[Separation and preparation of indole alkaloids in Lycorma delicatula White. by HPLC]

A HPLC method for separating and preparing indole alkaloids is described. HPLC conditions for analysis: BIO-RAD series 700 HPLC, model 700 data station, UV: model 1749 UV-VIS monitor, column: BIO-RAD Hi-pore RP318, 250 mm x 10 mm, mobile phase: 80% methanol-H2O(gradient), flow rate: 1.5 ml/min, detection wavelength: 254 nm. On the basis of spectral (1HNMR, 13CNMR, H-H COSY, MS, DEPT) and chemical evidence, the structures of two compounds were elucidated as beta-yohimbine (yohimban-16-carboxylic acid-17-hydroxy methylester (3 alpha, 16 alpha, 17 beta)) and ajmalicine (oxayohimban-16-carboxylic acid-16,17-didehydro-19-ethyl methyl ester (19 alpha)).

Structure-activity relationships of (E)-3-(1,4-benzoquinonyl)-2-[(3-pyridyl)-alkyl]-2-propenoic acid derivatives that inhibit both 5-lipoxygenase and thromboxane A2 synthetase

As part of our research for the development of novel antiinflammatory drug candidates, we have designed and synthesized a series of (E)-3-(1,4-benzoquinonyl)-2-[(3-pyridyl)alkyl]-2-propenoic acid derivatives as dual inhibitors of 5-lipoxygenase (5-LO) and thromboxane (TX) A2 synthetase. In order to increase the absorption after oral administration, we introduced a carboxylic acid moiety into the 1,4-benzoquinone skeleton, which has 5-LO-inhibitory character. Introduction of a 3-pyridylalkyl group at the double bond of the 1,4-benzoquinonyl propenoic acid moiety afforded good to moderate inhibitory activities against the production of leukotriene (LT) B4 and TXA2 while not significantly inhibiting that of prostaglandin E2 by glycogen-induced peritoneal cells of rat (in vitro). The length of the methylene chain of the 3-pyridylalkyl group influenced the inhibition of LTB4 and TXB2 production. An increase of lipophilicity by introducing a more lipophilic alkoxy group did not markedly increase the inhibitory activity on LTB4 production. The position of alkoxy group on the 1,4-benzoquinone skeleton played an important role in TXA2 synthetase inhibition. Compounds such as 20c (E6700) with an appropriate alkoxy group and proper length of methylene side chain, together with a polar substituent (carboxylic acid), showed good inhibition of both 5-LO and TXA2 synthetase and possess a variety of pharmacologically beneficial effects.

Effects of extracts from Populus tremula L., solidago virgaurea L. and Fraxinus excelsior L. on various myeloperoxidase systems

Extracts from Populus tremula, Solidago virgaurea and Fraxinus excelsior are used as anti-inflammatory drugs. The effects of these extracts on myeloperoxidase (MPO), an enzyme liberated by activated granulocytes and known to produce the destructive agent hypochloric acid, were investigated. Populus and Fraxinus inhibited this enzyme, Solidago was without effect. These results were obtained concordantly with four different MPO-assays (H2O2/MPO; X/XOD/MPO; activated PMN; and elastase/alpha 1-PI-MPO). Fractionation of Populus and Fraxinus extracts showed that this inhibition is due to several different compounds. Well known or wide spread substances as e.g. rutin, salicylic acid, chlorogenic acid etc. had no or only little effect on the enzyme.

Novel approach for determination of correlation between in vivo and in vitro dissolution using the optimization technique

A new approach to determination of good correlations between in vivo and in vitro dissolution was studied using the optimization technique. Ibuprofen, which exhibits dissolution rate-limiting absorption, was used as a model drug. Ibuprofen capsules of two different release types were prepared, and their in vivo dissolution profiles were obtained from measurements of plasma concentration following oral administration of the capsules to beagle dogs by the mathematical deconvolution method using solution data of oral administration as a weight function. For the dissolution test to correspond to the in vivo dissolution profiles, the test was carried out at 12 levels (9 different sets of conditions) and results were analyzed with the optimization technique to deal with two factors. The first-order rate constant (kappa d) and the dissolution time at 50% (t50%) of the in vivo dissolution were selected for use as the response variables. Regression analysis was performed to describe the in vitro dissolution characteristics as functions of the pH of dissolution medium and paddle rotation speed in the paddle method. The in vivo/in vitro correlation obtained from the kappa d was better than that obtained from the t50%. The optimum conditions for dissolution testing corresponding to the in vivo kappa d were determined to be a pH 6.6 for the dissolution medium and a 56 rpm paddle rotation rate. The experimental data obtained by dissolution testing was well fit by the predicted curve derived from in vivo and in vitro dissolution profiles. This dissolution test is applicable to the formulations containing ibuprofen of particle size within the experimental range.

