Ionic Thiocyanate (SCN^-) Production from 4-Hydroxybenzyl Glucosinolate Contained inSinapis albaSeed Meal

Abstract

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.

Impact of Indian Mustard (Brassica juncea) and Flax (Linum usitatissimum) Seed Meal Applications on Soil Carbon, Nitrogen, and Microbial Dynamics

“…Samples were first defatted with one extraction and two rinses of petroleum ether by vacuum filtration. Defatted material was weighed (300 mg) into 50 mL centrifuge tubes to which 500 mg of 5-mm glass beads [35] were added and then immediately vortexed. A hot (70…”

Evaluating Mustard Seed Meal for Weed Suppression in Potato (Solanum tuberosum)

“…The use of products derived from natural sources to control pests is appealing, and developing new uses for MSM may increase the profitability of biodiesel production (Brown, 2006;Cai & Gu, 2016). MSM contains glucosinolates that typically undergo enzymatic hydrolysis to isothiocyanates, SCN2, nitriles, and other compounds when added to moist soil (Brown, Morra, McCaffrey, Auld, & Williams, 1991;Borek & Morra, 2005;Vaughn & Berhow, 2005). The predominant glucosinolate in S. alba seed is 4-hyroxybenzyl glucosinolate or sinalbin, which ultimately yields SCN2, a compound partly responsible for herbicidal activity of MSM (Daxenbichler, Spencer, Carlson, Rose, Brinker, & Powell, 1991;Borek & Morra, 2005;Hansson, Morra, Borek, Snyder, Johnson-Maynard, & Thill, 2008).…”

“…MSM contains glucosinolates that typically undergo enzymatic hydrolysis to isothiocyanates, SCN2, nitriles, and other compounds when added to moist soil (Brown, Morra, McCaffrey, Auld, & Williams, 1991;Borek & Morra, 2005;Vaughn & Berhow, 2005). The predominant glucosinolate in S. alba seed is 4-hyroxybenzyl glucosinolate or sinalbin, which ultimately yields SCN2, a compound partly responsible for herbicidal activity of MSM (Daxenbichler, Spencer, Carlson, Rose, Brinker, & Powell, 1991;Borek & Morra, 2005;Hansson, Morra, Borek, Snyder, Johnson-Maynard, & Thill, 2008). MSM applied at rates ranging from 113 to 450 g m -2 to the soil surface of container-grown ornamentals reduced annual bluegrass (Poa annua L.), common chickweed [Stellaria media (L.) Vill.…”

Bioherbicides in Organic Horticulture

“…The MSM contains glucosinolates (GLS) that can be enzymatically hydrolyzed to isothiocyanates, thiocyanate (SCN´), nitriles, and other compounds. These biologically active compounds are toxic to many weed species [35,36]. Applying MSM to the soil surface of containers at 113, 225, and 450 g¨m 2 reduced the number of annual bluegrass seedlings by 60%, 86%, and 98%, respectively [31].…”