Allyl Thiocyanate Research Articles

Comparative Analysis of Volatile Flavor Compounds in Seven Mustard Pastes via HS-SPME-GC-MS.

To identify the volatile flavor components in mustard paste (MP), the volatile compounds in seven MPs available on the market were isolated and analyzed by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry. A total of 27 volatile constituents were found by mass spectra and retention index compared to the data obtained from reference compounds or the related literature and databases; these compounds included nine esters, three sulfur-containing compounds, two nitriles, three ketones, three alkenes, and seven other compounds. Of the 27 compounds, 6 compounds came from the turmeric added to MPs. Among the components detected, some compounds derived from AITC were allyl thiocyanate, carbon disulfide, allyl mercaptan, diallyl sulfide, and diallyl disulfide. The results obtained provide a better and comprehensive recognition of the volatile flavor compounds in MPs, and have some reference values for developing and applying isothiocyanate compounds.

Organic thiocyanates - glucosinolate enzymatic degradation products or artefacts of the isolation procedure?

Glucosinolates are abundant in plants of the order Brassicales, and they are degraded by myrosinases into various organic breakdown products: isothiocyanates, thiocyanates, nitriles, etc., depending on their structure, conditions of hydrolysis, the presence of certain protein cofactors. Their most common hydrolysis products are isothiocyanates, while simple nitriles, epithionitriles, and thiocyanates are produced occasionally. Organic thiocyanates are described from a very limited number of Brassicales taxa. Up to now benzyl, (4-hydroxyphenyl)methyl, (4-methoxyphenyl)methyl, 4- methylthiobutyl, and allyl thiocyanates were reported as products of glucosinolates autolysis. The present review summarizes the knowledge on the mechanism of organic thiocyanate formation from the corresponding thioglucosides. The enzymatic formation of organic thiocyanates is believed to be enabled by thiocyanate-forming protein (TFP), but they could be formed via metabolic routes that do not involve TFP. All of the reported thiocyanates are produced from stable (carbo)cationic species that allow an isomerization of an isothiocyanate to thiocyanate, and vice versa. Although the possibility that thiocyanates can be biosynthesized in plats under certain conditions cannot be dismissed, allyl thiocyanate can be a thermal isomerization artefact of the original isothiocyanate that is formed in the heated zones of the gas chromatograph, while other thiocyanates could form in an aqueous medium via heterolytic dissociation to ambident nucleophilic SCN- and its recapture. One should always be aware of this analytical shortcoming when concluding on the presence and quantity of these specific (iso)thiocyanantes in the analyzed sample.

Diversified glucosinolate metabolism: biosynthesis of hydrogen cyanide and of the hydroxynitrile glucoside alliarinoside in relation to sinigrin metabolism in Alliaria petiolata.

Alliaria petiolata (garlic mustard, Brassicaceae) contains the glucosinolate sinigrin as well as alliarinoside, a γ-hydroxynitrile glucoside structurally related to cyanogenic glucosides. Sinigrin may defend this plant against a broad range of enemies, while alliarinoside confers resistance to specialized (glucosinolate-adapted) herbivores. Hydroxynitrile glucosides and glucosinolates are two classes of specialized metabolites, which generally do not occur in the same plant species. Administration of [UL-14C]-methionine to excised leaves of A. petiolata showed that both alliarinoside and sinigrin were biosynthesized from methionine. The biosynthesis of alliarinoside was shown not to bifurcate from sinigrin biosynthesis at the oxime level in contrast to the general scheme for hydroxynitrile glucoside biosynthesis. Instead, the aglucon of alliarinoside was formed from metabolism of sinigrin in experiments with crude extracts, suggesting a possible biosynthetic pathway in intact cells. Hence, the alliarinoside pathway may represent a route to hydroxynitrile glucoside biosynthesis resulting from convergent evolution. Metabolite profiling by LC-MS showed no evidence of the presence of cyanogenic glucosides in A. petiolata. However, we detected hydrogen cyanide (HCN) release from sinigrin and added thiocyanate ion and benzyl thiocyanate in A. petiolata indicating an enzymatic pathway from glucosinolates via allyl thiocyanate and indole glucosinolate derived thiocyanate ion to HCN. Alliarinoside biosynthesis and HCN release from glucosinolate-derived metabolites expand the range of glucosinolate-related defenses and can be viewed as a third line of defense, with glucosinolates and thiocyanate forming protein being the first and second lines, respectively.

