The results are consistent with a scenario in which HSA becomes acylated due to a nucleophilic attack by Tyr-411 on the substrate and then is deacylated by general acid or base catalysis with the participation of water.
Polyethylene glycol (PEG)-linked manganese halogenated
porphyrins (Chart ) catalyzed oxidation of
azo dyes (Chart ) by H2O2 under mild
conditions such as pH 8.0 at 25 °C especially when imidazole
was
present, causing the decoloration of azo dyes. The decoloration of
azo dyes by synthetic manganese porphyrins
under mild conditions was first reported. The decoloration rate
depended on the structures of the porphyrins,
in which the largest rate was observed in the presence of PEG−MnDCPP.
The decoloration may be
contributed by radical species rather than electrophilic species,
consistent with the side-chain oxidation
of toluene. Kinetics on polyethylene glycol-linked manganese
porphyrin-catalyzed decoloration of C.I.
Acid Orange 7 by hydrogen peroxide revealed that the decoloration
was contributed at the oxidation
process by manganese porphyrins with hydrogen peroxide in the polymer
domain rather than the complex-formation process between manganese porphyrins and azo
dyes.
The effects of three cyclodextrins (alpha-, beta-, gamma-CyD) on the acid hydrolysis of digoxin were examined. From the high performance liquid chromatographic tracing of each of the four components (digoxin, bisdigitoxoside, monodigitoxoside, digoxigenin) in reaction mixtures, the individual rate constants (K1-K6) were determined by analogue computer simulation. The hydrolysis was suppressed by CyDs in the order of beta-great than gamma-greater than alpha-greater than-CyD, where beta-CyD inhibited the appearance rates of digoxigenin (k3, K5, and K6) significantly. In the dissolution study of digoxin tablets, the increase in dissolution rate and decrease in acid hydrolysis were attained by inclusion complexation. The data are presented suggesting that CyDs are useful for improving the oral bioavailability of digoxin.
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