Degradation of antiflammin 2 under acidic conditions

Antiflammin 2 (HDMNKVLDL, AF2) is a synthetic peptide derived from the region of highest sequence similarity of lipocortin I and uteroglobin, and is a potent antiinflammatory agent without any known side effects of corticosteroids. The antiinflammatory activity of AF2 has been demonstrated, but is not reproducible between laboratories. It has been suggested that the chemical instability of this peptide is responsible for the loss of activity. The degradation of AF2 in aqueous solutions at a pH range of 3 to 10 has been reported. In this study, the degradation of AF2 at acidic pHs was monitored by reversed-phase HPLC. The reactions were studied as functions of buffer concentration and temperature. The rates of loss of AF2 followed apparent pseudo-first-order kinetics. Several products were isolated and identified by fast atom bombardment mass spectroscopy and tandem mass spectroscopy, and were the result of C- and N-terminus hydrolyses of aspartyl peptide bonds in AF2. The peptide bonds at C-termini of the aspartyl residues were most susceptible to hydrolysis, resulting in the formation of major degradation products, HDMNKVLD, MNKVLDL, and MNKVLD. The minor products from the N-terminus hydrolysis were HDMNKVL and MNKVL and formed at much slower rates.

A polysaccharide fraction of Zizyphi fructus in augmenting natural killer activity by oral administration

Shosaiko-to (Xiao-chai-hu-tang, SHO), a Kampo medicine, was prepared by decocting a prescription of 7 kinds of crude drugs, namely Bupleuri Radix, Pinelliae Tuber, Scutellariae Radix, Zizyphi Fructus, Ginseng Radix, Glycyrrhizae Radix and Zingiberis Rhizoma. Previously, we reported that the effect of the orally administered SHO in augmenting natural killer (NK) activity in the peripheral blood was attributed to the acidic polysaccharide fraction. To characterize the active components in the crude materials in SHO, the effects of extracts and various fractions were investigated by oral administration. The extracts of Zizyphi Fructus, Zingiberis Rhizoma, Scutellariae Radix, Glycyrrhizae Radix and Pinelliae Tuber augmented NK activity by oral administration. The high weight molecular fraction of Zizyphi Fructus was the most effective in augmenting NK activity. Thus, we obtained an active polysaccharide fraction from the high weight molecular fraction of Zizyphi Fructus. This polysaccharide fraction with a high molecular weight of approximately 43,000 contained 54.7% carbohydrate, 61.8% uronic acid and 20.9% protein. The sugar moiety was composed of rhamnose, arabinose, xylose, fucose, mannose, galactose, glucose and galacturonic acid in molar ratios of 28:59:11:9:7:32:20:100.

Biodegradable injectable implant systems for long term drug delivery using poly (lactic-co-glycolic) acid copolymers

Poly (lactide-co-glycolide) (PLG), is one of the most widely employed biodegradable synthetic polymers for sustained-release preparations. In the present work, PLG (50:50) copolymer has been used to deliver diclofenac sodium in the form of microspheres and in situ gel-forming systems, both of which can be injected subcutaneously. The pharmacodynamic and pharmacokinetic studies in the adjuvant-induced arthritic rats showed that the microspheres offered steady therapeutic levels of the drug in the plasma for about 16 days following a single subcutaneous injection. However, the in situ gel-forming system provided a significantly higher maximum plasma concentration and increased inhibition of inflammation, maintained for about 10 days. Injectable microspheres and in situ gel-forming implant systems of PLG (50:50) copolymer may therefore be considered as prospective implantable controlled-release dosage forms to deliver drugs in long-term therapy of chronic ailments.

Indomethacin loaded chitosan microspheres. Correlation between the erosion process and release kinetics

The preparation of chitosan microspheres covalently linked with citric acid and loaded with indomethacin is described. The release kinetics correlated with the concentration of chitosan in the microsphere preparative mixture and the pH of the release medium. Deviations from Fickian to zero order kinetics were observed at higher concentrations of chitosan and at pH 7.4. The variations induced by these parameters on drug diffusion and solubility in the matrix undergoing erosion were analyzed.

Rapid screening for acidic non-steroidal anti-inflammatory drugs in urine by gas chromatography-mass spectrometry in the selected-ion monitoring mode

A rapid screening procedure is described for the simultaneous determination of various acidic non-steroidal anti-inflammatory drugs (NSAIDs) at sub-nanogram levels. The procedure involves solid-phase extraction (SPE) of NSAIDs using Chromosorb P as the adsorbent in partition mode, with subsequent single-step conversion to tert-butyldimethylsilyl (TBDMS) derivatives, followed by direct analysis by gas chromatography-mass spectrometry (GC-MS). The characteristic [M-57]+ high-mass ions constituting the base peaks in the electron-impact mass spectra of most TBDMS derivatives permitted sensitive detection of NSAIDs by GC-MS in selected-ion monitoring (SIM) mode, even in the presence of higher levels of coextracted urinary organic acids. The detection limit for SIM of each drug was in the range 0.03-0.9 pg. When applied to urine samples (250 microliters) spiked with NSAIDs, the present GC-SIM-MS method allowed simultaneous screening for various NSAIDs with good overall precision and accuracy in the range of 10-40 ng.

