F. Richard-forget et al., Isolation and characterization of a 'quinone-trapping' substance from a crude Carica papaya protein preparation, INT J FOOD, 33(3), 1998, pp. 285-296
Citations number
28
Categorie Soggetti
Food Science/Nutrition
Journal title
INTERNATIONAL JOURNAL OF FOOD SCIENCE AND TECHNOLOGY
The oxidation of different phenols [4-methylcatechol, chlorogenic acid, (-)
-epicatechin and (+)-catechin] by endive polyphenoloxidase (PPO) was invest
igated in the presence of an extract from Carica papaya. The occurrence of
cysteine and another 'quinone-trapping' substance in the extract was demons
trated. The unknown substance was purified, as a 4-methylcatechol conjugate
form, by a combination of Bio-gel Pt chromatography and semipreparative hi
gh-performance liquid chromatography (HPLC). Use of liquid chromatography/t
andem mass spectroscopy (LC-MS/MS) equipment and an amino acid analyser all
owed us to identify this agent as a dipeptide cysteine-glutamic acid, comme
rcially available as gamma-Glu-Cys. gamma-Glu-Cys formed one adduct compoun
d with 4-methylcatechol and chlorogenic acid, and two with the flavan-3-ols
. The thiol adducts were not substrates for endive PPO but, in the case of
the 4-methylcatechol conjugate, they acted as competitive PPO inhibitors.