Factors affecting the dissolution and degradation of oriental mustard-derived sinigrin and allyl isothiocyanate in aqueous media

Sinigrin, the predominant glucosinolate in the oriental mustard Brassica ju ncea, is mainly degraded upon the enzymatic action of myrosinase under norm al conditions to give allyl isothiocyanate (AITC) in an aqueous media. Beca use AITC is considered to be the principal nematicidal ingredient in B, jun cea, its stability in aqueous media is an important issue in achieving effi cient nematode control. Pure sinigrin and AITC were found to be relatively stable in buffered water in the pH range of 5.00-7.00 but less stable at pH 9.00. Both sinigrin and AITC mere more stable in soil water (supernatant o f a 1:1 water/air-dried soil mixture) than in buffered water at the same pH range of 5.00-9.00. Sinigrin dissolved from the mustard bran or ground see d into water very quickly and was degraded by codissolved myrosinase to AIT C. The AITC that formed From the degradation of sinigrin was found to be mo re stable in the soil water than in the buffered water. Buffer capacity was considered to be one of the factors that contributed to the stabilization of AITC in the soil water, but other unknown factors from both bran or seed and soil may also have contributed to the stabilization.