –21.69 kJ/mol and 24.46 J/mol/K, indicating that an electrostatic interaction was a main acting force. The distance between BSA and P3G was 2.74 nm according to Förster's theory, illustrating that energy transfer occurred. In addition, the secondary structure of BSA changed with a decrease in the α‐helix content from 66.2% to 64.0% as seen using synchronous fluorescence, UV/vis, circular dichroism and Fourier transform infrared spectroscopies, whereas TEM images showed that P3G led to BSA aggregation and fibrillation. Furthermore, site marker competitive experiments and molecular docking indicated that P3G could bind with subdomain IIA of BSA. The calculated results of the equilibrium fraction showed that the concentration of free P3G in plasma was high enough to be stored and transported from the circulatory system to its target sites to provide therapeutic effects. Copyright © 2015 John Wiley & Sons, Ltd.     

水杨酸酰化对胭脂萝卜天竺葵素稳定性和抗氧化活性的影响

为探究水杨酸作为酰化剂对胭脂萝卜天竺葵素的稳定性和抗氧化活性的影响,以保留率为指标,分析光、温度、金属离子、pH及氧化剂对酰化天竺葵素稳定性的影响,探究酰化天竺葵素对羟自由基、DPPH自由基和ABTS自由基的清除能力。结果表明:酰化天竺葵素对光、温度、Al3+、pH的稳定性显著提高,对Fe2+、Mg2+和Zn2+以及氧化剂H2O2的稳定性无显著差影响。酰化天竺葵素对羟自由基、DPPH自由基和ABTS自由基的清除能力与未酰化天竺葵素无显著差异。以上结果表明采用水杨酸酰化胭脂萝卜天竺葵素不影响其抗氧化活性,还能提高其对光照、温度、pH及铝离子的稳定性。     

Properties and genetic control of udp-l-rhamnose: anthocyanidin 3-O-glucoside, 6″-O-rhamnosyl-transferase from petals of red campion,Silene dioica

In petals of Silene dioica plants the presence of a glycosyltransferase has been demonstrated, which catalyses the transfer of the rhamnosyl moiety of UDP-l-rhamnose to the glucose of cyanidin 3-O-glucoside. This enzyme can also use pelargonidin 3-O-glucoside as a substrate. The enzyme activity is controlled by a single dominant gene N; no rhamnosyltransferase activity is found in petals of n/n plants. The rhamnosyltransferase exhibits an optimum of pH 8.1 and is stimulated by the divalent metal ions Mg, Mn and Co. The biosynthetic pathway for the synthesis of cyanidin 3-rhamnosylglucoside-5-glucoside in petals of S. dioica is discussed.     

Apigeninidin as a leucoderivative in Ephedra frustillata

Aerial parts of Ephedra frustillata are shown to contain leucoderivatives based on apigeninidin and pelargonidin. This is the first report of leuco     

细叶小檗果色素成分研究

细叶小檗(Berberis poiretii schneid)之红色浆果,经压榨得鲜果汁。采用醋酸铅沉淀,正丁醇提取的纯化方法,得到纯化色素。此色素在三种溶剂系统中纸层析,均显示两条不同红色谱带。酸水解后,甙元部分与标准品对照,在三种溶剂系统中进行纸层析,证明含有下面两个花青甙元:(1)天竺葵甙元(pelargonidin)、(2)矢车菊甙元(cyanidin)。纸层析制备后,在0.1％盐酸-乙醇中测定两个花青甙元的吸收光谱,最大吸收峰分别在532mm和547mm。配糖的测定用甲酸水解,与标准糖对照纸层析和薄层层析,证明配糖为葡萄糖和阿拉伯糖。色素经纸层析制备成两条谱带后,分别用高效薄层法直接水解,与标准糖对照层析,证明色素1配糖为葡萄糖,色素2配糖为葡萄糖和阿拉伯糖。     

Redirection of anthocyanin synthesis in Osteospermum hybrida by a two-enzyme manipulation strategy

Modern biotechnology has developed powerful tools for genetic engineering and flower colours are an excellent object to study possibilities and limitations of engineering strategies. Osteospermum hybrida became a popular ornamental plant within the last 20 years. Many cultivars display rose to lilac flower colours mainly based on delphinidin-derived anthocyanins. The predominant synthesis of delphinidin derivatives is referred to a strong endogenous flavonoid 3',5'-hydroxylase (F3'5'H) activity. Furthermore, since dihydroflavonol 4-reductase (DFR) of Osteospermum does not convert dihydrokaempferol (DHK) to leucopelargonidin, synthesis of pelargonidin-based anthocyanins is naturally not realised. In order to redirect anthocyanin biosynthesis in Osteospermum towards pelargonidin derivatives, we introduced cDNAs coding for DFRs which efficiently convert DHK to LPg. But neither the expression of Gerbera hybrida DFR nor of Fragaria x ananassa DFR - the latter is characterised by an unusual high substrate preference for DHK - altered anthocyanin composition in flowers of transgenic plants. However, chemical inhibition of F3'5'H activity in ray florets of dfr transgenic plants resulted in the accumulation of pelargonidin derivatives. Accordingly, retransformation of a transgenic plant expressing Gerbera DFR with a construct for RNAi-mediated suppression of F3'5'H activity resulted in double transgenic plants accumulating predominantly pelargonidin derivatives in flowers.     

Alteration of a single amino acid changes the substrate specificity of dihydroflavonol 4-reductase

Many plant species exhibit a reduced range of flower colors due to the lack of an essential gene or to the substrate specificity of a biosynthetic enzyme. Petunia does not produce orange flowers because dihydroflavonol 4-reductase (DFR) from this species, an enzyme involved in anthocyanin biosynthesis, inefficiently reduces dihydrokaempferol, the precursor to orange pelargonidin-type anthocyanins. The substrate specificity of DFR, however, has not been investigated at the molecular level. By analyzing chimeric DFRs of Petunia and Gerbera, we identified a region that determines the substrate specificity of DFR. Furthermore, by changing a single amino acid in this presumed substrate-binding region, we developed a DFR enzyme that preferentially reduces dihydrokaempferol. Our results imply that the substrate specificity of DFR can be altered by minor changes in DFR.     

Pleiotropic effect of a pelargonidin-hydroxylation gene in Silene dioica?

In petals of Silene dioica a gene P has been identified, which controls the 3′-hydroxylation of the B-ring of pelargonidin to cyanidin. Another gene Ac controls the acylation of the terminal sugar at the 3-position of anthocyanin 3-rhamnosylglucoside-5-glucosides. In p/p plants the bound acyl group is p-coumaric acid; in P/P plants, however, it is caffeic acid. Gene P seems to exert a pleiotropic effect: it not only controls the hydroxylation of the B-ring of pelargonidin but also that of the acyl group.