De Novo Asymmetric Synthesis of a 6-O-Methyl-D-glycero-L-gluco-heptopyranose-Derived Thioglycoside for the Preparation of Campylobacter jejuni NCTC11168 Capsular Polysaccharide Fragments.

An enantioselective de novo synthesis of a thioglycoside derivative of the 6-O-methyl-D-glycero-L-gluco-heptopyranose residue found in the Campylobacter jejuni NCTC11168 (HS:2) capsular polysaccharide is reported. The compound is obtained from a furfural-derived chiral diol in 11 steps. Notably, compared to the only previous synthesis of this molecule, this approach significantly reduces the number of purification steps required to obtain the target.

In(III) triflate-mediated solvent-free synthesis and activation of thioglycosides by ball milling and structural analysis of long chain alkyl thioglycosides by TEM and quantum chemical methods.

Conventional solution-phase synthesis of thioglycosides from glycosyl acetates and thiols in the presence of In(III) triflate as reported for benzyl thioglucoside failed when applied to the synthesis of phenolic and alkyl thioglycosides. But, it was achieved in high efficiency and diastereospecificity with ease by solvent-free grinding in a ball mill. The acetates in turn were also obtained by the homogenization of free sugars with stoichiometric amounts of acetic anhydride and catalytic In(OTf)3 in the mill as neat products. Per-O-benzylated thioglycosides on grinding with an acceptor sugar in the presence of In(OTf)3 yield the corresponding O-glycosides efficiently. The latter in the case of a difficult secondary alcohol was nearly exclusive (>98%) in 1,2-cis-selectivity. In contrast, the conventional methods for this purpose require use of a coreagent such as NIS along with the Lewis acid to help generate the electrophilic species that actually is responsible for the activation of the thioglycoside donor in situ. The distinctly different self-assembling features of the peracetylated octadecyl 1-thio-α- and ß-D-galactopyranosides observed by TEM could be rationalized by molecular modeling.

5-Methylthiopentose: a new substituent on lipoarabinomannan in Mycobacterium tuberculosis.

We have identified and characterised in several strains of Mycobacterium tuberculosis a new 5-methylthiopentose substituent on lipoarabinomannan (LAM). The 5-methylthiopentose was initially observed in heteronuclear (1)H-(13)C-NMR spectra of intact, (13)C-enriched LAM. Oligosaccharides carrying this substituent were released from (13)C-enriched LAM and from unlabelled LAM using an endo-arabinanase from Cellulomonas gellida. The presence of the methylthio group in these oligosaccharides was established using NMR, high-resolution Fourier-transform ion cyclotron resonance mass spectrometry and tandem mass spectrometry using a Q-TOF mass spectrometer. The 5-methylthiopentose is linked to a terminal mannose in the cap structures of these oligosaccharides as evidenced by tandem mass spectrometry and by NMR. We suggest interference with the signal transduction mechanisms of infected macrophages as a possible function for this newly discovered LAM substituent.

Nutritional evaluation of low-glucosinolate rapeseed meals obtained by various processes.

Defatted meals were prepared from two new varieties of rapeseed, the 'high-glucosinolate' variety, Brassica napus, Lesira, and the 'low-glucosinolate' variety, Brassica napus, Erglu, by each of the following processes: (1) defatting of the ground seed with hexane; (2) extraction of the myrosinase-deactivated ground seed with 70% aqueous acetone for the removal of glucosinolates followed by defatting with pure acetone, and (3) autolysis of the ground seed for the decomposition of glucosinolates followed by defatting and simultaneous removal of the decomposition products with hexane. The defatted meals obtained after extraction with aqueous acetone of autolysis contain very little glucosinolates and their degradation products as compared to those obtained by defatting with hexane only. The contents of available lysine and of phytates in the meals are, to some extent, affected by the treatment for the removal of glucosinolates. The rapeseed meals were fed at different levels to protein-depleted chicks and weanling rats. The animals fed low-glucosinolate meals prepared both from high-glucosinolate and low-glucosinolate varieties of rapeseed gave superior performance with regard to the feed conversion and protein efficiency ratio as compared to the animals fed the corresponding meals which were obtained simply by defatting the seeds with hexane. The levels of thyroxine (T4) and triiodothyronine (T3) in the serum of rats fed low-glucosinolate meals indicated normal function of the thyroid, whereas those in rats fed high-glucosinolate meals revealed hypothyroidism of the animals.

