S-alk(en)yl-L-cysteine sulfoxides, alliinase and aroma in Leucocoryne

Levels of S-alk(en)yl-L-cysteine sulfoxides; alliinase and enzymatically ge nerated pyruvic acid were determined in the bulb, leaf and scape of five sp ecies and a natural hybrid of Leucocoryne (Liliaceae), a genus of ornamenta l geophytes indigenous to Chile. ( +)-S-Methyl-L-cysteine sulfoxide (MCSO) was present in all plant parts of all species at levels between 0.09 and 1. 41 mg g(-1) fr. wt. Trans-(+)-S-(1-propenyl)-L-cysteine sulfoxide (PRENCSO) was present in plant parts of three species only (L. angustipetala, L. odo rata and L. purpurea) at levels between 0.12 and 1.82 mg g(-1) fr. wt. No o ther S-alk(en)yl-L-cysteine sulfoxides were detected. Alliinase (EC 4.4.1.4 ) was detected in the leaf, bulb and scape of L. angustipetala and L, purpu rea, only in the leaves of L. coquimbensis and L. purpurea x L. coquimbensi s, and only in the bulb of L. odorata. Enzymatically generated pyruvic acid was detected in all plant parts of all species at levels between trace amo unts and 5.33 mu mol g(-1) fr. wt. As PRENCSO is produced only in Leucocory ne np species exhibiting a strong and unpleasant onion-like aroma, it is pr obable that the enzymatic degradation of PRENCSO is the main cause of that aroma. Consequently, Leucocoryne cultivars should be selected in species an d hybrids that lack the ability to synthesise PRENCSO. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.