Determination of fenbufen and its metabolites in serum by reversed-phase high-performance liquid chromatography using solid-phase extraction and on-line post-column ultraviolet irradiation and fluorescence detection

An improved analytical method for the detection and quantification of fenbufen and its two major metabolites is described. The assay consists of reversed-phase high-performance liquid chromatography and post-column irradiation with ultraviolet light and fluorescence detection. A highly selective chromatography separation was established on a cyanopropyl column at ambient temperature with a flow-rate of 0.5 ml/min. The analytes of interest were isolated from serum using a Bond-Elut CIN column with high recovery and selectivity. The fluorescence response of all three analytes upon UV irradiation was investigated. The post-column UV irradiation was optimized and the effect of irradiation time on the fluorescence response was determined for all three analytes. The detection limits were 10 ng/ml for each analyte using 1 ml of serum. Linear calibration curves from 50 to 375 ng/ml for all three analytes show coefficients of determination of 0.99. Precision and accuracy of the method were within 3.9-6.5 and 5.1-7.4% for fenbufen, 3.5-6.4 and 4.9-6.3% for metabolite II (expressed as lactone III) and 5.4-7.4 and 2.6-7.4% for metabolite IV, respectively.

A single amino acid difference between cyclooxygenase-1 (COX-1) and -2 (COX-2) reverses the selectivity of COX-2 specific inhibitors

Nonsteroidal anti-inflammatory drugs (NSAIDs) currently available for clinical use inhibit both COX-1 and COX-2. This suggests that clinically useful NSAIDs inhibit pro-inflammatory prostaglandins (PGs) derived from the activity of COX-2, as well as PGs in tissues like the stomach and kidney (via COX-1). A new class of compounds has recently been developed (SC-58125) that have a high degree of selectivity for the inducible form of cyxlooxygenase (COX-2) over the constitutive form (COX-1). This unique class of compounds exhibit a time-dependent irreversible inhibition of COX-2, while reversibly inhibiting COX-1. The molecular basis of this selectivity was probed by site-directed mutagenesis of the active site of COX-2. The sequence differences in the active site were determined by amino acid replacement of the COX-2 sequences based on the known crystal structure of COX-1, which revealed a single amino acid difference in the active site (valine 509 to isoleucine) and a series of differences at the mouth of the active site. Mutants with the single amino acid substitution in the active site and a combination of three changes in the mouth of the active site were made in human COX-2, expressed in insect cells and purified. The single amino acid change of valine 509 to isoleucine confers selectivity of COX-2 inhibitors in the class of SC-58125 and others of the same class (SC-236, NS-398), while commonly used NSAIDs such as indomethacin showed no change in selectivity. Substitutions of COX-1 sequences in COX-2 at the mouth of the active site of COX-2 did not change the selectivity of SC-58125. This indicates that the single amino acid substitution of isoleucine at position 509 for a valine is sufficient to confer COX-2 selectivity in this example of a diaryl-heterocycle COX inhibitor.

Thiazolidine diones, specific ligands of the nuclear receptor retinoid Z receptor/retinoid acid receptor-related orphan receptor alpha with potent antiarthritic activity

Rat adjuvant arthritis is a chronic T cell-dependent autoimmune disease with many similarities to rheumatoid arthritis. We have identified a class of thiazolidine diones with high potency in suppressing chronic inflammation and joint destruction in this experimental model. The lead compound CGP 52608 (1-(3-allyl-4-oxothiazolidine-2-ylidene)-4-methylthiosemicarbazone) exhibits antiarthritic activity at daily oral doses between 0.01 and 1 mg/kg and was shown to specifically activate the retinoid Z receptor/retinoid acid receptor-related orphan receptor alpha (RZR/RORalpha) in low nanomolar concentrations. This receptor is a novel member of the superfamily of ligand-inducible transcription factors, and we have recently identified the pineal gland hormone melatonin as a natural ligand. Structure-activity relationship studies with 13 closely related analogues of CGP 52608 revealed a striking correlation between RZR/RORalpha activation and antiarthritic activity. We therefore suggest that nuclear signaling via RZR/RORalpha is a key mechanism in mediating the antiarthritic effects of these thiazolidine diones and may open a novel therapeutic approach for the treatment of rheumatoid arthritis and other autoimmune diseases. The existence of a nuclear melatonin receptor may lead to a better understanding of the immunomodulatory actions of melatonin.

Non-steroidal anti-inflammatory agents, Part 20. Method for testing non-steroidal anti-inflammatories: the modified hen's egg chorioallantoic membrane test (HET-CAM test) compared to other procedures

The delay of onset of irritation phenomena at the chorioallantoic membrane of incubated hen's eggs, a parameter for anti-inflammatory activity, was determined for the pharmaceutical substances diclofenac, flufenamic acid, ibuprofen, indomethacin, ketoprofen, piroxicam, phenylbutazone, salicylic acid, and sodium salicylate. Alongside questions relating to the dose-effect ratio, metabolisation, recovery, and diffusion of the substances to their site of action were investigated. The reproducibility of the procedure and its selectivity with regard to substances with a different mechanism of action is proven. The method allows classification of the substances according to their anti-inflammatory potency. However, correlation with the results of enzyme inhibition or in vivo results is only possible to a limited extent.

In-vitro evaluation of sustained release ibuprofen microspheres

Microspheres for oral use have been employed to target and to sustain the release of the drug. The objective of this study was to use the melt dispersion technique and aqueous vehicle to entrap ibuprofen into wax carrier (carnauba wax) with the aid of surfactant (Pluronic L-62). The effects of different levels of Pluronic L-62, stirring speed, and ibuprofen levels, as well as the in-vitro release rate of ibuprofen were evaluated. The in-vitro dissolution of ibuprofen in phosphate buffer pH 7.2 showed that microspheres prepared with low amount of drug (1.5 g) released 58.1% of ibuprofen after 6 hours, while microspheres prepared with high amount of drug (6.0 g) released only 38.9% of ibuprofen. Microsphere formulations prepared by using aqueous vehicle were spherical and of smooth surface. In general the melt dispersion technique was a successful method for preparing sustained release ibuprofen microspheres.