Herbicidal activity of glucosinolate-containing seedmeals

Defatted seedmeals from 15 glucosinolate-containing plant species were analyzed for herbicidal activity by determining inhibition of seedling emergence when added to a sandy loam soil containing wheat and sicklepod seeds at concentrations of 0.1, 0.5, and 1% (w/w). In general, the seedmeals were more phytotoxic to wheat than sicklepod. For wheat, all of the seedmeals significantly inhibited seedling emergence at the 1.0% concentration. At the 0.1% concentration three of the seedmeals (Indian mustard, money plant, and field pennycress) completely inhibited wheat emergence. For sicklepod emergence, eight of the seedmeals were completely inhibitory at the 1% level (Indian mustard, field pennycress, garden rocket, Siberian wallflower, English wallflower, garden cress, sweet alyssum, and evening stock) and four were completely inhibitory at the 0.5% level (brown mustard, garden rocket, English wallflower, and sweet alyssum). Intact glucosinolates and their corresponding hydrolysis products varied among the seedmeals with the highest activity. Major hydrolysis products produced by the seedmeals with the most phytotoxicity, respectively, included 2-propenyl (allyl) isothiocyanate (AITC) by brown mustard seedmeal, allyl thiocyanate and AITC by field pennycress seedmeal, erucin (4-methylthiobutyl isothiocyanate) by arugula seedmeal, 3-butenyl isothiocyanate and lesquerellin (6-methylthiohexyl isothiocyanate) by sweet alyssum seedmeal, and isopropyl isothiocyanate by money plant seedmeal. From our data it appears that both the type and concentration of glucosinolates and their hydrolysis products present in the seedmeals affect seed-emergence inhibition.

BIOFUMIGANT COMPOUNDS RELEASED BY FIELD PENNYCRESS (Thlaspi arvense) SEEDMEAL

Defatted field pennycress (Thlaspi arvense L.) seedmeal was found to completely inhibit seedling germination/emergence when added to a sandy loam soil containing wheat (Triticum aestivum L.) and arugula [Eruca vesicaria (L.) Cav. subsp. sativa (Mill.) Thell.] seeds at levels of 1.0% w/w or higher. Covering the pots with Petri dishes containing the soil-seedmeal mixture decreased germination of both species at the lowest application rate (0.5% w/w), suggesting that the some of the phytotoxins were volatile. CH2Cl2, MeOH, and water extracts of the wetted seedmeal were bioassayed against wheat and sicklepod (Senna obtusifolia (L.) H. S. Irwin & Barneby) radicle elongation. Only the CH2Cl2 extract was strongly inhibitory to both species. Fractionation of the CH2Cl2 extract yielded two major phytotoxins, identified by gas chromatography-mass spectrometry and NMR as 2-propen-1-yl (allyl) isothiocyanate (AITC) and allyl thiocyanate (ATC), which constituted 80.9 and 18.8%, respectively, of the active fraction. When seeds of wheat, arugula and sicklepod were exposed to volatilized AITC and ATC, germination of all three species was completely inhibited by both compounds at concentrations of 5 ppm or less. In field studies, where seedmeal was applied at 0.50, 1.25, and 2.50 kg/m2 and tarped with black plastic mulch, all of the treatments significantly reduced dry weight of bioassay plants compared to the tarped control, with the highest seedmeal rate decreasing dry matter to less than 10% of the control 30 d after seedmeal application. Field pennycress seedmeal appears to offer excellent potential as a biofumigant for high-value horticultural crops for both conventional and organic growers.

