Ionic thiocyanate (SCN-) production from 4-hydroxybenzyl glucosinolate contained in Sinapis alba seed meal.
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.
Borek
Vladimir
V
Soil & Land Resources Division, P.O. Box 442339, University of Idaho, Moscow, ID 83844-2339, USA.
Morra
Matthew J
MJ
D002851:Chromatography, High Pressure Liquid; D004355:Drug Stability; D008401:Gas Chromatography-Mass Spectrometry; D005961:Glucosinolates / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D012639:Seeds / Q000737:chemistry* / Q000378:metabolism; D031226:Sinapis / Q000737:chemistry* / Q000378:metabolism; D013861:Thiocyanates / Q000378:metabolism*
C097342:4-hydroxybenzylglucosinolate; D005961:Glucosinolates; D013861:Thiocyanates; C031760:thiocyanate