Effect of tablet integrity on the dissolution rate of sustained-release preparations

The objective of this study was to evaluate the effect of tablet integrity on the dissolution rate. The model drug used for this study was aspirin. A dissolution study was performed with three commercially-available aspirin tablets (ZORprin, Bayer 8-h aspirin and Bayer aspirin), two of which were sustained-release tablets. For ZORprin, the average dissolution data indicated that the in vitro release rate of aspirin was consistent with the intended design of the sustained-release wax matrix tablets only when the tablets were intact. The split tablets showed a consistently higher release profile over time, with a 50% higher release at 6 h. However, the Bayer 8-h aspirin and plain aspirin tablet data showed that tablet integrity had no significant impact on the dissolution rate, because the intact and split tablets showed similar drug release profiles over time. In conclusion, care should be taken to administer sustained-release tablets, avoiding any breaking or crushing of the tablets unless this is directed by the manufacturer.

Studies on selectin blockers. 2. Novel selectin blocker as potential therapeutics for inflammatory disorders

As a part of our studies of selectin blockers, we prepared 1-(2-tetradecylhexadecyl)-3'-O-sulfo Le(X) 1 and 1-(2-tetradecylhexadecyl) sLe(X) 2 and examined their inhibitory activities against natural ligand (sLe(X)) binding to E-, P-, and L-selectins. Compounds 1 and 2 were 2 times more potent than the sLe(X) tetrasaccharide toward E-selectin binding and up to 4 times more potent than sLe(X) toward P- and L-selectin binding. Interestingly, compound 1 provided dose-dependent protective effects against an immunoglobulin E-mediated skin reaction in mouse ears. This protective effect was associated with diminished tissue accumulation of neutrophils in the ear (as assessed by myeloperoxidase). These findings indicate that the modification of sLe(X) or 3'-O-sulfo Le(X) with a "branched anchor", a 2-tetradecylhexadecyl group, is useful in the design of a more potent selectin blocker, which has broad inhibitory activities toward all selectins.

Novel terphenyls as selective cyclooxygenase-2 inhibitors and orally active anti-inflammatory agents

A novel series of terphenyl methyl sulfones and sulfonamides have been shown to be highly potent and selective cyclooxygenase-2 (COX-2) inhibitors. The sulfonamide analogs 17 and 21 were found to be much more potent COX-2 inhibitors and orally active anti-inflammatory agents than the corresponding methyl sulfone analogs 16 and 20, respectively, albeit with some decrease in COX-2 selectivity. Structure-activity relationship studies have determined that incorporation of two fluorine atoms in the central phenyl group, as in 20 and 21, is extremely advantageous for both in vitro COX-2 potency and selectivity as well as in vivo activity. Several noticeable examples in the 1,2-diaryl-4,5-difluorobenzenesulfonamide series are 21a-c,k,l,n (COX-2, IC50 = 0.002-0.004 microM), in which all have in vitro COX-1/COX-2 selectivity > 1000. In addition, sulfonamides 21a,b,d,g,j,m,n,q were shown to have greatly enhanced oral activity with more than 90% inhibition of prostaglandin E2 production in the air pouch model of inflammation. Furthermore, sulfonamide 21b was found to be very active in the rat adjuvant-induced arthritis model (ED50 = 0.05 mg/kg) and carrageenan-induced hyperalgesia assay (ED50 = 38.7 mg/kg) with no indication of gastrointestinal toxicity in rats at doses as high as 200 mg/kg.

Photolabeling of prostaglandin endoperoxide H synthase-1 with 3-trifluoro-3-(m-[125I]iodophenyl)diazirine as a probe of membrane association and the cyclooxygenase active site

Previous studies of the crystal structure of the ovine prostaglandin endoperoxide H synthase-1 (PGHS-1)/S-flurbiprofen complex (Picot, D., Loll, P. J., and Garavito, R. M. (1994) Nature 367, 243-249) suggest that the enzyme is associated with membranes through a series of four amphipathic helices located between residues 70 and 117. We have used the photoactivatable, hydrophobic reagent 3-trifluoro-3-(m-[125I]iodophenyl)diazirine ([125I]TID) which partitions into membranes and other hydrophobic domains to determine which domains of microsomal PGHS-1 are subject to photolabeling. After incubation of ovine vesicular gland microsomes with [125I]TID, ovine PGHS-1 was one of the major photolabeled proteins. Proteolytic cleavage of labeled PGHS-1 at Arg277 with trypsin established that [125I]TID was incorporated into both the 33-kDa tryptic peptide containing the amino terminus and the 38-kDa tryptic peptide containing the carboxyl terminus. This pattern of photolabeling was not affected by the presence of 20 mM glutathione, indicating that the photolabeling observed for PGHS-1 was not due to the presence of [125I]TID in the aqueous phase. However, nonradioactive TID as well as two inhibitors, ibuprofen and sulindac sulfide, which bind the cyclooxygenase active site of PGHS-1, prevented the labeling of the 38-kDa carboxyl-terminal tryptic peptide. These results suggest that [125I]TID can label both the cyclooxygenase active site in the tryptic 38-kDa fragment and a membrane binding domain located in the 33-kDa fragment. Cleavage of photolabeled PGHS-1 with endoproteinase Lys-C yielded a peptide containing residues 25-166 which was labeled with [125I]TID. This peptide contains the putative membrane binding domain of ovine PGHS-1. Our results provide biochemical support for the concept developed from the crystal structure that PGHS-1 binds to membranes via four amphipathic helices located near the NH2 terminus of the protein.

