Seasonal variations of the glucosinolate amounts in Brassica campestris L.spp. chinensis

Total and individual glucosinolate concentrations were determined in three chinese Brassica varieties (Brassica campestris L. spp. chinensis var. comm unis Tsen ct Lee (Pak Choi), var. utilis Tsen et Lee (Choi Sum), and var. t ai-tsai Hort. (Tai Tsai)) cultivated at different seasons in greenhouse or in field in order to test their inner quality for the production in Germany . Cultivation in greenhouse has been during winter/spring (S1) and autum/wi nter (S4) whereas cultivation in field was in spring/summer (S2) and summer /autum (S3). The cultivation time of each variety (sowing to harvesting) wa s 8 weeks for S1, S2 and S3, and about 15 weeks for S4. Total glucosinolate amounts were lowest in S4 and highest in S2. From the different varieties, Choi Sum had the highest total concentration in each season, followed by T ai Tsai and Pak Choi. Generally, the glucosinolate amounts positively corre lated with the dry matter content of the individual vegetable. Together, 8 individual glucosinolates were found in each variety. Major components were gluconapin, glucobrassicanapin, neoglucobrassicin, and glucobrassicin, whe reas progoitrin, 4-hydroxyglucobrassicin, gluconasturtiin, and 4-methoxyglu cobrassicin occurred as minor compounds.