Variation in Enzymatic Degradation Products from Major Thioglucosides in Crambe abyssinica and Brassica napus Seed Meals

VanEtten, C. H.; Daxenbichler, M. E.; Peters, J. E.; Tookey, H. L.

doi:10.1021/jf60146a027

Cited by 62 publications

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References 2 publications

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“…Experiments 3 and 4 show that a heat treatment, sufficient to inactivate the myrosinase (see Table II), does not destroy the isothiocyanate or the oxazolidinethione 'factors'. This is important in view of the results by Van Etten et al 15 concerning the lability of the factor responsible for low yield of oxazolidinethione in crambe meals, in which heat inactivation of the oxazolidinethione factor was obtained at temperatures below myrosinase inactivation when defatted meals were treated.…”

Section: Fig 1 Enzymatic Hydrolysis Of Thioglucosides At Phmentioning

confidence: 97%

Method for quantitative determination of isothiocyanates and oxazolidinethiones in digests of seed meals of rape and turnip rape

1967

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A method has been developed for the quantiitative determination of isothiocyanates and oxazolidinethiones in enzymic digests of seed meals of rape (Br,issica napus) and turnip rape (B. campestris). Good precision has been obtained; relative standard deviation was *2% when the method was applied with macro-(1 g) as well as on micro-amounts (10 mg) of seed meal.In order to obtain optimum yields from the same digests, the seed and meal were treated with hot air and hot buffer solution, respectively. The time,'temperature/moisture relationship of seed treatment necessary to inactivate the myrosinase in rape seed is presented.The results obtained with this method demonstrate that the content of progoitrin in rape seed is considerably higher than that obtained by application of an earlier widely used method, e.g. 4.8 % in defatted seed meal of Matador winter rape, compared with an earlier figure of 3 . 1 %.Introduction Defatted meals of rape and similar cruciferous seed crops have a high protein content and a reasonably well balanced amino acid composition? However the large amounts of thioglucosides present, which yield isothiocyanates and oxazolidinethiones upon enzymatic hydrolysis, limit their use as feed. Plant breeding projects to obtain varieties with the lowest possible content of such compounds have been initiated.2 With Wetter's method39 for the assay of these products of hydrolysis, problems in reproducing the results on oxazolidinethione content in a given seed sample on different occalsions were experienced. Several authors have reported a broad pH optimum at 7 for the action of myrosinase on purified thiogluc0sides5.~ whereas Wetter found a pH optimum at 4 for isothiocyanate formation in the presence of rapeseed meals. Preliminary experiments showed a higher rate of isothiocyanate release from a seed meal slurry at pH 4 than at 7 whereas in aqueous solutions of methanol extracts of the same meal the rate was higher at pH 7 than at pH 4. Thus, it was considered essential that studies on the conditions for the release of isothiocyanates and oxazolidinethione from the parent thioglucosides should be undertaken. Furthermore, a less time-consuming method, adaptable to micro-quantities was desired. The results of these studies are presented in the present paper. A preliminary report covering the principles of this new method has been published elsewhere.7Structure of thioglucosides and various split products in rape and turnip rape seeds Through degradation of two natural thioglucosides, sinigrin and sinalbin,8 and total synthesis of another naturally occurring thioglucoside, glucotropaeolin,g Ettlinger & Lundeen provided conclusive evidence for the thioglucoside structure depicted in Fig. 1. The major thioglucosides in rape and turnip rape are gluconapin and p r~g o i t r i n .~ For gluconapin the R in Fig. 1 corresponds to CH2 = CH -CH2 -CHz -; for progoitrin it is CH2 = CH-CH(OH)-CHZ-. FIG. 1. Enzymatic hydrolysis of thioglucosides at pH 7Hydrolysis of pure thioglucosides at neutral pH by an enzyme preparat...

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Section: Fig 1 Enzymatic Hydrolysis Of Thioglucosides At Phmentioning

confidence: 97%

Method for quantitative determination of isothiocyanates and oxazolidinethiones in digests of seed meals of rape and turnip rape

1967

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“…Calcd. for C5H9NOS : C,45.8;H,6.9;N,10.7;S,24.4. Found: C,45.8;H,6.9;N,10.6;S, Equal amounts (19.5 mg) of (5')-and (R)-3-hydroxypent-4-enethionamide were dissolved separately in ether (1 ml).…”

Section: (S)-3-hydroxype1zt-4-enethionarnide (4)mentioning

confidence: 99%

Enantiomeric 3-hydroxypent-4-enethionamides from thioglucosides of Crambe and Brassica seeds by action of ferrous salts

Austin¹,

Gent²,

Wolff³

1968

Can. J. Chem.

