5- hydantoin prevention

The mechanism of action of hydantoins is not yet conclusive. According to one hypothesis, hydantoins prevent high-frequency activation of the epileptogenic center and also facilitate secretion of sodium ions, which reduces excitation of neurons and prevents then-activation upon contact with impulses from the epileptogenic center. 

DMDM hydantoin is used in shampoos and cosmetics to prevent molds, mildews, and bacterial spoilage. 

Two widely used preservatives, DM DM hydantoin and imidazo-lidinyl urea, are ingredients used in many shampoos to prevent fungal and bacterial spoilage. They release formaldehyde to kill germs. 

V-Subslilulion and 5,5-disubstitution prevent ring opening as demonstrated by various examples. Ethotoin (3-ethyl-5-phenylhydantoin, 4.230), in contrast to its /V-dcclhylalcd metabolite, was not detectably hydrolyzed by DHPase. No ring-opened metabolite was found for phenytoin (5,5-diphenyl-hydantoin, 4.231) or nirvanol (5-ethyl-5-phenylhydantoin, 4.232), which is the AT-demethylated metabolite of mephenytoin (4.233) [144],... 

Dantrolene, a hydantoin derivative, reduces the contraction of skeletal muscle, acting directly on the muscle and not at the neuromuscular junction. It is thought to reduce the amount of calcium released and hence prevent excitation-contraction coupling (Figure 26.4). Its usefulness in the treatment of anesthetic-induced malignant hyperthermia may be due to its calcium-related uncoupling actions. 

The presence of a substituent in the 3-position of the NCA precludes equilibrium (6) and hence prevents the occurrence of reaction (18). It follows that, on the basis of the mechanisms described above, such NCA s should not polymerize unless a protic base (for example a primary or secondary amine) or other source of protons (for example, 3-methyl hydantoin) is present. If it could be established that polymerization does proceed with an aprotic base in aprotic media then some other mechanism of polymerization must be operative. This matter has been of central importance in discussions of various mechanisms of polymerization which have been advanced (Section 3). Experimentelly, it is not easy to obtain definitive evidence because of the high sensitivity of NCA s to protonic impurities (such as water and alcohols) in the presence of bases. It has been shown [18, 19, 38a] that proline NCA (X) and sarcosine NCA (I Ri = R2 = H, R3 = CH3) do not polymerize in the presence of tertiary bases under strictly aprotic conditions. With alkoxides, realization of such conditions is difficult, but it would appear that, at least with proline NCA, such strong bases can bring about ionization of the methine hydrogen and hence initiate polymerization as shown in (26). Evidence for this mechanism is provided by the observation that while sodium methoxide enriched... 

The amino acid ester forms the hydantoin 33 with the isocyanate 41. The free amine 32 attacks the isocyanate carbon and the nucleophilic isocyanate nitrogen in 42 then reacts with the electrophilic ester moiety. The carbonate base prevents protonation of the amine. 

Sorbinil 282 is a compound of potential therapeutic interest, because it prevents or alleviates the chronic complications of diabetes mellitus, due to its ability to inhibit the enzyme aldose reductase. Sarges et al. prepared 282 and its enantiomer by the reaction sequence shown in Scheme 12.71, involving a brucine resolution of the racemic hydantoin precursor 284. " The free base of brucine forms a crystalline complex with 282, whereas the other enantiomer of 282 only forms a crystalline complex with brucine hydrochloride. Since this resolution technique does not work with certain congeners of sorbinil, a synthesis via an asymmetric induction sequence (Scheme 12.72) has also been developed that seems generically applicable to optically active spiro hydantoins. Both methodsrequired 2,3-dihydro-6-fluoro-47/-l-benzopyran-4-one 283 and the introduction of the amino acid functionality... 

Polyplastics [88] added hydantoin to PET, PTT or PBT for the purpose of reducing evolution of terephthalic acid vapour during processing, thus preventing deposits of this material building up in processing equipment. 

Two widely used preservatives, DMDM hydantoin and imidazolidinyl urea, are found in many shampoos, to prevent fungal and bacterial spoilage. They release formaldehyde to kill germs. Other broad-spectrum biocide are isothiazolinone and the related methylisothiazolinone and methylchlo-roisothiazolinone. Sodium benzoate is another preservative used in shampoos. It kills bacteria, fungi, and yeasts, and works well in acidic mixtures. 

Preservatives Shampoos present an ideal environment for microbial growth, which can have a harmful effect on the physical/chemical properties of the shampoo and may pose a health hazard to the consumer. To prevent microbial growth, preservatives are added to shampoos. Among those used are methyl and propyl parabens, DMDM hydantoin, quater-nium-15, phenoxyethanol, imidazolidinyl urea, and a mixture of methylchloroisothiazoli-none and methylisothiazolinone. The selection of preservative is determined through challenge testing, which subjects the product to the worst conditions encountered in manufacture, shelf storage, and use (14). 

The biological performance illustrated above is remarkable for its speed, spectrum and potency, and offers many advantages in applications related to the principal needs for antimicrobial activity preservation, odor control, prevention of carriage and dissemination of disease agents, and wearer protection. These features differentiate hydantoin grafted cotton from all other treatments. The efficacy reflects the power of Cl, and extends to mammalian viruses, even in the presence of high bioburden levels (data not shown). 

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