Use of Grasshoppers in Bioassay of Thioglucosides in Rapeseed (Brassica napus)

Abstract

THE thioglucoside content of rapeseed (Brassica spp.) varies considerably depending on variety¹, environmental conditions (ref. 2 and unpublished work of R. K. Downey and L. R. Wetter), and species³. The seeds contain the following thioglucosides: gluconapin, glucobrassiconapin and progoitrin, and the enzyme myrosinase which can hydrolyse these thioglucosides respectively to 3-butenyl, 4-pentenyl and 2-hydroxy-3-butenyl isothiocyanates⁴ (ITC). The 2-hydroxy-3-butenyl ITC is not stable and following cyclization produces 5-vinyl-2 oxazolidinethione, commonly called goitrin. Previous investigations showed that these compounds are responsible for depression of growth and thyroid enlargement in non-ruminant animals⁵. Because rapeseed meal is used as a protein supplement in feeding livestock, it would be desirable either to reduce or completely to eliminate these thioglucosides from rape-seed⁶.