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Ionic Thiocyanate (SCN - ) Production from 4-Hydroxybenzyl Glucosinolate Contained in Sinapis alba Seed Meal

2005; American Chemical Society; Volume: 53; Issue: 22 Linguagem: Inglês

10.1021/jf051570r

1520-5118

V. Borek, Matthew J. Morra,

Plant Parasitism and Resistance

Meal produced from Sinapis alba seed by crushing to remove oil contains a glucosinolate that when hydrolyzed produces phytotoxic allelochemicals; however, the responsible compounds and pathways for their production have not been elucidated. S. alba seed meal and partially purified extracts containing 4-hydroxybenzyl glucosinolate were included in experiments to identify and monitor enzymatically released products using GC−MS and HPLC−MS. The initial product, 4-hydroxybenzyl isothiocyanate, was unstable in aqueous media, showing a half-life of 321 min at pH 3.0, decreasing to 6 min at pH 6.5. More alkaline pH values decrease the stability of 4-hydroxybenzyl isothiocyanate by promoting the formation of a proposed quinone that hydrolyzes to SCN-. Measurement of SCN- showed stoichiometric release from S. alba meal at 48 h when buffered at pH values as low as 4.0, demonstrating that SCN- production in soil is not only probable but likely responsible for observed phytoxicity of the meal. Keywords: Glucosinolates; Sinapis alba; allelochemicals; mustard; phytotoxic; sinalbin