Spectroscopic characterization of bendazac and benzydamine: possible photochemical modes of action

The involvement of near-UV light in cataract development suggests that potential anti-cataract drugs may display unusual spectroscopic properties. As bendazac impedes certain effects associated with lens opacification, we have characterized the singlet and triplet states of bendazac and its analog, benzydamine, by fluorescence and phosphorescence methods. These compounds have much shorter triplet state lifetimes compared to the triplet state lifetimes observed in proteins. Our results raise the possibility that the photoprotective action of these compounds may result from their ability to dissipate energy through the triplet state. We propose alternative modes for the photoprotective actions of these compounds.

Azulene derivatives as TXA2/PGH2 receptor antagonists--II. Synthesis and biological activity of 6-mono- and 6-dihydroxylated-isopropylazulenes

In order to examine the correlation between activity and hydrophilicity of the side chain of sodium 3-[4-(4-chlorobenzenesulfonylamino)butyl]-6-isopropylazulene -1-sulfonate (KT2-962), a non-prostanoid TXA2/PGH2 receptor antagonist, one or two hydroxyl groups were introduced into the isopropyl moiety. A series of 6-hydroxylated-isopropylazulenes were synthesized by regioselective oxidation of 6-isopropylazulenes and their in vitro and in vivo antagonistic activities were studied. Both the primary and tertiary alcohols, monohydroxylated derivatives, exhibited potent biological activities comparable to unmodified 6-isopropylazulenes both in vitro and in vivo. In contrast, the activities of 1,2- and 1,3-diols of 6-substituted derivatives, markedly decreased, but recovered by O-isopropylidenation of the dihydroxyl moiety. These findings indicate that the moderate hydrophobicity of substituent at the 6-position of the azulene ring might be required for the activity and the size of the substituent at this position, not so rigid for keeping potent biological activity.

[Alkaloids in the flowers of Sophora viciifolia Hance]

Six alkaloids have been isolated from the flowers of Sophora viciifolia for the first time. Based on of physico-chemical methods and spectroscopic analysis, their structures have been identified as oxymatrine, oxysophocarpine, sophocarpine, matrine, sophoramine and sophoridine.

Chemical and immunochemical comparison of protein adduct formation of four carboxylate drugs in rat liver and plasma

Carboxylate drugs usually form acyl glucuronide conjugates as major metabolites. These electrophilic metabolites are reactive, capable of undergoing hydrolysis, rearrangement, and covalent binding reactions to proteins. The last-mentioned property has the potential to initiate immune and other toxic responses in vivo. In this study, we compared the extent and pattern of covalent adduct formation in plasma and livers of rats dosed with the nonsteroidal anti-inflammatory drugs (NSAIDs) zomepirac (ZP) and diflunisal (DF), the hypolipidemic agent clofibric acid (CA), and the anti-epileptic agent valproic acid (VPA). These drugs form acyl glucuronides with diverse intrinsic reactivities (apparent first order degradation t 1/2 values of 0.5, 0.6, 3, and 60 h, respectively). Rats were dosed iv twice daily for 2 days (50 mg/kg for ZP, DF, and CA, 150 mg/kg for VPA). Chemical analysis of tissues obtained 6 h after the last dose revealed adduct concentrations of 0.31, 0.44, 0.28, and 0.05 micrograms of drug equivalents/mL of plasma and 2.21, 2.31, 0.96, and 0.96 micrograms of drug equivalents/g of liver for ZP, DF, CA and VPA treatments, respectively. For both plasma and liver, the higher concentrations of adducts were found with ZP and DF, which have the more reactive glucuronides. The low concentrations of VPA adducts found in plasma were in keeping with the very low reactivity of its glucuronide. In liver, however, VPA adducts achieved concentrations of the same order of magnitude as the other drugs and were accompanied by adducts of the (E)-2-en metabolite of VPA at 0.38 micrograms of VPA equivalents/g of liver. The liver data for VPA can be explained by an acyl CoA/beta-oxidation pathway of adduct formation in addition to that from acyl glucuronidation. Immunoblotting using rabbit polyclonal antisera raised against synthetic drug-protein adducts revealed major bands at 110, 140, and approximately 200 kDa in livers of ZP- and DF-treated rats. A fourth major band at 70 kDa in ZP-treated liver had the same apparent molecular weight as the only major band detected in CA-treated liver. A 140 kDa band was detected in liver tissue from VPA-treated rats, as well as several lower molecular weight bands. In plasma, the antisera specifically detected drug-modified serum albumin in samples from rats treated with ZP, DF, and CA, but not VPA. The results with this small series of carboxylate drugs suggested that (a) adduct concentrations in plasma but not liver could be related to acyl glucuronide reactivity, (b) while some modified proteins detected were common, the pattern of modification varied from drug to drug, and (c) caution should be exercised in attributing adduct formation exclusively to the acyl glucuronidation pathway.

