Single-bubble sonochemiluminescence in aqueous luminol solutions

Sonochemiluminescence (SCL) of luminol due to a single bubble is studied through spectral measurement. No SCL was observed from a stable single bubble that emitted high-intensity sonoluminescence (SL). In contrast, SCL was observed under conditions of an unstable dancing bubble, where a bubble grows and ejects tiny bubbles, making it "dance" by counteraction. Furthermore, SCL was observed from dancing bubbles even when SL was not observed, depending on the dissolved gas content. The instability of bubble collapse is the key parameter governing SCL.     

Evaluation of the disintegration time of rapidly disintegrating tablets via a novel method utilizing a CCD camera

Many kinds of rapidly disintegrating or oral disintegrating tablets (RDT) have been developed to improve the ease of tablet administration, especially for elderly and pediatric patients. In these cases, knowledge regarding disintegration behavior appears important with respect to the development of such a novel tablet. Ordinary disintegration testing, such as the Japanese Pharmacopoeia (JP) method, faces limitations with respect to the evaluation of rapid disintegration due to strong agitation. Therefore, we have developed a novel apparatus and method to determine the dissolution of the RDT. The novel device consists of a disintegrating bath and CCD camera interfaced with a personal computer equipped with motion capture and image analysis software. A newly developed RDT containing various types of binder was evaluated with this protocol. In this method, disintegration occurs in a mildly agitated medium, which allows differentiation of minor distinctions among RDTs of different formulations. Simultaneously, we were also able to detect qualitative information, i.e., morphological changes in the tablet during disintegration. This method is useful for the evaluation of the disintegration of RDT during pharmaceutical development, and also for quality control during production.     

Novel approach to arylhydrazones, the precursor for Fischer indole synthesis, via diazo esters derived from α-amino acid esters

A novel method for synthesizing arylhydrazones, the precursor for Fischer indole synthesis, using aryllithium reagents and α-diazo esters that are easily obtained from α-amino acid esters, is described.     

Studies on topical antiinflammatory agents. I. Synthesis and vasoconstrictive activity of corticosteroid 17-succinyl esters

A series of 17-succinyl derivatives of four corticosteroids was prepared. They were tested for vasoconstrictive activity in humans, using 9 alpha-fluoro-11 beta, 21-dihydroxy-16 beta-methyl-17 alpha-valeryloxy-1,4-pregnadiene-3,20-dione (betamethasone 17-valerate, BV) as a standard. The activities of the 21-chloro 17-methylsuccinate compounds (6A, 6C and 6D) were greater than that of BV. A structure-activity relationship study showed that the activities of the 21-chloro 17-methylsuccinates were more potent than those of the corresponding 21-esters.     

Photocontrol of spatial orientation and DNA cleavage activity of copper(II)-bound dipeptides linked by an azobenzene derivative

Copper(II) ion-bound CysGly dipeptides linked by an azobenzene derivative were photoisomerized between the trans and cis forms. The two copper(II) ion centers were positioned close to each other in the cis form, whereas they were far away from each other in the trans form. The copper complex in the cis form exhibited DNA cleavage activity, whereas the activity in the trans form was negligible. The DNA cleavage activity of the cis form is attributed to the cooperation of the closely located copper(II) centers. The present results show the photocontrol of the cooperation of metal ions for DNA cleavage.     

Liquid chromatographic analysis of cinchona alkaloids in beverages

A method for the determination of Cinchona extract (whose main components are the alkaloids cinchonine, cinchonidine, quinidine, and quinine) in beverages by liquid chromatography was developed. A beverage with an alcohol content of more than 10% was loaded onto an OASIS HLB solid-phase extraction cartridge, after it was adjusted to pH 10 with 28% ammonium hydroxide. Other beverages were centrifuged at 4000 rpm for 5 min, and the supernatant was loaded onto the cartridge. The cartridge was washed with water followed by 15% methanol, and the Cinchona alkaloids were eluted with methanol. The Cinchona alkaloids in the eluate were chromatographed on an L-column ODS (4.6 mm id x 150 mm) with methanol and 20 mmol/L potassium dihydrogen phosphate (3 + 7) as the mobile phase. Cinchona alkaloids were monitored with an ultraviolet (UV) detector at 230 nm, and with a fluorescence detector at 405 nm for cinchonine and cinchonidine and 450 nm for quinidine and quinine (excitation at 235 nm). The calibration curves for Cinchona alkaloids with the UV detector showed good linearity in the range of 2-400 microg/mL. The detection limit of each Cinchona alkaloid, taken to be the concentration at which the absorption spectrum could be identified, was 2 microg/mL. The recovery of Cinchona alkaloids added at a level of 100 microg/g to various kinds of beverages was 87.6-96.5%, and the coefficients of variation were less than 3.3%. A number of beverage samples, some labeled to contain bitter substances, were analyzed by the proposed method. Quinine was detected in 2 samples of carbonated beverage.     

Effect of structural change in viologen acceptors on the rate of single electron transfer from tributylphosphine

The "flexible" 3 and "rigid" cyclic viologens 4, diquarternary salts of 2,2'-bipyridine and 1,10-phenanthroline, respectively, were treated with tributylphosphine (1) in acetonitrile containing a large amount of methanol under an argon atmosphere. A single electron transfer (SET) easily occurred from the latter to the former, the SET to 4 being 10(5)-10(6) times faster than the SET to 3. The reorganization energy lambda for the latter SET is thought to be larger than that for the former SET, because 3 undergoes a structural change upon the one-electron reduction to its radical cation, whereas the one-electron reduction of 4 takes place without a structural change. Taking into account the difference in lambda, and also taking into account the bond formation energy brought about by the follow-up reaction of the phosphine radical cation 1*(+) with methanol, the observed kinetics were well interpreted in terms of the Marcus theory.