Grape polyphenols, especially hydroxycinnamic acids such as caftaric and caffeic acid, are prone to enzymatic oxidation reactions during the winemaking process, forming o-quinones and leading to color darkening. Glutathione is capable of trapping these o-quinones and thus limiting juice browning. In this study, the addition of glutathione or cysteinylglycine onto caftaric or caffeic acid o-quinones formed by polyphenoloxidase-catalyzed reactions was investigated by UPLC-DAD-ESIMS and NMR data analyses. Complete identification of adducts has been achieved via NMR data. The results confirmed that the favored reaction is the substitution of the sulfanyl group of cysteine at C-2 of the aromatic ring. Several minor isomers, namely, the cis-isomer of the 2-S adduct and trans-isomers of the 5-S and 6-S adducts, and the 2,5-di-S-glutathionyl adducts were also identified and quantified by qNMR. With the exception of 2-(S-glutathionyl)- and 2,5-di(S-glutathionyl)-trans-caftaric acid, these products had never been formally identified. In particular, the 5-S and 6-S derivatives are reported here for the first time. The first formal identification of 2-S cis-derivatives is also provided. Moreover, NMR and UPLC-DAD-ESIMS analysis showed that signature UV and MS spectra can serve as markers of the conformation and substitution position in the aromatic ring for each of the isomers.
Pharmacology, Toxicology and Pharmaceutical Science
1
4%
Business, Management and Accounting
1
4%
Other
0
0%
Unknown
11
42%
Attention Score in Context
Attention Score in Context
This research output has an Altmetric Attention Score of 1. This is our high-level measure of the quality and quantity of online attention that it has received. This Attention Score, as well as the ranking and number of research outputs shown below, was calculated when the research output was last mentioned on 18 September 2016.
All research outputs
#15,384,302
of 22,888,307 outputs
Outputs from Journal of Natural Products
#3,931
of 4,988 outputs
Outputs of similar age
#203,661
of 322,308 outputs
Outputs of similar age from Journal of Natural Products
#23
of 53 outputs
Altmetric has tracked 22,888,307 research outputs across all sources so far. This one is in the 22nd percentile – i.e., 22% of other outputs scored the same or lower than it.
So far Altmetric has tracked 4,988 research outputs from this source. They typically receive more attention than average, with a mean Attention Score of 8.3. This one is in the 15th percentile – i.e., 15% of its peers scored the same or lower than it.
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