Enzymatic synthesis of new aromatic and aliphatic esters of flavonoids using Candida antarctica lipase as biocatalyst

Enzymatic acylation of rutin and esculin with aromatic, aliphatic and aryl-aliphatic acids using Candida antarctica lipase in tert amyl alcohol as solvent was investigated under low water content. Whatever the acyl donor used, the conversion yields and initial rates for esculin were higher than for rutin. For a given flavonoid, the performance of these reactions depended on the acyl donor structures. For aliphatic acids, conversion yields and initial rates of both flavonoids were respectively in the ranges of 68-90% and of 9.5×10^-2-72×10^-2 mmol l^-1 h^-1. For aromatic acids, the reaction occurred only with the aryl subgroup (cinnamic, hydrocinnamic, 3,4-dihydroxyhydrocinnamic and 4-hydroxyphenyl acetic acids) and was drastically influenced by the presence of side chain and substitution patterns of the aromatic ring. Except for hydrocinnamic acid (75%, 23.4×10^-2 mmol l^-1 h^-1), with these acids the conversion yields and initial rates were lower and in the range of 10-45% and of 0.7×10^-2 to 12.1×10^-2 mmol l^-1 h^-1. Unsaturation of the side chain of the hydrocinnamic acid decreased the esculin conversion rate from 75 to 13% and initial rate from 23.4 to 1.76×10^-2 mmol l^-1 h^-1. The presence of hydroxyl or nitro-groups on the aromatic ring of the aryl aliphatic acid also reduced conversion yields and initial rates. Even without a spacer, the non-phenolic ring acid (quinic acid) was reactive and lead to conversion yields of about 20 and 23% respectively for rutin and esculin.     

Responses of Strawberry (Fragaria × ananassa) to Supplemental UV-B Radiation and Selenium Under Field Conditions

In greenhouse experiments, selenium (Se) has been shown to defend plants against detrimental effects of heavy UV-B radiation stress. The aim of this study was to investigate whether this positive effect can be found in open-field conditions with enhancement of UV-B radiation. In the experiment, conducted with strawberry (Fragaria×ananassa, cultivars “Jonsok” and “Polka”) over two growing seasons, plants were exposed to UV-B radiation (including UV-A) and cultivated without Se or supplied with Se added at two levels (0.1 and 1.0 mg kg⁻¹). The plants were monitored for growth, flavonoids, chlorophyll fluorescence, net photosynthesis as well as tissue and cell structure. Photosystem II was observed to be sensitive to UV-B stress under field conditions. In the leaves, a decrease in F_v/F_m was seen at the end of the growing season, implying a cumulative effect of UV-B stress. Several parameters, especially cell and tissue structures, were affected by UV-B and UV-A treatments, which proves the need for UV-A control in outdoor UV-B supplementation studies. Addition of Se did not ameliorate the harmful effects of UV-B but the lower Se-increment level increased leaf growth. The effects of UV-B and Se differed during the two experimental years, indicating the need to repeat experiments during several growing seasons.     

葡萄叶中总黄酮的提取工艺研究

目的：从葡萄叶中提取总黄酮。方法：采用正交试验法研究葡萄叶总黄酮的最佳提取工艺条件,考察了乙醇浓度、回流温度、回流时间及料液比四因素对葡萄叶总黄酮提取率的影响。结果：确立了葡萄叶总黄酮最佳提取条件为：45％的乙醇为溶剂、液料比为1：40、提取温度为60％、提取时间2h,在最佳工艺条件下葡萄叶总黄酮含量为5．329mg／g。     

麻栎叶黄酮的提取及其抗氧化活性研究

在单因素试验的基础上,对麻栎叶黄酮提取工艺进行优化,并研究了麻栎叶黄酮类化合物的抗氧化活性.结果显示,麻栎叶黄酮提取的最佳工艺是以60％乙醇为提取剂,提取物固液比1∶20,提取温度60℃,提取次数2次,微波功率640W、微波时间2 min,提取时间60 min,黄酮提取率为6.06 mg/g,回收率为96.5％.麻栎叶黄酮类化合物对自由基DPPH·、·OH以及亚硝酸盐的清除率分别达到97.7％、97.6％和94.4％.试验结果表明提取工艺合理,黄酮提取率高,麻栎叶黄酮提取液具有很好的抗氧化活性.     

赶黄草总黄酮树脂精制工艺与检测方法

本研究以总黄酮吸附量和解析率为检测指标,结合动态洗脱考察结果,考察11种树脂对赶黄草总黄酮的富集精制能力。优化树脂类型,选定了对总黄酮进行富集纯化较好的树脂HPD450;采用单因素及正交实验,确定最佳工艺条件:上样量10 mL,以6 mL/min的流速8 BV水、6 BV 80%甲醇溶液洗脱,pH值为6~7。以此方法得到90%以上的赶黄草总黄酮,实验结果良好,总黄酮精制工艺成效显著。用HPLC法精确测定赶黄草中槲皮苷、PGHG和ThA三个指标性黄酮成分,最佳色谱条件为:C18色谱柱,检测波长280 nm,进样量5μL,流动相:乙腈-0.05%磷酸溶液(0~25 min:12%~45%乙腈;25~40 min:45%~70%乙腈)梯度洗脱;精确测定赶黄草全草中3种黄酮成分的含量。采用分光光度法检测,指导优化总黄酮精制工艺,并以HPLC法精确测定三种黄酮代表成分。比较两种方法测定结果相一致,互为补充;故在工业生产时,可以分光光度法指导生产,以HPLC法精确定量测定。     