Biofumigation Potential of Field Pennycress (Thlaspi arvense) Seedmeal

Field pennycress (Thlaspi arvense L.) seedmeal was found to suppress seedling germination/emergence and biomass accumulation when added to a sandy loam soil containing wheat (Triticum aestivum L.), arugula [Eruca vesicaria (L.) Cav. subsp. sativa (Mill.) Thell.] and sicklepod (Senna obtusifolia (L.) H.S. Irwin & Barneby) seeds. Covering the pots with petri dishes containing the soil-seedmeal mixture increased phytotoxicity at the lowest application rate, suggesting that the some of the phytotoxins were volatile. Dichloromethane, methanol and water extracts of the wetted seedmeal were bioassayed against wheat and sicklepod radicle elongation. Only the dichloromethane extract was found to be strongly inhibitory to both species. Fractionation of the dichloromethane extract identified two major phytotoxins, identified by GC-MS and NMR analyses as 2-propen-1-yl (allyl) isothiocyanate (AITC) and allyl thiocyanate (ATC), which constituted 80.9 and 18.8%, respectively, of the active fraction. When seeds of wheat, arugula and sicklepod were exposed to volatilized AITC and ATC, the germination of all three species were completely inhibited by both compounds at concentrations of 5 ppm or less.

Glucosinolate breakdown products as insect fumigants and their effect on carbon dioxide emission of insects

BackgroundGlucosinolate breakdown products are volatile, therefore good candidates for insect fumigants. However, although they are insecticidal, the mode of action of such natural products is not clear. We studied the insecticidal effect of these compounds as fumigants, and monitored the production of carbon dioxide by the insects as a probe to the understanding of their mode of action.ResultsThe fumigation 24-h LC50 against the house fly (Musca domestica L.) of allyl thiocyanate, allyl isothiocyanate, allyl cyanide, and l-cyano-2-hydroxy-3-butene was 0.1, 0.13, 3.66, and 6.2 μg cm-3, respectively; they were 0.55, 1.57, 2.8, and > 19.60 μg cm-3, respectively, against the lesser grain borer (Rhyzopertha dominica Fabricius). The fumigation toxicity of some of the glucosinolate products was very close to or better than that of the commercial insect fumigants such as chloropicrin (LC50: 0.08 and 1.3 μg cm-3 against M. domestica and R. dominica, respectively) and dichlorovos (LC50: < 0.02 and 0.29 μg cm-3 against M. domestica and R. dominica, respectively) in our laboratory tests. Significantly increased CO2 expiration was found in insects exposed to the vapor of allyl isothiocyanate, allyl thiocyanate and allyl isocyanate. Allyl isothiocyanate was also found to increase the CO2 expiration of the American cockroach (Periplaneta americana L.).ConclusionsGlucosinolate breakdown products have potential as biodegradable and safe insect fumigants. They may act on the insect respiratory system in their mode of action.

Determination of isothiocyanates and related compounds in mustard extract and horseradish extract used as natural food additives

Amounts of isothiocyanates and related compounds in a mustard extract and a horseradish extract for food additive use were determined by GC, after confirmation of the identity of GC peaks by GC/MS. Amounts of allyl isothiocyanate, which included that of allyl thiocyanate, because most of the allyl thiocyanate detected in the sample was assumed to have been formed from allyl isothiocyanate during GC analysis, were 97.6% and 85.4%, in the mustard extract and the horseradish extract, respectively. Total amounts of the identified isothiocyanates in the mustard extract and the horseradish extract were 98.5% and 95.4%, respectively. Allyl cyanide, a degradation product of allyl isothiocyanate, was found in the mustard extract and the horseradish extract at the levels of 0.57% and 1.73%, respectively. beta-Phenylethyl cyanide, a possible degradation product of beta-phenylethyl isothiocyanate, and allyl sulfides were found in the horseradish extract, at the levels of 0.13% and 0.46%, respectively. Allylamine, which is another degradation product of allyl isothiocyanate, was determined after acetylation, and was found in the mustard extract and the horseradish extract at the levels of 8 micrograms/g and 67 micrograms/g, respectively.

