Isolation, structure determination, and sensory activity of mouth-drying and astringent nitrogen-containing phytochemicals isolated from red currants (Ribes rubrum).
Application of chromatographic separation and taste dilution analyses recently revealed, besides a series of flavon-3-ol glycosides and (E)/(Z)-aconitic acid, four nitrogen-containing phytochemicals as the key astringent and mouth-drying compounds in red currants (Ribes rubrum). The isolation and structure determination of the astringent indoles 3-carboxymethyl-indole-1-N-beta-D-glucopyranoside (1) and 3-methylcarboxymethyl-indole-1-N-beta-D-glucopyranoside (2), as well as the astringent, noncyanogenic nitriles 2-(4-hydroxybenzoyloxymethyl)-4-beta-D-glucopyranosyloxy-2(E)-butenenitrile (3) and 2-(4-hydroxy-3-methoxybenzoyloxymethyl)-4-beta-D-glucopyranosyloxy-2(E)-butenenitrile (4) by means of 1D/2D NMR, LC-MS/MS, and UV-vis spectroscopy are reported. The structures of compounds 1 and 2 were confirmed by synthesis. Using the recently developed half-tongue test, human recognition thresholds for the astringent and mouth-drying nitrogen compounds were determined to be between 0.0003 and 5.9 micromol/L (water). In particular, the extraordinarily low threshold of 0.0003 micromol/L evaluated for the indole 1 represents the lowest recognition threshold of any astringent phytochemical reported to date.
Schwarz
Bernd
B
Institut für Lebensmittelchemie, Universität Münster, Corrensstrasse 45, D-48149 Münster, Germany.
Hofmann
Thomas
T
D001252:Astringents; D005638:Fruit / Q000737:chemistry*; D006801:Humans; D007211:Indoles / Q000032:analysis*; D009570:Nitriles / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis*; D017672:Nitrogen Compounds / Q000494:pharmacology; D031965:Ribes / Q000737:chemistry*; D013649:Taste; D014987:Xerostomia / Q000139:chemically induced
D001252:Astringents; D007211:Indoles; D009570:Nitriles; D017672:Nitrogen Compounds; D009584:Nitrogen