Effects of metal ions on benzylglucosinolate degradation in Lepidium sativum seed autolysates

Abstract

The effects of varying concentrations of Fe 2+ (5 × 10 −5 −5 × 10 −1 M) on benzylglucosinolate degradation in Lepidium sativum seed autolysates were investigated. Increased glucosinolate decomposition was observed over the whole range with a maximum effect at ca 6 × 10 −3 M Fe 2+, at which point glucosinolate degradation was more than three times that obtained in the absence of added Fe 2+ . Nitrile formation was especially enhanced in the presence of all concentrations of Fe 2+ studied, and maximum amounts were obtained at ca 6 × 10 −3 M Fe 2+ when a more than four-fold increase over quantities produced in the absence of Fe 2+ was observed. Thiocyanate formation was also promoted with a maximum at ca 4 × 10 −3 M Fe 2+, but isothiocyanate production was considerably reduced in allcases. It is suggested that Fe 2+ inhibits isothiocyanate formation by interfering with the availability of ascorbic acid which is a proven co-factor for most thioglucosidase isoenzymes, but that an Fe 2+-ascorbate complex might then be responsible for promoting enzymic production of nitrile. The effects of a limited range of concentrations of Fe 3+ and Cu + were also studied, and results related to those for Fe 2+. The relevance of the findings to natural systems and to glucosinolate-containing foods is briefly discussed.