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Vereinfachte simultane Darstellung einer systematischen Serie von Mono‐ und Di‐(Hydroxy)zimtsäuretartraten
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Phenolic acids represent about one-third of the dietary phenols and are widespread in vegetable and fruits. Several plants belonging to both vegetables and medical herbs have been studied for their hydroxycinnamic acid content. Among them, Echinacea purpurea is preferentially used for caffeic acid-derivatives extraction. The wine industry is a source of by-products that are rich in phenolic compounds. This work demonstrates that unripe grape juice (verjuice) presents a simple high-pressure liquid chromatography (HPLC) profile for hydroxycinnamic acids (HCAs), with a great separation of the caffeic-derived acids and a low content of other phenolic compounds when compared to E. purpurea and other grape by-products. Here it is shown how this allows the recovery of pure hydroxycinnamic acids by a simple and fast method, fast protein liquid chromatography (FPLC). In addition, verjuice can be easily obtained by pressing grape berries and filtering, thus avoiding any extraction step as required for other vegetable sources. Overall, the proposed protocol could strongly reduce the engagement of solvent in industrial phenolic extraction.
Hydroxycinnamic acids (HCAs) are important natural phenolic compounds present in high concentrations in fruits, vegetables, cereals, coffee, tea and wine. Many health beneficial effects have been acknowledged in food products rich in HCAs; however, food processing, dietary intake, bioaccessibility and pharmacokinetics have a high impact on HCAs to reach the target tissue in order to exert their biological activities. In particular, metabolism is of high importance since HCAs’ metabolites could either lose the activity or be even more potent compared to the parent compounds. In this review, natural sources and pharmacokinetic properties of HCAs and their esters are presented and discussed. The main focus is on their metabolism along with biological activities and health benefits. Special emphasis is given on specific effects of HCAs’ metabolites in comparison with their parent compounds.
The Echinacea-derived immunostimulator and HIV-1 integrase inhibitor (−)-chicoric acid (=2,3-bis{[3-(3,4-dihydroxyphenyl)-1-oxoprop-2-enyl]oxy}butanedioic acid; 1a) was conveniently prepared via a silane-promoted Pd-mediated chemoselective hydrogenolysis of its perbenzylated derivative 12a, which was generated from an efficient and reliable carbodiimide-mediated coupling reaction between the caffeic acid dibenzyl ether derivative 7 and commercially available (+)-dibenzyl L-tartrate (9a). The other naturally occurring dextrorotatory chicoric acid (1b) can be similarly prepared.
Formation of wine thiol precursors is a dynamic process, which can be influenced by vineyard and winery processing operations. With the aim of increasing thiol precursor concentrations, a study of the effects of storing machine-harvested Sauvignon blanc grapes prior to crushing and pressing was undertaken on a commercial scale. 3-Mercaptohexan-1-ol (3-MH) precursors, 2-S-glutathionylcaftaric acid (grape reaction product, GRP), glutathione (GSH) and a number of C6 compounds were assessed at several time points during the experiment. The concentration of the cysteine precursor to 3-MH doubled within 8 h and tripled after 30 h while the GSH and cysteinylglycine precursors increased in concentration roughly 1.5 times. (E)-2-Hexenal and GSH levels decreased as thiol precursors, GRP and C6 alcohols increased during storage. Principal component analysis revealed that precursors contributed to most of the variation within the samples over the storage period, with additional influence, primarily from GSH and GRP, as well as (E)-2-hexenal and (Z)-3-hexen-1-ol. Early storage time points were associated with higher concentrations of GSH and some unsaturated C6 compounds while longer storage times were most closely associated with higher thiol precursor and GRP concentrations. This study provides a detailed overview of interactions related to thiol precursor formation on a commercial scale and highlights the ability to manipulate precursor concentrations prior to grape crushing.
Phenolic acid compounds seem to be universally distributed in plants. They have been the subject of a great number of chemical, biological, agricultural, and medical studies. Hydroxycinnamic acid compounds occur most frequently as simple esters with hydroxy carboxylic acids or glucose, while the hydroxybenzoic acid compounds are present mainly in the form of glucosides. Furthermore, phenolic acids may occur in food plants as esters or glycosides conjugated with other natural compounds such as flavonoids, alcohols, hydroxyfatty acids, sterols, and glucosides. Also, hydroxycinnamic acid amides appear to be common constituents. The occurrence of the different natural phenolic acid compounds in foods is reviewed, and data of the content in fruit, vegetables, and spices are given. The distribution of the main phenolic acid compounds in food plants as well as their changes during development and maturation of fruits are considered. Furthermore, the hydroxycinnamic acids bound to cell wall polymers, the phenolic acid compounds in coffee, cereals, oil seed, and tree nuts, and the analysis of phenolic acid derivatives are reviewed.