Differential induction of mixed-function oxidase (MFO) activity in rat liver and intestine by diets containing processed cabbage: correlation with cabbage levels of glucosinolates and glucosinolate hydrolysis products.

Both white and Savoy-type cabbage added to a semi-purified diet at 25% dry weight and fed to rats ad lib. for 5 days significantly induced ethoxyresorufin (ERR) deethylation in the small and large intestine. Savoy cabbage also induced hepatic activity and, in general, exhibited a greater inducing effect than white cabbage. These enzyme-inducing effects were altered when the cabbage had been processed. The content of intact glucosinolate was greater in Savoy than in white cabbage. The indole glucosinolate (glucobrassicin) content of both types of cabbage was approximately halved by cooking but was unaffected by fermentation, whilst homogenization of Savoy cabbage led to the total disappearance of intact glucosinolates. Levels of the indole glucosinolate breakdown products ascorbigen and indole-3-carbinol were highest in homogenized cabbage, and ascorbigen levels were also higher in cooked than in fresh cabbage of either type. When added to the semi-purified diet and fed ad lib. to rats for 5 days, indole-3-carbinol was a potent inducer of hepatic ERR deethylation and cytochrome P-450 activity, but had much less effect in the intestine. Other glucobrassicin metabolites, diindolylmethane and indole-3-acetonitrile, also had some inducing effect in the liver but no effect in the intestine, while ascorbigen significantly induced ERR deethylation in the small and large intestine but had no effect on hepatic MFO activity.

Chemical and biological properties of indole glucosinolates (glucobrassicins): a review.

Glucosinolates are a group of secondary products commonly, but not exclusively, found in plants of the family Cruciferae. They give rise, upon enzymic hydrolysis, to a range of volatile, pungent and physiologically active compounds. Recently, particular attention has been focused upon those that are trytophan-derived--the indole glucosinolates (glucobrassicins). When chemically or enzymically hydrolysed these compounds give rise to a range of involatile indole compounds which have been implicated in the anti-carcinogenic and mixed-function-oxidase stimulatory activities of brassica vegetables. This review details the chemical and physiological properties of indole glucosinolates and their products and suggests possible areas for future research.

Formation of mutagenic N-nitroso compounds in vegetable extracts upon nitrite treatment: a comparison with the glucosinolate content.

More than 30 vegetables were screened for their potential to form biologically active N-nitroso compounds upon treatment with nitrite under acidic conditions. The total N-nitroso content was determined in the nitrite-treated and untreated extracts of the vegetables according to a modified method of Walters et al. (Analyst, Lond. 1978, 103, 1127). All treated extracts contained N-nitroso compounds at levels ranging from 23 to 789 nmol/25 mg dry matter. In the same samples the mutagenic activity was determined using the Salmonella typhimurium assay. About half of the vegetables were found to be mutagenic upon nitrite treatment. (Nitrite-treated extracts were considered to be mutagenic if the number of induced revertants was at least twice as high as that induced by the corresponding untreated extract). The content of different glucosinolates in the dry matter of the vegetables was also determined. Glucosinolates could be detected only in cruciferous vegetables, at levels ranging from 1.8 to 26.0 mumol/g dry matter. Although the nitrite-treated extracts of brassica species contained more N-nitroso compounds and induced more revertants than did other vegetables, there was no significant correlation between these parameters. However, the amounts of N-nitroso compounds formed upon nitrite treatment (expressed per fresh weight) did correlate significantly (P less than 0.01) with the amounts of glucosinolates (r = 0.95). When the glucosinolates were divided into aryl/alkyl- and indolyl-glucosinolates, the significant correlation was maintained for both subgroups (r = 0.93 and 0.95, respectively). From this it can be concluded that glucosinolates are probably involved in the formation of N-nitroso compounds in certain nitrite-treated vegetables.

