Barbiturate/barbituric acid assay

More sensitive, and most frequently used, is the periodic acid-thio-barbituric acid assay devised by Warren22 and modified by Amin-off.107 122 In a reaction sequence initiated by periodate oxidation, the... 

Fusion of a barbituric acid motif and a pyrone ring afforded compounds containing a novel pyranopyrimidine core (L) that were discovered as GPR109A agonists [92,93]. This core appears to be distinct from other fused bicyclic cores such as xanthine and anthranilide based on their poor overlap. Furthermore, several compounds, exemplified by 39 and 40, provided remarkable potency in the cAMP assay. The critical acidic functional group is present as the N-PI of barbituric acid motif which has a calculated pKa of 8 [82]. 

The uses of constant-current coulometry for the determination of drugs in biological fluids are few, basically due to sensitivity restriction. Monforte and Purdy [46] have reported an assay for two allylic barbituric acid derivatives, sodium seconal and sodium sandoptal, with electrogenerated bromine as the titrant and biamperometry for endpoint detection. Quantitative bromination required an excess of bromine hence back titration with standard arsenite was performed. The assay required the formation of a protein-free filtrate of serum with tungstic acid, extraction into chloroform, and sample cleanup by back extraction, followed by coulometric titration with electrogenerated bromine. The protein precipitation step resulted in losses of compound due to coprecipitation. The recoveries of sodium seconal and sodium sandoptal carried through the serum assay were approximately 81 and 88%, respectively. Samples in the concentration range 7.5-50 pg/mL serum were analyzed by this procedure. 

Subsequently, Purdie and coworkers studied the CD induced in phencyclidine (and its pyrrolidine and morpholine analogues), 6-phenethylamine, phenobarbital, meperidine HC1, diazepam, and dilantin by 6-cyclodextrin [59], In this work, a method was described for the assay of meperidine in commercially available Demerol tablets. The complexation between 6-cyclodextrin and eight 5,5-disubstituted derivatives of barbituric acid was characterized on the basis of the... 

The color intensity of the complex (Figure 3.10.4) is much smaller than the color intensity of complex (Figure 3.10.3), so in most assays based on the Parri methodology, an amine is added. Other structures of the complexes have been suggested, for example one in which one of the carbonyl groups adjacent to the nitrogen in the barbituric acid ring coordinates to the cobalt ion. 

Vitamin A inhibited doxorubicin-induced membrane lipid peroxidation in rat tissue in vivo (CiAC-cio et al. 1993). Brain and heart membrane preparations from rats receiving vitamin A, assayed in vitro in the presence of a Fe " ascorbate induction system, showed a delay in the beginning of the lipid peroxidation and generated lesser amounts of thio-barbituric acid reactive substances, with respect in membranes from control rats. 

Thiobarbituric acid (HjTBA) just like its oxa analog, barbituric acid (HjBA), has an important role in biological and medicinal chemistry. Owing to its reactivity with carbonyl compounds (aldehydes/ketones) HgTBA is widely used to determine the extent of the autoxidative spoilage of fats and oils, commonly known as TEA assay [113]. 

Non-aqueous titration of acidic groups is carried out in pharmacopoeial assays of barbiturates, uracils and sulphonamides. 

The barbiturates have come under a great deal of study and some of our observations may be of interest. The standard method of assay for these pharmaceuticals has been and still is gravimetric. There is no doubt that this is the worst possible procedure that could be imagined for these products. Barbiturates readily undergo degradation to substances which possess no therapeutic efficacy, yet by the gravimetric method all decomposition products are included in the assay as though they were the barbiturate (decomposition products of phenobarbital are—monoureide of phenethyl malonic acid phen-... 

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