Syntheses and anti-inflammatory activities of O-acyloximes. II.

Novel O-acyloximes having an acetyl group or N-protected amino acid as an O-acyl group were synthesized by reaction with acetyl chloride or by a mixed anhydride method. 4'-Morpholinoacetophenone oxime (oxime-2) was determined to be the (E) isomer by X-ray crystal structure analysis. The anti-inflammatory activities of the test compounds were assessed in terms of the inhibitory effect on increased vascular permeability induced by histamine, and several compounds were assessed together by means of the carrageenan-induced paw edema assay. In general, acetyl oximes and tert-butyloxycarbonylphenylalanyl oximes showed inhibitory action on increased vascular permeability. Particularly important for the appearance of anti-inflammatory activity was direct attachment of the acetyl group to the oxime. Of the two isoforms of cyclooxygenase (COX-1 and COX-2), COX-1 activity was inhibited by oxime-2 and 4'-piperidinoacetophenone oxime (oxime-3) with IC50 values of 50 and 130 microM, respectively, while COX-2 activity was not inhibited. The in vitro inhibitory effect of oxime-2 and oxime-3 on COX-1 activity decreased with O-acylation of the oximes.

Effects of the ester moiety on stereoselective hydrolysis of several propranolol prodrugs in rat tissues.

The stereochemical characteristics of the hydrolysis of several ester-type prodrugs of propranolol, O-acetyl, O-propionyl, O-butyryl, O-pivaloyl and succinyl esters, were studied in phosphate buffer (pH 7.4), rat plasma and rat tissue homogenates. In phosphate buffer, no differences were observed in the hydrolysis rate between the esters of (R)- and (S)-propranolol. The effects of the ester moieties on the hydrolysis rate in phosphate buffer were in the following order: acetate > propionate > butyrate > succinate > pivalate. In rat plasma and tissue homogenates, the hydrolysis of the esters was accelerated, and stereoselective hydrolysis was observed. In plasma, the hydrolysis of the (R)-isomer was faster than that of the (S)-isomer except for the succinate ester. On the other hand, in the liver and intestine homogenates, the (S)-isomer was hydrolyzed faster than the (R)-isomer except for the succinate and pivalate esters in the liver homogenate. Also, the ratio of the hydrolysis rates (S/R) changed with the type of prodrug. As the length of the alkyl chain of the ester increased, the S/R ratio approached unity in liver and intestine homogenates but stayed almost constant in plasma. For the pivalate ester, stereoselective hydrolysis was observed in plasma and intestine homogenate but not in liver homogenate. The stereoselective hydrolysis of the succinate ester was observed only in intestine homogenate, but the S/R ratio was almost 1 in plasma, liver and intestine homogenates. No interconversion between (R)- and (S)-isomer was observed during the hydrolysis of any of the ester prodrugs. These results indicate that hydrolysis of ester-type prodrugs of propranolol occurs stereoselectively in rat tissues, and that its selectivity is dependent on the kind of tissue and prodrug.

Percutaneous permeation of basic compounds through shed snake skin as a model membrane.

Relationships between the in-vitro permeability of basic compounds through shed snake skin as a suitable model membrane for human stratum corneum and their physiochemical properties were investigated. Compounds with low pKa values were selected to compare the permeabilities of non-ionized forms of the compounds. Steady-state penetration was achieved immediately without a lag time for all compounds. Flux rate and permeability coefficient were calculated from the steady-state penetration data and relationships between these parameters and the physicochemical properties were investigated. The results showed that permeability may be controlled by the lipophilicity and the molecular size of the compounds. Equations were developed to predict the permeability from the molecular weights and the partition coefficients of basic compounds.

Syntheses and anti-inflammatory activity of novel oximes and O-acyloximes.

Novel oximes were prepared from the corresponding aldehyde or ketone in the usual way, and a number of oxime esters, O-lauroyl, O-2-pyridinecarbonyl, O-nicotinoyl, and O-isonicotinoyl oximes were synthesized by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDCI)-4-dimethylaminopyridine (DMAP) method or a mixed anhydride method, in our search for potent anti-inflammatory compounds. The anti-inflammatory activity of these compounds was assessed by the carrageenan-induced paw edema assay in rats. The oximes (4, 5, and 13), O-lauroyloxime 1L, O-nicotinoyloximes (1N, 2N, 3N, and 4N), O-isonicotinoyloxime 1I, and O-2-pyridinecarbonyloxime 7P showed higher anti-inflammatory potency than aspirin, a prostaglandin cyclooxygenase inhibitor.

Purification and reconstitution of mu-opioid receptors in liposome.

Opioid receptors solubilized from rat brain membranes with digitonin were partially purified with a newly prepared affinity resin, AF-Amino Toyopearl, coupled with a mu-antagonist Tyr-Pro-Tyr-Tyr at the C-terminus of the peptide. The purified materials were reconstituted with an inhibitory GTP-binding protein (Gi) in liposome. From displacement analyses, two binding states, with a high and a low affinities for the mu-agonist [D-Ala2,Me-Phe4,Gly-ol5]enkephalin, were observed in the reconstituted system with Gi, only a low-affinity state was observed in the reconstituted system without Gi. The results suggested that the purified materials contained the mu-opioid receptors and could functionally couple with Gi as observed in the cell membranes.

Stereoselective hydrolysis of O-acetyl propranolol as prodrug in rat tissue homogenates.