Rapeseed meal glucosinolates: metabolism and effect on performance in laying hens.

Two experiments were conducted with Hyline Leghorn hens to study the metabolism and detrimental effects of rapeseed meal (RSM) glucosinolates. Raw Target RSM was force fed to 12 hens which were killed after varying time intervals (15 min., 30 min., 60 min.) and the contents of areas of the digestive tract (crop; proventriculus and gizzard; duodenum and ileum) were analyzed for the presence of hydrolysis products of progoitrin. Nitrile compounds were found to be present in all areas of the digestive tract in much larger relative amounts than was oxazolidinethione. When commercially prepared RSMs of varying glucosinolate content were fed to laying hens at a 50% level of dietary inclusion, high glucosinolate-content RSM depressed egg production (P less than 0.05) more than low glucosinolate-content RSM but did not cause a greater frequency of liver hemorrhage. Histological examination of liver tissues from hens suffering liver hemorrhage revealed a severe reticulolysis.

Glucosinolates and derived products in cruciferous vegetables: total glucosinolates by retention on anion exchange resin and enzymatic hydrolysis to measure released glucose.

Details are given for determining total glucosinolates in Cruciferae plants by a procedure measuring released glucose. The glucosinolates are separated from about 90% of other material in the plant extract by adsorption on an anion exchange resin. Then, by a selective thioglucosidase hydrolysis of the glucosinolates retained on the exchange resin, the glucose and aglucons are separated from other substances retained by the resin. Glucose is released into an aqueous medium and is equivalent to the total glucosinolates. The aglucons formed by the hydrolysis are extracted into methylene chloride and determined by gas-liquid chromatography. Based on 29 determinations of the glucose from sinigrin, analyzed under different conditions, accuracy of the total glucosinolate determination was 94.8 +/- 7.3%. The coefficient of variation, determined by duplicate analyses on extracts from 58 cabbage samples, was 4.6%.

A polarographic method for the simultaneous determination of total glucosinolates and free glucose of cruciferous material.

A rapid method for the simultaneous analysis of total free glucose and total glucosinolates in aqueous extracts of cruciferous material is described. The technique, which appears suitable for plant-breeding programs as it allows the processing of more than 100 samples per day, involves the polarographic determination of O2 uptake of free glucose by a system of double-coupled enzymes, such as myrosinase-glucose oxidase. The method has advantages over current methods, because it is very rapid (4 min per analysis), allows two determinations for each analysis, and appears to be very reproducible, accurate, and sensitive.

[Isothiocyanate and vinyl thio-oxazolidone contents of rape seeds and rape seed oil]. / Uber den Gehalt an Isothiocyanaten und Vinylthiooxazolidon in Rapssaat und Rapsöl

Comparative studies on the isothiocyanate content of rape-seeds and rape-seed oil show that, apart from nearly 300 mg/100 g of vinyl thio-oxazolidone, rape-seeds contain almost 200--300 mg/100 g of isothiocyanates of which 3-butenyl isothiocyanate and 4-pentenyl isothiocyanate (ratio of 4:1) are the main components as evidenced thin-layer and gaschromatographically. Only about 1 mg/100 g of isothiocyanates are found in pressed rape-seed oil; and but circa 10 mg/100 g, in extracted rape-seed oil. 3-Butenyl isothiocyanate and 4-pentenyl isothiocyanate (ratio of 4:1) are once more the main components. Thioglycerides are not detected in the oil. Vinyl thio-oxazolidone is found only in extracted rape-seed oil (about 2 mg/100 g).