Antimicrobial Properties of Sinigrin and its Hydrolysis Products

ABSTRACTSinigrin, a thioglucoside of Cruciferae plants, may be enzymatically hydrolyzed to yield up to four distinct aglycones when the plants are injured or mechanically disrupted. These aglycones, allyl isothiocyanate (AITC), allyl cyanide (AC), 1‐cyano‐2,3‐epithiopropane (CETP), and allyl thiocyanate (ATC), were tested for their minimum inhibitory concentration (MIC) in broth to 9 species of bacteria and 8 species of yeasts. Sinigrin, AC, and CETP at 1,000 ppm were not inhibitory to any of the bacteria or yeasts tested. The inhibitory activity of ATC was uncertain due to its gradual conversion to AITC. AITC had an MIC of 50 to 1,000 ppm for bacteria and 1 to 4 ppm for nonxerotolerant yeasts, and, against xerotolerant yeasts at 50 ppm, it retarded but did not prevent growth.

Thermal Degradation of Allyl Isothiocyanate in Aqueous Solution.

Allyl isothiocyanate in an aqueous solution was heated and refluxed at 100 degrees C for 1 h. The reaction mixtures were then extracted with methylene chloride and analyzed using gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The mixtures in aqueous phase were analyzed by high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) equipped with an atmospheric-pressure chemical ionization (APCI) interface. The compounds identified in the methylene chloride extracts included diallyl sulfide, diallyl disulfide, diallyl trisulfide, diallyl tetrasulfide, allyl thiocyanate, 3H-1,2-dithiolene, 2-vinyl-4H-1,3-dithiin, 4H-1,2,3-trithiin, and 5-methyl-1,2,3,4-tetrathiane. N,N'-Diallylthiourea, which was the major degradation product in the aqueous phase from the thermal reaction of allyl isothiocyanate, was identified by using LC-MS (APCI+), direct-probe EI-MS, and (1)H-NMR. The possible mechanism for the formation of these products was proposed.

Decomposition Products of Allyl Isothiocyanate in Aqueous Solutions

Solutions containing 1000 mg kg-1 of allyl isothiocyanate (AITC) in buffers of pH 4, 6, and 8 were stored at 80 °C and analyzed for the content of AITC, its isomerization product allyl thiocyanate (ATC), and 9 other decomposition products. The major reaction products in alkaline buffers were allylamine (AA), allyl dithiocarbamate (ADTC), diallylthiourea (DATU), and carbon disulfide (CDS). CDS and AA also arose as the major products in buffers of pH 6 and 4. Newly identified decomposition products of AITC were ADTC, diallylurea (DAU), and diallyl sulfide (DAS). Mechanisms explaining the decomposition of AITC are presented and discussed. Keywords: Allyl isothiocyanate; degradation products; allyl thiocyanate; allylamine; diallylthiourea; diallylurea; allyl dithiocarbamate; allyl allyldithiocarbamate; allyl mercaptan; diallyl sulfide; diallyl disulfide; carbon disulfide; HPLC; GLC

Experimental and theoretical studies on the isomerization of allyl thiocyanate to allyl isothiocyanate

The mechanism of isomerization of allyl thiocyanate to allyl isothiocyanate has been investigated both experimentally and theoretically. The kinetic study indicates that the reaction is unimolecular and is not ionic. The entropy of activation suggests strongly that the mechanism involves a cyclic transition state. The rate of reaction was retarded to a small extent in polar solvents relative to that in nonpolar solvents. Ab initio MO calculations indicate, in agreement with the experimental results, that the reaction proceeds through a cyclic transition state, one in which the SCN moiety is almost linear. Thus, this is a [3,3] sigmatropic rearrangement. The charge separation in the transition state was substantial. The retardation of the reaction in polar solvents was attributed to the difference in solvation in the original state and in the transition state. © 1997 John Wiley & Sons, Inc.

