DMACA

DMCA assay is used to quantify catechins, and it is based on the formation of a green chromophore between catechin and 4-(dimethylamino)-cinnamaldehyde (DMACA) (Polster and others 2003). 

Fig. 3.5 Standard curves of epicatechin and cyanidin-3-O-gfucoside with DMACA reagent...

Fig. 3.7 Normal-phase-HPLC chromatograms of PA fractions generated by differential solvent extraction of crude GSE (protocol 1). (a) Fraction 1, (b) Fraction 2, (c) Fraction 3, (d) Fraction 4, (e) Fraction 5, and (f) Fraction 6. Compounds were detected with post-column deiivatization using DMACA...

C, coumarin BA, bianthryl DMACA, 7-dimethylaminocoumarin-4-acetate-ion DMAPS, 4,4 -(dimethylamino) phenyl sulfone ADMA, 4-(9-anthryl)-/V,lV-dimethy]aniline. 

The following functional group assays are used proanthocyanidin assay, vanillin assay and dimethylaminocinnamaldehyde (DMACA) assay. Details to the experimental designs are listed in Tab. (3.1) to (3.3). 

Protocols use beer, barley and hops d for 0.1 % DMACA in 25 % concentrated hydrochloric acid in methanol 0.3 % DMACA in 25 % concentrated hydrochloric acid in methanol 147,148,291 3 ... 

The use of dimethylaminocinnamaldehyde (DMACA) as a reagent for the colorimetric determination of flavanols was first described by Thies and Fischer [146]. The first protocol was developed by Me Murrough and Me Dowell [147] for purified extracts of barley and hops (Humulus lupulus). The reaction scheme is the same as for the vanillin reaction. The reactivity of proanthocyanidins essentially again resides in the 5,7-hydroxylation of the aromatic A-ring, a single bond between C2 and C3 and the lack of a... 

Catechin is generally used as a standard in the DMACA assay. Calibration plots are linear and therefore, calibration factors are also applied [148]. Like in all conventional methods the use of purified procyanidins as a standard will give the correctest estimates. A blank, composed of the samples without the chromogen reagent, is also... 

Unfortunately, there exist a variety of different protocols. None of these protocols is generally accepted as an universal method. The assay of Delcour and Janssens de Varebeke [148] has been adopted by the European Brewery Convention Analysis Committee as an official method, but a new protocol has recently been published for the analysis of beer [31]. To our knowledge, one of the most carefully optimized DMACA protocols at this time is the one of Li et al. [67] for the analysis of forage legumes. 

In the past few years considerable attention has also been given to the use of the DMACA reagent as a histochemical stain in the analysis of procyanidin containing cells [67,153] and as a post-column derivatization reagent in HPLC analysis of procyanidins (see section chromatography) [151,154],... 

Figure 19.2 Sortinl affects flavonoid transport to the vacuole, (a) Seed coat colors of different slh mutants, (b) DMACA staining shows that some slh mutants (2-50, 2-21, and 10-27) have defects in vacuolar accumulation of proanthocyanidins in the seed coats, (c-e) The recessive mutant slh2-50 is allelic to tt4, a flavonoid biosynthesis mutant that also affects vacuole morphology. The localization of EGFP-5TIP in...

FIGURE 17.6 Mass spectra of procyanidin B2 (a) and (—)-epicatechin (b) obtained from chocolate sample test solntion after elution of zones from the HPTLC cellulose plate developed in water. Here, bands are visualized by postchromatographic derivatization with DMACA detection reagent. 

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