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epi-Progoitrin, the major thioglucoside of Crambe abyssinica seed, is cleaved by ferrous salts to yield (9-I-cyano-2-hydroxy-3-butene and (S)-3-hydroxypent-4-enethionamide. The products are the same whether obtained from the purified thioglucoside or from the seed meal. Identical behavior was observed for seed meal of Brassica napus, which gave corresponding derivatives of the opposite configuration. Optical rotatory dispersion and proton magnetic resonance studies suggest the existence of solvent-dependent differences in rotamer composition for the 3-hydroxypent-4-enethionamides.Canadian Journal of Chemistry, 46, 1507Chemistry, 46, (1968 Earlier publications from this laboratory have detailed the chemistry of epi-progoitrin, the major thioglucoside in seed meal of Crambe abyssinica Hochst ex R. E. Fries and of its enzymic conversion products (1-3). The enzymic reaction may lead to two distinct types of products. One, 5-vinyl-oxazolidinethione or (R)-goitrin, is formed by spontaneous cyclization of an intermediate P-hydroxy isothiocyanate (4); the other consists of open-chain nitriles derived from the aglucon of epi-progoitrin. Three of this group have been recognized: (S)-1-cyano-2-hydroxy-3-butene and a diastereoisomeric pair of episulfides related to this unsaturated nitrile.Several species of Brassica contain a thioglucoside with a similar structure to that found in Crambe. The two thioglucosides differ only in configuration about the asymmetric carbon atom in the aglucon portion of the molecule (I). The configurations persist without racemization during enzymic conversion, so that two series of enantiomorphic compounds result, depending on the source material (1, 2). A scheme showing these relationships, together with the absolute configurational assignments, was recently given (5).The occurrence of enantiomers of a compound in related plant families is unusual but not unique for Crambe and Brassica. The situation with respect to the thioglucosides of these species has been discussed by Daxenbichler et al. (1) who also cited other substances, mainly terpenes, which occur in nature as enantiomers. Analogous observations were noted for an alkaloid (20) and for the butanol derivative, betuligenol (21).Although enzymic transformation of the thioglucosides present in members of the Cruciferae and in a limited number of other plant families frequently proceeds via the isothiocyanate pathway, the route leading to nitriles may occur almost exclusively or the two types of products can be formed concurrently. Schwimmer (6) noted that the decomposition of sinigrin by myrosinase (thioglucosidase, EC3.2.3.1) in the presence of ascorbate and protein yielded nitrile at pH 3.0 but isothiocyanate at higher pH values. Further studies of this system by Ettlinger et al. (7) supported pH dependence of the observed ratio of nitrile to isothiocyanate produced. The results were explained in terms of the nonenzymatic breakdown of a labile intermediate whose rate was determined by pH. The intermediate was identified as the sinig...

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“…2 Other hydrolysis products, for example nitriles, have also been found. 3 Studies of glucosinolate content in seed of rape and turnip rape as affected by variety and environment were made by Josefsson & Appelqvist. 4 By fertiliser experiments in plastic boxes (containers), they showed that low applications of sulphate fertiliser resulted in a low content of glucosinolates in the seed, although the protein production approached normal quantities.…”

Section: Introductionmentioning

confidence: 99%

Glucosinolate content and amino acid composition of rapeseed (Brassica napus) meal as affected by sulphur and nitrogen nutrition

Josefsson

1970

J Sci Food Agric

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Rapeseed plants have been grown in soil-free culture with varying amounts of nitrogen fertiliser applied as nitrate, and with 50% of the nitrate-N exchanged for ammonium. The experiment was performed at two levels of sulphate fertiliser. Yield, protein content, glucosinolate content and amino acid composition were studied. The glucosinolate content was lower and the protein content was higher at a high level of nitrogen fertiliser. Exchange of 50% of the nitrate-N for ammonium caused no significant change in glucosinolate or protein content. The amount of glucosinolate was higher at the high sulphate level. There were no sulphur-nitrogen interactions. Content of total aspartic acid increased with nitrogen fertilisation, while total content of other amino acids did not change significantly with fertilisation.The effect of a wide variety of applications of sulphate fertiliser on glucosinolate and total amino acid content have been studied in a separate experiment. Although both protein content and methionine content were reduced at a low sulphate level, glucosinolate content was reduced considerably more.Experiments in the field revealed that although a reduction in glucosinolate content of rapeseed may be obtained from using fertilisers low in sulphur on sandy soils this does not seem possible on heavy soils. IntroductionSeed meals of rape (Brassica napus L.) and turnip rape (Brassica campestris L.) contain W 5 % protein in the dry matter with a well balanced amino acid composition.l According to Miller et aZ.1 the limiting amino acids from a nutritional point of view are isoleucine and methionine. Since methionine very often is limiting in proteins of vegetable origin, it is important to obtain as high a content of this amino acid as possible. A factor that is still more limiting for the use of these meals, however, is the content of glucosinolates. These substances can be hydrolysed by the enzymic system myrosinase, yielding sulphate, glucose and isothiocyanates, the last-mentioned compound and its secondary products being toxic to animals, causing for example goitre in non-ruminants.2 Other hydrolysis products, for example nitriles, have also been found.3 Studies of glucosinolate content in seed of rape and turnip rape as affected by variety and environment were made by Josefsson & Appelqvist.4 By fertiliser experiments in plastic boxes (containers), they showed that low applications of sulphate fertiliser resulted in a low content of glucosinolates in the seed, although the protein production approached normal quantities. Fields with light soils where the sulphur fertilisation had been kept on a low level gave samples with a glucosinolate content that was significantly lower than in samples from other fields.4In the studies of Josefsson & Appelqvist, no significant variation in glucosinolate content was found between different levels of nitrogen fertiliser. Trzebny5 found, however, in a study of field-grown material that a high level of nitrogen fertiliser caused a significantly lowered glucosinolate content. ...

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Variation in Enzymatic Degradation Products from Major Thioglucosides in Crambe abyssinica and Brassica napus Seed Meals

Cited by 62 publications

References 2 publications

Method for quantitative determination of isothiocyanates and oxazolidinethiones in digests of seed meals of rape and turnip rape

Method for quantitative determination of isothiocyanates and oxazolidinethiones in digests of seed meals of rape and turnip rape

Enantiomeric 3-hydroxypent-4-enethionamides from thioglucosides of Crambe and Brassica seeds by action of ferrous salts

Glucosinolate content and amino acid composition of rapeseed (Brassica napus) meal as affected by sulphur and nitrogen nutrition

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