A new pyridine cysteine-sulphoxide identified in Allium stipitatum

Allium stipitatum Regel is known as ornamental plant in Europe. In Central Asia it is used as spice and in folk medicine and known as „Musir“ or „Anzur“. Allium stipitatum belongs to subgenus Melanocrommyum section Megaloprason. A newly developed HPLC-MS/MS method was used for screening on amino acids, amines and sulphoxides. Amino acid derivatives were analysed as corresponding o-phthaldialdehyde derivatives. Besides the already described cysteine sulphoxide methiin, a new compound was identified, which is a 2 pyridyl-S-L-cysteine sulphoxide (Figure). Structure elucidation was performed by HRESI, NMR, IR and polarometric measurements. This compound could also be found in further members of the section Megaloprason and is probably useful as chemical marker for this group. Interestingly, the recently described 3 pyrrol-S-(+)-L-cysteine sulphoxide [1], which is also characteristic for the subgenus Melanocrommyum, could not be found in these species carrying the corresponding pyridine derivative. It can be assumed that both biogenetic pathways are excluding each other. Additionally to the above described structure elucidation, the alliinase of A. stipitatum could be partially characterized.

Reference: [1] Jedelská, J. et al (2008)J. Agric. Food Chem. 56:1465–1470.