辣椒素的荧光分析方法研究

荧光分光光度法可用于辣椒及高纯度辣椒素样品中辣椒素的定量分析。在Ex为278 nm,Em为312 nm荧光条件下,辣椒素在0.58-5.8μg/mL浓度范围内其浓度C(μg/mL)与荧光强度I具有良好线性关系,回归方程c=1.0377×10-3I-0.3667,R=0.9994,精密度RSD=0.08%(n=5)。平均回收率95.39%。     

高效液相色谱法测定辣椒干中辣椒素的含量

本文建立了简便、快速的分离测定辣椒干中辣椒素含量的高效液相色谱法.HPC的条件Burospher-100 C18柱(I.D.250 mm×4.6 mm,5μm);流动相为甲醇-水(7030,V/V);流速为0.6 mL/min;检测波长为280 nm.在上述条件下,辣椒素在1.01～121.2 mg/L的范围内线性关系良好,线性相关系数γ=0.9994;实验结果表明,该方法的相对标准偏差在1.38%(n=6)以内,平均回收率为99.88%.     

羊角椒辣味物质成份分析

用紫外光谱法、红外光谱法和高效液相色谱法分析羊角椒中辣味物质纯度与组成,表明辣味物质由辣椒素、二氢辣椒素和降二氢辣椒素组成。     

The accumulation of phenylpropanoid and capsaicinoid compounds in cell cultures and whole fruit of the chilli pepper,Capsicum frutescens Mill

The accumulation of the phenylpropanoid precursors of capsaicin in suspended and immobilised cell cultures of C. frutescens has been studied and compared with accumulation in whole pepper fruit. The use of HPLC techniques has revealed that the phenolic precursors of capsaicin are present in chilli pepper cells at extremely low levels, irrespective of the source of tissue or the developmental state. Radioactive tracer studies have indicated that the majority of the phenolic derivatives of phenylalanine are ultimately bound to the insoluble fraction of the cells. Results from experiments where immobilised cell cultures were grown under conditions which enhance capsaicin yield would suggest that the diversion of compounds into this bound fraction has a considerable influence upon capsaicin biosynthesis in this system.     

Anthocyanin acyltransferases: specificities, mechanism, phylogenetics, and applications

Anthocyanins are responsible for the orange to blue coloration of flowers, fruits, and leaves. They are beneficial to human health and widely used as food colorants. Anthocyanin acyltransferases (AATs) are the plant enzymes that catalyze the regiospecific acyl transfer from acyl-CoA to the sugar moiety of anthocyanins. AATs are classified on the basis of their acyl-donor specificity into two categories; i.e. aliphatic and aromatic acyltransferases. However, the acyl-acceptor specificity of AAT differs greatly with the enzyme. Primary structural analyses of several AATs revealed that AATs form a subfamily within the versatile acyltransferase family and share highly conserved sequences such as motif 1 (-His-Xaa₃-Asp-) and motif 3 (-Asp-Phe-Gly-Trp-Gly-) with each other. It is proposed that AAT-catalyzed acyl transfer proceeds with a general acid/base mechanism, where the enzyme and both acyl donor and acyl acceptor form a ternary complex before catalysis can occur. The histidine and aspartic acid residues located at motifs 1 and 3, respectively, appear to play very important roles during the proposed general acid/base catalysis. AAT cDNAs have been expressed in heterologous systems, providing a basis for applications of AATs in biotechnology, such as flower color modification and food colorant production by metabolic engineering of anthocyanin biosynthesis in plants.     