hP, the component of log P controlling structure-activity relationships amongst non-steroidal anti-inflammatory drugs

A range of 25 drugs and other compounds selected from published sources by strict criteria, has been used to confirm that their ability to inhibit the production of prostaglandin by mouse peritoneal macrophage does not correlate with log P but with hP, the parameter composed of only the hydrophobic contributions (atoms and groups composed of carbon, hydrogen and halogens). Other heteroatoms and physical properties can usually be ignored. Anti-inflammatory activity does not depend upon pKa or partition phenomena unless extreme, nor does it depend primarily upon the structural types within the range phenols, salicylic acids, mefenamic acids, areneacetic and profenic acids.

Oxidative degradation of antiflammin 2

PURPOSE

To study the oxidation of the methionine residue of antiflammin 2 (HDMNKVLDL, AF2) as a function of pH, buffer concentration, ionic strength, and temperature using different concentrations of hydrogen peroxide and to determine the accessibility of methionine residue to oxidation.

METHODS

Reversed-phase high-performance liquid chromatography (RPHPLC) was used as the main analytical method in determining the oxidation rates of AF2. Calibration curves for AF2 and the oxidation product, methionine sulfoxide of AF2 (Met(O)-3-AF2), were constructed for each measurement using standard materials. Fast Atom Bombardment Mass Spectroscopy (FABMS) was used to characterize the product.

RESULTS

Met(O)-3-AF2 was the only oxidation product detected at pH 3.0 to 8.0. The oxidation rates were independent of buffer concentrations, ionic strength, and pH from 3.0 to 7.0. However, there was an acceleration of the rates at basic pHs, and small amounts of degradation products other than Met(O)-3-AF2 were observed in this alkaline region.

CONCLUSIONS

Oxidation of methionine in AF2 does not cause the biological inactivation reported by other laboratories since this drug is relatively stable under neutral conditions in the absence of oxiding agent.

l-Menthol, oleic acid and lauricidin in absorption enhancement of free and sodium salt of diclofenac using ethanol treated silicone membrane as model for skin

The mechanism of l-menthol, oleic acid and lauricidin as enhancers on percutaneous absorption was examined using diclofenac (DH) as a hydrophobic drug and sodium diclofenac (DNa) as a hydrophilic drug in in vitro diffusion experiments with two kinds of membranes: ethanol-treated and untreated silicone membranes; these were models for the lipid and pore pathways of skin. A 20% w/w ethanol-aqueous solution decreased the flux of DH but increased the flux of DNa significantly across the treated membrane compared with those fluxes across the untreated membrane, suggesting that DH penetrated by the lipid pathway and DNa by the pore pathway. The permeability of DNa through the pore pathway decreased significantly across the treated membrane with the addition of oleic acid and lauricidin. l-Menthol increased the permeability coefficients of DH and DNa more in a treated membrane than in an untreated one, showing the same tendency as in rat skin. Thus, while oleic acid and lauricidin did not increase the permeation of DNa by the pore pathway, l-menthol appeared to enhance the permeation of the drug by both the lipid and pore pathways.

Five new anthocyanins, ternatins A3, B4, B3, B2, and D2, from Clitoria ternatea flowers

Five new ternatins 1-5 have been isolated from Clitoria ternatea flowers, and the structures have been determined by chemical and spectroscopic methods as delphinidin 3-malonylG having 3'-GCG-5'-GCG, 3'-GCG-5'-GC, 3'-GCGCG-5'-GC, 3'-GCGC-5'-GCG, and 3'-GCGC-5'-GC side chains, respectively, in which G is D-glucose and C is p-coumaric acid. Pigment 1 had symmetric 3',5'-side chains. Compounds 3 and 4 are structural isomers. These ternatins were shown to form an intramolecular stacking between the aglycon ring and the 3',5'-side chains in solution.

Dibenzoxepinone hydroxylamines and hydroxamic acids: dual inhibitors of cyclooxygenase and 5-lipoxygenase with potent topical antiinflammatory activity

Hydroxylamine and hydroxamic acid derivatives of a known nonsteroidal antiinflammatory dibenzoxepine series display both cyclooxygenase (CO) and 5-lipoxygenase (5-LO) inhibitory properties. Many of these new dual CO/5-LO inhibitors also exhibit potent topical antiinflammatory activity in the arachidonic acid-induced murine ear edema model. On the basis of their promising profile of in vitro and in vivo activities, hydroxamic acids 24h, 3-(6,11-dihydro-11-oxodibenz[b,e]oxepin-2-yl)-N-hydroxy-N-++ +methylpropanamide (HP 977), and 25, 3-(6,11-dihydrodibenz[b,e]oxepin-2-yl)-N-hydroxy-N- methylpropanamide (P10294), were selected as developmental candidates for the topical treatment of inflammatory skin disorders.

