Grape reaction product

The grape reaction product (GRP, GRP1 or 2-S-glutathionyl caftaric acid^[1]) is a phenolic compound explaining the disappearance of caftaric acid from grape must during processing.^[2] It is also found in aged red wines.^[3] Its enzymatic production by polyphenol oxidase is important in limiting the browning of musts,^[4] especially in white wine production. The product can be recreated in model solutions.^[5][6]

Grape reaction product

Chemical structure of grape reaction product
Names
IUPAC name 2-[(E)-3-[3-[2-[(4-amino-4-carboxybutanoyl)amino]-3-(carboxymethylamino)-3-oxopropyl]sulfanyl-4,5-dihydroxyphenyl]prop-2-enoyl]oxy-3-hydroxybutanedioic acid
Other names GRP GRP1 2-S-Glutathionyl caftaric acid
Identifiers
3D model (JSmol)	Interactive image
ChEBI	CHEBI:147433
PubChem CID	71308212
InChI InChI=1S/C23H27N3O15S/c24-10(21(35)36)2-3-14(28)26-11(20(34)25-7-15(29)30)8-42-13-6-9(5-12(27)17(13)32)1-4-16(31)41-19(23(39)40)18(33)22(37)38/h1,4-6,10-11,18-19,27,32-33H,2-3,7-8,24H2,(H,25,34)(H,26,28)(H,29,30)(H,35,36)(H,37,38)(H,39,40)/b4-1+ Key: GYXGDEQYOIGEEQ-DAFODLJHSA-N
SMILES Oc1cc(cc(c1O)SCC(NC(=O)CCC(N)C(=O)O)C(=O)NCC(O)=O)\C=C\C(=O)OC(C(O)=O)C(O)C(O)=O
Properties
Chemical formula	C23H27N3O15S
Molar mass	617.54 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Determining its concentration in wine is possible by mass spectrometry.^[7]

S-Glutathionyl caftaric acid is itself oxidizable.^[8] It is not a substrate for grape polyphenol oxidase, but laccase from Botrytis cinerea can use it to form GRP2.^[9]

Related molecules

Other related molecules are trans-caffeoyltartrate derivatives like GRP o-quinone^[10] and 2,5-di-S-glutathionyl cafteoyl tartrate (GRP2)^[11] or adducts with anthocyanidins.^[12]

Caftaric acid UV visible spectrum

See also

• Phenolic compounds in wine