藜叶中黄酮类化合物体外抗氧化活性研究

为了探讨藜叶中黄酮类化合物的体外抗氧化活性,采用有机溶剂提取法和色谱柱法对藜叶中化学成分进行提取与分离;以Vc作对照,对分离纯化的芦丁、乙酸乙酯浸膏和正丁醇浸膏进行DPPH·、O2^-·和·OH的清除效果试验。结果表明：三者对DPPH·、O2^-·、·OH均具有清除作用,且与浓度呈量效关系,芦丁对·OH清除效果优于Vc,芦丁具有较强的清除DPPH·能力,其IC50为0．05μg／mL。     

Characterisation of polyphenols by HPLC-PAD-ESI/MS and antioxidant activity in Equisetum telmateia

The antioxidant activity of an aqueous extract (infusion) and respective ethyl acetate fraction of Equisetum telmateia Ehrh. (Equisetaceae), a plant used in traditional medicine for its anti-inflammatory and diuretic properties, has been evaluated by DPPH, TEAC and TBARS assays. A high and significant antioxidant activity was detected in the ethyl acetate fraction. Analysis of the aqueous extract and the ethyl acetate fraction by HPLC-PAD-ESI/MS allowed the identification of the major phenolic compounds as flavan-3-ol, kaempferol and phenolic acid derivatives. Among the flavan-3-ols, A-type proanthocyanidins and afzelechin derivatives were detected as well as the more common B-type procyanidins, B2 and C1, whose identification was further confirmed by HPLC using detection involving chemical reaction with p-dimethylamino-cinnamaldehyde. The results suggest that the anti-inflammatory activity of E. telmateia could be due, at least in part, to the presence of compounds with antioxidant activity.     

基于代谢组学分析黑老虎植株不同部位黄酮类成分

黑老虎的根是常用中药,黄酮类化合物是药用植物的主要活性成分之一。为探究黑老虎植株叶和茎中可能含有与根类似或具有高度富集的类黄酮化合物,挖掘其利用价值。该文利用广泛靶向代谢组学技术,鉴定了黑老虎的叶、茎和根的代谢物,并根据结构配置分类,解析其中类黄酮的多样性和丰度。结果表明：(1)黑老虎叶中类黄酮数量(80个)>茎(73个)>根(67个),3个部位均有61个相同的黄酮类化合物,叶和茎中含有更多的黄酮醇类化合物,从而使类黄酮多样性高于根。(2)在3个部位积累量比较高的是黄酮醇类、黄酮类、黄烷醇类和查尔酮类,其中黄酮醇和黄酮在茎和根积累量下降,导致类黄酮丰度从叶(24.00×10⁷)-茎(13.45×10⁷)-根(9.05×10⁷)连续大幅度下调。(3)叶和茎中含有大量与根相同和多种根中没有的类黄酮,可以考虑替代或互补利用,3个部位儿茶素类化合物表达量都较高,叶中还富含槲皮素及其衍生物,具有较高的利用价值。     

Human urine: Epicatechin metabolites and antioxidant activity after cocoa beverage intake

Associations between cocoa consumption in humans, excreted metabolites and total antioxidant capacity (TAC) have been scarcely investigated. The aims of the study were to investigate the epicatechin (( ? )-Ec) metabolites excreted in urine samples after an intake of 40 g of cocoa powder along with the TAC of these urine samples and the relation between both the analyses. Each of the 21 volunteers received two interventions, one with a polyphenol-rich food (PRF) and one with a polyphenol-free food (PFF) in a randomized cross-over study. Urine samples were taken before and during 24 h at 0–6, 6–12 and 12–24 h periods after test intake. The excreted ( ? )-Ec metabolites and the TAC were determined in urine samples by LC-MS/MS and TEAC assay, respectively. The maximum excretion of ( ? )-Ec metabolites and the maximum TAC value were observed in urine samples excreted between 6 and 12 h after PRF consumption. Significance of TAC increase was found in urine samples excreted during 0–6 and 6–12 h (66.6 and 72.67%, respectively, with respect to the 0 h).     

Genetical metabolomics of flavonoid biosynthesis in Populus: a case study

Genetical metabolomics [metabolite profiling combined with quantitative trait locus (QTL) analysis] has been proposed as a new tool to identify loci that control metabolite abundances. This concept was evaluated in a case study with the model tree Populus. Using HPLC, the peak abundances were analyzed of 15 closely related flavonoids present in apical tissues of two full-sib poplar families, Populus deltoides cv. S9-2 x P. nigra cv. Ghoy and P. deltoides cv. S9-2 x P. trichocarpa cv. V24, and correlation and QTL analysis were used to detect flux control points in flavonoid biosynthesis. Four robust metabolite quantitative trait loci (mQTL), associated with rate-limiting steps in flavonoid biosynthesis, were mapped. Each mQTL was involved in the flux control to one or two flavonoids. Based on the identities of the affected metabolites and the flavonoid pathway structure, a tentative function was assigned to three of these mQTL, and the corresponding candidate genes were mapped. The data indicate that the combination of metabolite profiling with QTL analysis is a valuable tool to identify control points in a complex metabolic pathway of closely related compounds.