Discovery of the hemifumarate and (alpha-L-alanyloxy)methyl ether as prodrugs of an antirheumatic oxindole: prodrugs for the enolic OH group

Ether, ester, and carbonate derivatives of the antirheumatic oxindole 1 were prepared and screened as potential prodrugs of 1. This effort led to the discovery of the (alpha-L-alanyloxy)-methyl ether and hemifumarate derivatives of 1 which deliver the drug efficiently into the circulation of test animals, are stable in the solid state, and possess good stability in solution at low pH as required to ensure gastric stability. Success in achieving acceptable bioavailabilities of 1 across species (rats, dogs, and monkeys) followed the inclusion of ionizable functionality within the promoiety to compensate for masking the polar enolic OH group of the free drug. However, the introduction of ionizable functionality was often associated with decreased stability, as demonstrated by the hemisuccinate, hemiadipate, hemisuberate, and alpha-amino ester derivatives of 1 which could not be isolated. A clear exception was the hemifumarate derivative of 1 which was not only isolable but actually more stable at neutral pH than the nonionizable ester analogues. The solution and solid state stability of the hemifumarate, together with its activity as a prodrug of 1, suggests that hemifumarate be considered as an alternative to hemisuccinate as a prodrug derivative for alcohols, particularly in situations where solution state stability is an issue.

Azole phenoxy hydroxyureas as selective and orally active inhibitors of 5-lipoxygenase

Azole phenoxy hydroxyureas are a new class of 5-lipoxygenase (5-LO) inhibitors. Structure-activity relationship studies have demonstrated that electronegative substituents on the 2-phenyl portion of the oxazole tail increased the ex vivo potency of these inhibitors. Similar substitutions on the thiazole analogs had only minor contribution to the ex vivo activity. The trifluoromethyl-substituted oxazole 24 was the best compound of the oxazole series in both the ex vivo (6 h pretreated rats) and in vivo (3 h pretreated rats) RPAR assay with ED50 values of approximately 1 and 3.6 mg/kg, respectively, but was weakly active in the allergic guinea pig assay. Oxazole 50 was equally active in both the RPAR and guinea pig in vivo models and was similar to zileuton. The unsubstituted thiazole 52 was the best compound of the thiazole series, by inhibiting the leukotriene B4 biosynthesis in the RPAR assay (3 h pretreated rats) by 99%, at an oral dose of 10 mg/kg, and the bronchoconstriction in the allergic guinea pig by 50%, at an intravenous dose of 10 mg/kg. Oxazole 24 demonstrated high and selective 5-LO inhibitory activity in the in vitro assays, with IC50 values ranging from 0.08 microM in mouse macrophages to 0.8 microM in human peripheral monocytes to 1.2 microM in human whole blood. This activity was selective for 5-LO, as concentrations up to 15 microM in mouse macrophages did not affect prostaglandin formation. Oxazole 59 was the most active inhibitor in the human monocyte assay with an IC50 value of 7 nM.

Detection of non-steroidal anti-inflammatory drugs in equine plasma and urine by gas chromatography-mass spectrometry

A gas chromatographic-mass spectrometric (GC-MS) procedure for the detection of seventeen non-steroidal anti-inflammatory drugs (NSAIDs) in equine plasma and urine samples is described. The extraction of the compounds from the biological matrix was performed at acidic pH (2-3) with diethyl ether. Ethereal extracts were washed with a saturated solution of sodium hydrogencarbonate (urine) or treated with a solid mixture of sodium carbonate and sodium hydrogencarbonate (plasma). The ethereal extracts were dried and derivatized by incubation at 60 degrees C with methyl iodide in acetone in the presence of solid potassium carbonate. Mono- or bismethyl derivatives of the NSAIDs were obtained. After derivatization kinetic studies, 90 min was the incubation time finally chosen for screening purposes for adequate methylation of all the compounds under study. For individual confirmation analyses, shorter incubation times can be used. The chromatographic analysis of the derivatives was accomplished by GC-MS with a run time of 13 min. In general, extraction recoveries ranged from 23.3 to 100% in plasma and from 37.5 to 83.8% in urine samples. Detection limits from less than 5 to 25 ng/ml were obtained for both plasma and urine samples using selected-ion monitoring. The procedure was applied to the screening and confirmation of NSAIDs in routine doping control of equine samples.

Diarylspiro[2.4]heptenes as orally active, highly selective cyclooxygenase-2 inhibitors: synthesis and structure-activity relationships

A novel series of 5,6-diarylspiro[2.4]hept-5-enes was shown to provide highly potent and selective cyclooxygenase-2 (COX-2) inhibitors. A study of structure-activity relationships in this series suggests that 3,4-disubstituted phenyl analogs are generally more selective than 4-substituted phenyl analogs and that replacement of the methyl sulfone group on the 6-phenyl ring with a sulfonamide moiety results in compounds with superior in vivo pharmacological properties, although with lower COX-2 selectivity. Several compounds have been shown to possess promising pharmacological properties in adjuvant-induced arthritis and edema analgesia models. The absence of gastrointestinal (GI) toxicity at 200 mpk of several selected compounds in rats and mice corresponds well with the weak potency for inhibition of COX-1 observed in the enzyme assay. Methyl sulfone 55 and sulfonamide 24 were shown to have superior in vivo pharmacological profiles, low GI toxicity, and good oral bioavailability and duration of action.

