Abstract:

The aim of this study was to compare the specific activity of myrosinases from the seeds of seven cruciferous
plants, and the composition of glucosinolates in rapeseed meal degraded by these different myrosinases were determined by
gas chromatography-mass spectrometry (GC-MS). The results showed that the specific activities of seven myrosinases were
significantly different (P ＜ 0.05) and followed the descending order: broccoli seeds (BSm) ＞ rapeseeds (RPSm) ＞ white
cabbage seeds (WCSm) ＞ radish seeds (RDSm) ＞ kale seeds (KSm)＞ cabbage seeds (CSm) ＞ mustard seeds (MSm).
Six compounds were detected in the degraded products by myrosinase from RPS (RPSm): 1-butene,4-isothiocyanate, allyl
isothiocyanate, benzene,2-ethyl,isothiocyanate, benzenepropane nitrile, goitrin and 2,1-benzisoxazole. The highest content (33.22%)
of 1-butene,4-isothiocyanate was found in the degraded products by myrosinase from CS (CSm), which was more than the content
of 32.20% by RPSm. Besides, under the same experimental conditions, this compound was not detected in the degraded products
by myrosinase from MS (MSm). Butane,1-isothiocyanate was a new compound found in the degraded products by myrosinases
from WCS, KS , MS and CS. Comparing with RPSm, four new oxazoles and three new nitrils but not 2,1-benzisoxazole were
found in the degraded products by six other myrosinases. Under the same condition, the glucosinolates degradation products
generated by RPSm and other myrosinases were significantly different. The specific activity of RPSm was lower than that of BSm,
but the sorts and contents of oxazoles and nitriles in its degradation products were the least. It can be concluded that RPSm is the
appropriate myrosinase source to degrade the glucosinolates in rapeseed meal.

Key words: myrosinase, rapeseed meal, gas chromatography-mass spectrometry (GC-MS), glucosinolates