The stereochemical characteristics of the hydrolysis of O-acetyl propranolol were studied using phosphate buffer (pH 7.4), rat plasma, and rat tissue homogenates. In the phosphate buffer, no difference was observed in the hydrolysis rate between the esters of (R)- and (S)-propranolol. In rat plasma and tissue homogenates, hydrolysis of the ester was both accelerated and stereoselective. Hydrolysis of O-acetyl (R)-propranolol was five times faster than that of the (S)-isomer in rat plasma. However, in the liver and intestine homogenates, the (S)-isomer was hydrolyzed faster than the (R)-isomer. Interconversion between the (R)- and (S)-isomers was not observed under the experimental conditions. The same stereoselective hydrolysis was also observed with racemic O-acetyl propranolol. However, observed rate constants for the hydrolysis were lower than those for the pure isomers. These results indicate that enzymatic hydrolysis of O-acetyl propranolol occurred stereoselectively and the selectivity of the plasma enzyme was different from those of liver and intestine enzymes.

In vitro percutaneous transport of sodium diclofenac and diclofenac from oleaginous vehicle.

The penetration enhancement of sodium diclofenac and diclofenac by alcohols with various alkyl chains (C8 to C14) was evaluated by the steady state flux of diclofenac through rat abdominal skin. Decanol showed the greatest effect in this series. A more remarkable enhancing effect of the alcohols was observed in sodium diclofenac than in diclofenac. Diclofenac can penetrate through the ethylene-vinyl acetate membrane as a lipoid model membrane, but sodium diclofenac can not. Decanol enhanced the penetration of phenol red being dependent on its concentration in the vehicle. Therefore, decanol may interact with lipoid components of the skin and increase the aqueous pathway in the skin. These results indicate that sodium diclofenac and diclofenac may be penetrated through partially different pathways.

In vitro transport of sodium diclofenac across rat abdominal skin: effect of selection of oleaginous component and the addition of alcohols to the vehicle.

The in vitro percutaneous transport of sodium diclofenac from various oil vehicles was examined using rat abdominal skin as a model skin membrane. The overall transport of diclofenac through the skin from the oleaginous vehicles was very poor because of a poor solubility of sodium diclofenac in nonpolar oils. To increase the solubility and the permeability of sodium diclofenac, ethanol and n-octanol were added to each oil (designated as the formulated vehicles). The addition of ethanol and n-octanol to the nonpolar vehicles resulted in an extreme increase in drug solubility in each vehicle, with a remarkable increase in the permeation of diclofenac. The effects of oil components in the formulated vehicle on the permeation of diclofenac across the skin were in the following order: squalane greater than or equal to squalene greater than liquid paraffin greater than middle chain triglyceride greater than olive oil greater than castor oil. In order to clarify the reason for the differences in permeation of diclofenac from these formulated vehicles, the release of diclofenac and n-octanol from these vehicles in vitro was studied. The release rates of n-octanol from the formulated vehicles were in the following order: liquid paraffin greater than squalene greater than or equal to squalane greater than middle chain triglyceride greater than or equal to olive oil greater than castor oil. On the other hand, a linear correlation was observed between the initial release rate of diclofenac from the formulated vehicle and the in vitro permeation of diclofenac through the vehicle to the skin.(ABSTRACT TRUNCATED AT 250 WORDS)

Stereoselective hydrolysis of O-acetyl propranolol as prodrug in human serum.

A direct high-performance liquid chromatographic method was developed for the assays of the enantiomers of O-acetyl propranolol. Using this procedure, the stereochemical characteristics on hydrolysis of racemic O-acetyl propranolol as a prodrug have been studied in phosphate buffer (pH 7.4) and in 90% human serum. In the phosphate buffer, no difference in the hydrolysis rate between the esters of (R)- and (S)-propranolol was observed. In 90% human serum, the hydrolysis of the esters was accelerated, and the hydrolysis rate of the ester of (R)-isomer was about three times faster than that of the ester of (S)-isomer. The interconversion between (R)- and (S)-isomer was not observed during the hydrolysis of prodrug in buffer and in human serum. These results indicated that hydrolysis of O-acetyl propranolol occurs stereoselectively in human serum.

High-performance liquid chromatographic determination of ampicillin and its metabolites in rat plasma, bile and urine by post-column degradation with sodium hypochlorite.

A high-performance liquid chromatographic method has been developed for the determination of ampicillin (1) and its metabolites [(5R,6R)-ampicilloic acid (2), the (5S,6R)-epimer (3) and the corresponding (2R)-piperazine-2',5'-dione (4)] in rat plasma, bile and urine. The method involves the separation of 1-4 from the background components of the biological fluids on a reversed-phase C18 column, using sodium heptanesulphonate as an ion-pairing agent and methanol in the mobile phase, followed by post-column degradation with 1.5 M sodium hydroxide-0.02% sodium hypochlorite solution at ambient temperature, and detection of the degradation product(s) of each compound at 270 nm. The detection limits were about 25 ng for each compound at a signal-to-noise ratio of 3. At concentrations of 2-5 micrograms/ml of each compound, the within- and between-run precisions (relative standard deviation) were 0.77-7.15% and 1.76-5.96%, respectively. The plasma, biliary and urinary levels of 1 and its metabolites were determined by the proposed method after intravenous administration of 1 to rats.