Cinnamic acids HPLC separation

However, due to the artifacts resulting from oxidation, hydrolysis of esters or ethers, or isomerization of phenolics during pretreatment of wines, as well as due to the low recovery rates of some phenolics, analysis of wine phenolics via direct injection of the filtered wine into the chromatographic column is often selected (80,82-84). For the red wine and musts (80), which were injected directly into the HPLC without sample preparation, a ternary-gradient system was often employed for phenolic compounds. Twenty-two phenolic compounds, including 10 anthocyanins, were analyzed from red wine. The separation of cinnamic acid derivatives (313 nm),... 

For the red wines (82-84), which were injected directly into the HPLC without sample preparation, a ternary-gradient system using aqueous acetic acid (1% and 5% or 6%), and acidified acetonitrile (acetonitrile-acetic acid-water, 30 5 6) was used for cinnamic acid derivatives, catechins, flavonols, flavonol glycosides, and proanthocyanidins. Due to the large number of peaks, the gradient was extended to 150 min for the resolution of many peaks of important phenolics. This direct injection method was able to separate phenolic acids and esters, catechins, proanthocyanidins, flavonols, flavonol glycosides, and other compounds (such as tyrosol, and rrans-resveratrol) in wine in a single analysis. However, use of acetic acid did not permit the detector (PDA) to be used to record the UV spectra of phenolics below 240 nm (84). 

Fig. 17 HPLC separation of chlorogenic acids from roasted coffee. (From Ref. 143.) 1-15 = hydroxy-cinnamic acids 7, 8 = coumaroylquinic acids 16 = caffeoyltryptophan.

Figure 6. MALDI mass spectrum of fraction 13 from RP-HPLC. The H,K-ATPase-enriched vesicles were trypsinized and centrifuged to separate supernatant from pellet. The supernatant was subjected to RP/HPLC and individual fractions collected and subjected to MALDI/MS. The MALDI mass spectrum (reflectron-ion mode) was obtained using a-cyano-4-hydroxy cinnamic acid as a matrix (Panel A). The signals were assigned to a-subunit peptides (Table 2). The signal at m/z 1798, indicated by an arrow was next subjected to PSD-analysis. The PSD-spectrum of MH+ 1798.4 is shown in Panel B. Only the peaks for the b and y fragment ions are labeled. The deduced amino acid sequence is shown at the top of the panel.

Winterstein esters are easily turned into >-cinnamates by the action of acids (H silica gel) [32]. For preparative purposes the reaction has been carried out using the Hoffmann elimination of the corresponding methylammonium hydroxides [27] or the Cope elimination of the corresponding tf-oxides [SI], The latter procedure is more convenient, since, if the reaction is carried out in THF, elimination of dimethylhydroxylamine takes place spontaneously at room temperature. If only a moderate excess of peracid is employed, the exocyclic double bond at C-4 is not affected [30], The transformation of Winterstein esters into cinnamates can be very useful for separation purposes. Thus, whereas taxine B (2a) and isotaxine B (2b) are difficult to separate by HPLC, their corresponding cinnamates can be separated by column chromatography... 

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