γ-glutamyl peptides from Allium sativum bulbs

Four γ-glutamyl peptides were isolated from a hydrophilic extract of garlic bulbs. γ- l-Glutamyl- S-( trans-1-propenyl)- l-cysteine has been isolated as a new genuine constituent of Allium sativum. For the first time detailed NMR data for γ- l-glutamyl- S-allyl- l-cysteine, γ- l-glutamyl- S-( trans-1-propenyl)- l-cysteine and γ- l-glutamyl- S-allylthio- l-cysteine are reported. The structures of the four compounds were established on the basis of their spectral data (IR, FABMS, 1H and 13C NMR). Extensive 2D heteronuclear correlated NMR experiments allowed the assignment of all proton and carbon resonances for all reported compounds.