Sinapoyl glucose

The elucidation of sinapoyl ester metabolism was aided by the availability of mutants. The sngl sinapoyl glucose accumulator 1) mutant of Arabidopsis had been identified based on a mutant screen for alterations in the composition of fluorescent compounds in the leaves. The screen was performed by thin layer chromatography and revealed that the leaves of the sngl mutant contained less sinapoylmalate and instead accumulated the precursor sinapoyl glucose (Lorenzen et al. 1996). 

In lemon, p-coumaric acid, caffeic, ferulic and sinapic are detected in small amounts as well as p-coumaryl, feruloyl and sinapoyl glucose. These phenolic acids are also present in grapefruit, although in this case ferulic acid is the main compound, while in lemon it is p-coumaric acid [16]. 

Bell peppers, both green and red, contain low amounts of phenolic acid derivatives p-Coumaric (< 4 mg/kg), caffeic (< 10 mg/kg), ferulic (<15 mg/kg), sinapic (<5 mg/kg) and vanillic (10 mg/kg) acids [77]. Caffeoyl glucose, feruloyl glucose and sinapoyl glucose are the main hydroxycinnamic acid derivatives found, while no quinic acid derivatives have been detected [63]. Feruloyl glucose may accumulate up to 11 mg/kg f.w. and sinapoyl glucose up to 5 mg/kg in some red cultivars. 

Cis- and trans-sinapine (the choline ester of sinapic acid), sinapic acid, sinapoyl glucose, Kaempferol-sinapoyl-trihexoside 1 -0-P-D-glucopyranosyl sinapate, Sinapoyl-hexoside, Disinapoyl hexoside, trisinapoyl-dihexoside and sinapoyl conjugate... 

Phenolic compounds have sometimes been used to detect adulterations of fruit juices and jams. Most of them are flavonols, but some HCA derivatives can be used since they are typical of some fruit species such as tartaric derivatives in grape. For example, grape juice can be detected by the presence of caffeoyl-, / -coumaroyl-, and feruloyl-tartaric acids, whereas the presence of quinic esters of HCA would imply adulteration with other fruits. A method has also been developed for detection and quantitation of pulpwash, a lower-quality juice product, in orange juice [9] feruloyl and sinapoyl glucose, in addition to different other phenolic compounds, were present in much larger amounts in pulpwash. 

FIGURE 2.1 Structures of (a) sinapic acid, (b) sinapine and (c) sinapoyl glucose identified from rapeseed. 

Free Radical Scavenging Activity of Sinapoyl Glucose,... 

FIGURE 15.5 HPLC chromatograms of 70% methanolic extract of rapeseed meal indicating benzoic acid derivatives (a) at 275 nm and sinapic acid derivatives (b) at 330 nm. Chromatographic conditions elution using water/methanol (90 10) with 1.25% O-phosphoric acid as solvent A and methanol (100%) with 0.1% ( -phosphoric acid solvent B in a C-8 Chrospher column (Knauer). Sinapoyl glucose (GP), sinapine (SP), sinapic acid (SA), others non-identified phenolic constituents. 

The antioxidant activities of standards of sinapoyl glucose, sinapine and sinapic acid, the major sinapic acid derivatives, were compared using the free radical scavenging activity. Under the tested concentrations (Figure 15.8), the free radical scavenging activity followed the order ... 

Sinapic acid > sinapoyl glucose > sinapine cation... 

To scavenge 25 x 10 DPPH radicals, the required concentrations (mM) for sinapic acid, sinapoyl glucose and sinapine cation were 30.8, 35.8 and 47.5 mM, respectively, compared to 21.5 mM for Trolox, a water-soluble antioxidant. 

Thiyam et al. (2006a) were the first to compare the free radical scavenging activity of test compounds sinapic acid with sinapine and sinapoyl glucose using the DPPH... 

FIGURE 15.9 Free radical scavenging activity of sinapic acid (SA), sinapine (SP) and sinapoyl glucose (GP). 

The theoretical contribution of the phenolic constituents, such as free sinapic acid, sinapoyl glucose and sinapine, to the total radical scavenging activity of the extracts is shown in Figure 15.11. The concentration of the phenolic constituents was recorded by HPLC (330 nm). Calibration curves for the RSA were recorded using standard compounds. 

I By sinapoyl glucose By sinapine By sinapic acid By non-identified... 

FIGURE 15.13 DPPH radicals scavenged with 70% methanolic extract of commercial meals. Right to left mustard Delhi, mustard Manipur, meals X, Y, A (non-specified), husk meal, second-pressed first-pressed solvent-extracted and cold-pressed meals. From the same company. Radicals scavenged by phenolic constituents sinapoyl glucose (SG), sinapine (SP), sinapic acid (SA) and rest from un-identified (non-identified) phenolic constituents. 

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