In vitro capsaicin production by immobilized cells and placental tissues of Capsicum annuum L. grown in liquid medium

Capsaicin, from green pepper fruits is used in formulated foods and in pharmaceuticals. Cell cultures of Capsicum annuum L. were obtained from seedlings on Murashige and Skoog (MS) medium supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) and kinetin. In vitro-grown cells and placental tissues from fruits were immobilized in calcium alginate. Immobilized cells and placental tissues produced capsaicin which leached out into the medium. Immobilized placental tissue exhibited greater potentiality for capsaicin synthesis than immobilized cells. Production reached a level of 1345 μg capsaicin g⁻¹ of immobilized placenta on the 14th day of culture. Production of capsaicin, on replenished nutrient medium in immobilized placenta was 2400 μg on the 30th day. Ferulic acid fed to immobilized placenta at 2.5 mM level increased capsaicin production by 2-fold by the 5th day of the culture period. Of the elicitors used, curdlan was effective on capsaicin production in immobilized cells. Extracts of Aspergillius niger and Rhizopus oligosporus stimulated capsaicin production in immobilized placental tissues.     

植物次生代谢基因工程

植物次生代谢基因工程,是利用基因工程技术对植物次生代谢途径的遗传特性进行改造,进而改变植物次生代谢产物。植物次生代谢基因工程的出现是人类对次生代谢途径的深入了解和分子生物学向纵深发展的结果,同时它又促进了次生代谢分子生物学的发展。调控因子的应用和多基因的协同转化为植物次生代谢基因工程拓宽了思路。从次生代谢图谱、植物基因工程策略和植物转基因方法等方面对植物次生代谢的基因工程研究进展做一简要概述。     

Acyl-coenzyme A:cholesterol acyltransferase family

The enzymes of the acyl-coenzyme A:cholesterol acyltransferase (ACAT) family are responsible for the in vivo synthesis of neutral lipids.They are potential drug targets for the intervention of atherosclerosis,hyperlipidemia,obesity,type Ⅱ diabetes and even Alzheimer's disease.ACAT family enzymes are integral endoplasmic reticulum (ER) membrane proteins and can be divided into ACAT branch and acyl-coenzyme A:diacylglycerol acyltransferase 1 (DGATI) branch according to their substrate specificity.The ACAT branch catalyzes synthesis of cholesteryl esters using long-chain fatty acyl-coenzyme A and cholesterol as substrates,while the DGAT1 branch catalyzes synthesis of triacylglycerols using fatty acylcoenzyme A and diacylglycerol as substrates.In this review,we mainly focus on the recent progress in the structural research of ACAT family enzymes,including their disulfide linkage,membrane topology,subunit interaction and catalysis mechanism.     

Acyl-coenzyme A: cholesterol acyltransferase family

The enzymes of the acyl-coenzyme A: cholesterol acyltransferase (ACAT) family are responsible for the in vivo synthesis of neutral lipids. They are potential drug targets for the intervention of atherosclerosis, hyperlipidemia, obesity, type II diabetes and even Alzheimer’s disease. ACAT family enzymes are integral endoplasmic reticulum (ER) membrane proteins and can be divided into ACAT branch and acyl-coenzyme A: diacylglycerol acyltransferase 1 (DGAT1) branch according to their substrate specificity. The ACAT branch catalyzes synthesis of cholesteryl esters using long-chain fatty acyl-coenzyme A and cholesterol as substrates, while the DGAT1 branch catalyzes synthesis of triacylglycerols using fatty acylcoenzyme A and diacylglycerol as substrates. In this review, we mainly focus on the recent progress in the structural research of ACAT family enzymes, including their disulfide linkage, membrane topology, subunit interaction and catalysis mechanism.     

Characterization of two functional phosphoenolpyruvate/phosphate translocator (PPT) genes in Arabidopsis--AtPPT1 may be involved in the provision of signals for correct mesophyll development