Experimental and theoretical studies on the isomerization of allyl thiocyanate to allyl isothiocyanate

Experimental and theoretical studies on the isomerization of allyl thiocyanate to allyl isothiocyanate

Allyl thiocyanate — Natural product or artifact in Crucifer extracts?

Allyl thiocyanate and isothiocyanate were synthesized and could be analysed by gas chromatography without isomerization by keeping the injector at, or below, 50°C. Synthetic allyl isothiocyanate contained none of the isomeric thiocyanate but allyl thiocyanate contained 0.5% of isothiocyanate. The NMR spectra indicated both compounds to be free of the corresponding isomer. Analysis of extracts of stinkweed, mustard and horseradish by GC using non-isomerizing conditions showed that only the stinkweed extract contained allyl thiocyanate. Mustard and horseradish extracts contained allyl, and other, isothiocyanates but no allyl thiocyanate. Allyl thiocyanate previously reported in extracts of mustard and horseradish was most likely an artifact caused by partial isomerization of allyl isothiocyanate under the conditions of isolation and/or analysis.

Stability of allylthiocyanate and allylisothiocyanate in bovine ruminal fluid

The rate of allylisothiocyanate (AITC) disappearance in bovine rumen fluid in vitro was 50-fold greater than the rate for allylthiocyanate (ATC). The results indicate that unlike AITC, ATC is more likely to be absorbed from the forestomachs and possibly transferred to milk.

Autolysis of Thlaspi arvense in bovine rumen fluid

The formation of allylthiocyanate (ATC) in bovine rumen fluid requires the presence of the hydrolytic plant enzyme from Thlaspi arvense. Sinigrin, alone, was not hydrolysed in vitro but allylisothiocyanate was formed in the presence of erogenous myrosinase. The ATC potential of T. arvense is described.

Volatiles in distillates of fresh, dehydrated and freeze dried horseradish

The steam-volatile constituents of locally grown horseradish (Armoracia lapathifolia, Gilib.) have been studied by gas chromatography (G.C.) and combined gas chromatography — mass spectrometry (GC-MS). Of the ten components idendified overall, six were isothiocyanates, two were nitriles, one was allyl thiocyanate and one was carbon disulfide. The distribution and concentration of flavor components in crowns, primary and secondary roots and rootlets differed from those in tops. The primary and secondary roots and crowns accounted for the bulk of the weight of the root fraction as well as its essence content. Based on allyl isothiocyanate content, the quality of horseradish essence deteriorated as the distillation time was extended. Freeze drying and dehydration of sliced roots improved the recovery and quality of the essence. Some aspects of knowledge of the formation and decomposition of selected volatiles have been discussed as the basis of interpretation of the above findings.

Volatile constituents of horseradish roots

AbstractEssences of the volatile components of five samples of horseradish root, three fresh and two of dried flakes, have been prepared and examined by gas chromatography (g.c.) and combined gas chromatography‐mass spectrometry (g.c.‐m.s.). At least 17 compounds are involved. Five of these have been rigorously identified by comparison with authentic compounds, synthesised where necessary, through mass spectra and retention data and the identities of three others have been tentatively established. The compounds concerned are methyl, ethyl, isopropyl, 2‐butyl, allyl, 4‐pentenyl and 2‐phenethyl isothiocyanate and allyl thiocyanate. The constituents of the five essences were assessed semi‐quantitatively by g.c. and definite differences found. These were reinforced by examination of the headspace vapours over the coarsely grated root.Additional attention was devoted to the allyl isothiocyanate‐thiocyanate interconversion and to the odour assessment of the volatile horseradish components.

The preparation and isomerization of allyl thiocyanate. An organic chemistry experiment

The present experiment has been devised to focus attention on two displacement reactions, one at carbon and one at sulfur and the facile allylic rearrangement of allyl thiocyanate (III) to allyl isothiocyanate (IV) which occurs during the distillation. Equations are shown in the article.