The Arabidopsis thaliana chlorophyll a/b-binding protein underexpressed 1 (cue1) mutant shows a reticulate leaf phenotype and is defective in a plastidic phosphoenolpyruvate (PEP)/phosphate translocator (AtPPT1). A functional AtPPT1 providing plastids with PEP for the shikimate pathway is therefore essential for correct leaf development. The Arabidopsis genome contains a second PPT gene, AtPPT2. Both transporters share similar substrate specificities and are therefore able to transport PEP into plastids. The cue1 phenotype could partially be complemented by ectopic expression of AtPPT2 but obviously not by the endogeneous AtPPT2. Both genes are differentially expressed in most tissues: AtPPT1 is mainly expressed in the vasculature of leaves and roots, especially in xylem parenchyma cells, but not in leaf mesophyll cells, whereas AtPPT2 is expressed ubiquitously in leaves, but not in roots. The expression profiles are corroborated by tissue-specific transport data. As AtPPT1 expression is absent in mesophyll cells that are severely affected in the cue1 mutant, we propose that the vasculature-located AtPPT1 is involved in the generation of phenylpropanoid metabolism-derived signal molecules that trigger development in interveinal leaf regions. This signal probably originates from the root vasculature where only AtPPT1, but not AtPPT2, is present.     

Capsaicin formation in p-fluorophenylalanine resistant and normal cell cultures ofCapsicum frutescens and activity of phenylalanine ammonia lyase

Callus cultures ofCapsicum frutescens capable of producing a maximum of 53 μg capsaicin/g FW were exposed to various levels of p-fluorophenyialanine (PFP) at 100, 400, 1000 and 2000 μM to develop a resistant cell line that over produces capsaicin. After 15 days of culturing on media lacking PFP, cell lines resistant to 100, 400 and 1000 μM registered 18%, 34.5% and 45% increase in capsaicin content over normal cell line (cells not exposed to PFP). Capsaicin accumulation was inhibited in 2000 μM PFP resistant cell line. The profile of phenylalanine ammonia lyase (PAL), the key enzyme in pheny1propanoid pathway in resistant cell cultures was studied and compared with normal cell cultures to understand its role in capsaicin formation. Importantly increased production of capsaicin was obtained using PFP resistant cell lines. The activity profile of PAL had no correlation with capsaicin content in both control and PFP resistant cells.     

Pepper morphological traits related with resistance to Phytophthora capsici

Inheritance of 10 morphological and quantitative traits related to plant and fruit development and resistance to the pathogen Phytophthora capsici was studied in an intraspecific cross between a non-pungent, susceptible Capsicum annuum parent (cv. Americano) and a wild, pungent and resistant line (Serrano Criollo de Morelos-334). Data were obtained from the segregation of 166 F₂ plants and 50 F₃ plants in four years. Three of the traits analyzed (necrosis length, leaf width and leaf length) exhibited a transgressive segregation. A multiple linear regression analysis was applied in order to establish a relationship between necrosis length and some of the morphological traits measured such as length and width of leaf, length, diameter and mass of fruit, capsaicin content in fruits, and presence of hair on leaves and stems. The results identified a linear dependence between necrosis length (as an inverse measurement of resistance) and leaf width, fruit diameter and hair presence in the stem. Pungency was not related with resistance.     

辣椒根系分泌的潜力化感物质对生菜幼苗抗氧化代谢的影响

以盆栽辣椒为试验材料,采用树脂吸附萃取和气质联用仪测定辣椒根系分泌物,分析、确定其中的疑似化感物质。分别使用6种（0、2、4、8、12、16μg·mL-1）不同浓度的外源潜力化感物质处理生菜种子,通过种子发芽、幼苗生长分析其潜力化感作用,并研究其对生菜幼苗抗氧化代谢的影响。结果表明,2,6-二叔丁基苯酚（2,6-DTBP）、邻苯二甲酸二异丁酯（DIBP）和邻苯二甲酸二丁酯（DBP）为辣椒根系分泌的潜力化感物质,随三种潜力化感物质浓度的增加,生菜幼苗的谷胱甘肽（GSH）含量降低,超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、过氧化物酶（POD）、多酚氧化酶（PPO）和抗坏血酸氧化酶（APx）活性先增加后降低。2,6．DTBP、DIBP和DBP4化感抑制作用的低限浓度分别为4、8、8pg·mL-1,三者通过降低GSH含量而损伤生菜幼苗的抗氧化代谢系统。