Stereoselective disposition of flurbiprofen from a mutual prodrug with a histamine H2-antagonist to reduce gastrointestinal lesions in the rat

The in vitro and in vivo stereoselective hydrolysis characteristics of the mutual prodrug FP-PPA, which is a conjugate of flurbiprofen (FP) with the histamine H2-antagonist PPA, to reduce gastrointestinal lesions induced by FP were investigated and compared with those of FP methyl ester (rac-FP-Me) and FP ethyleneglycol ester (rac-FP-EG). The rac-FP derivatives were hydrolyzed preferentially to the (+)-S-isomer in plasma and to the (-)-R-isomer in liver and small intestinal mucosa. Interestingly, in the gastric mucosa, the stereoselectivity of hydrolysis of (-)-R-FP-PPA was opposite from that of rac-FP-Me and rac-FP-EG, which suggested that the stereoselective hydrolysis of FP-PPA was helpful in reducing gastric damage induced by (+)-S-FP. However, hydrolysis of all rac-FP derivatives was found to be catalyzed by carboxylesterases in the gastric mucosa. The stereoselective disposition of FP enantiomers early after intravenous administration of rac-FP-PPA could be explained by the stereoselective formation of (-)-R-FP from rac-FP-PPA in the liver. (-)-R-FP-PPA was completely hydrolyzed to form (-)-R-FP in vivo, while 78% of (+)-S-FP-PPA was hydrolyzed to (+)-S-FP, with a corresponding decrease in the area under the curve. Twenty-five percent of (+)-S-FP-PPA might be eliminated as the intact prodrug or its metabolites other than FP. The most important bioconversion of FP-PPA occurred in plasma, and additional hydrolysis of the R-enantiomer in liver resulted in the stereoselectivity observed following both i.v. and p.o. administration.

In-vitro evaluation of biphenylyl acetic acid-beta-cyclodextrin conjugates as colon-targeting prodrugs: drug release behaviour in rat biological media

Biphenylyl acetic acid was selectively conjugated to one of the primary hydroxyl groups of beta-cyclodextrin through an ester- or amide-linkage, and the physicochemical properties (aqueous solubility and hydrolysis) were investigated. Aqueous solubility of the conjugates was lower than those of either drug or parent beta-cyclodextrin. The amide conjugate was stable in aqueous solution and in rat biological fluids and gastrointestinal contents. The ester conjugate was hydrolysed to beta-cyclodextrin and biphenylyl acetic acid at moderate rates resulting in a V-shaped rate-pH profile in aqueous solution. The ester conjugate released the drug preferentially when incubated with the contents of caecum or colon, whereas no appreciable drug release was observed on incubation with contents of stomach or intestine, nor on incubation with intestinal or liver homogenates, nor on incubation with rat blood. The present results suggest that the ester-type drug conjugate of beta-cyclodextrin may serve as a colon-targeting prodrug.

Antioxidant action of a new flavonic derivative in acute carbon tetrachloride intoxication

The antioxidant potential of a new flavonic derivative named conventionally theophylline-rutoside [TR-1722] was estimated by the measurement of G-6-Pase activity (marker enzyme for the endoplasmic reticulum), catalase activity (enzyme involved in the antioxidant defence process), and total -SH groups from the hepatic homogenate, using CCl4 as a free radical generating model. To show changes in the permeability of the hepatocyte membrane, the activity of lactate dehydrogenase (LDH) in plasma was determined. The obtained results suggest that TR-1722 acts by curtailing both lipid peroxidation and alkylation processes.

Biologically active flavonoids and terpenoids from Egletes viscosa

The steam volatile components from the hexane extract of dried flower buds of Egletes viscosa were identified by gas chromatography-mass spectrometry as trans-carvyl acetate, cis-carvyl acetate, sabinyl acetate, verbenyl acetate, cyclopentaethylidene, geranyl acetate and 5-methylfuranone, and trans-pinocarvyl acetate (major component). From the non-volatile residue, centipedic acid and a novel clerodane diterpene, 12-acetoxy-hawtriwaic acid lactone, were isolated. From the ethanol extract, ternatin (4',5-dihidroxy-3,3',7,8-tetramethoxyflavone), was isolated. Ternatin showed anti-inflammatory, hepatoprotection and gastroprotection properties, and, according to the NCI protocols, it showed moderate activity against HIV. The diterpenes showed antispasmodic activity. Structure determination of these secondary metabolites was accomplished by spectrometric methods, including 2D NMR, chemical interconversion and X-ray crystallographic analysis.

Albumin binding sites for etodolac enantiomers

Non-steroidal anti-inflammatory drugs (NSAIDs) are strongly bound to human serum albumin (HSA), mainly to sites I and II. The aim of this study was to characterize the binding site(s) of etodolac enantiomers under physiological conditions (580 microM HSA) using equilibrium dialysis. The protein binding of etodolac enantiomers, alone or in various ratios, was studied in order to evaluate the potential competition between them. Our results showed that (S)-etodolac was more strongly bound to HSA than (R)-etodolac. The displacement of one enantiomer by its antipode was observed only at high concentrations of the competitor, and was more pronounced for (S)-form. Displacement studies of the enantiomers by specific probes of sites I and II of albumin, dansylamide, and dansylsarcosine, respectively, showed that (R)-etodolac was slightly displaced by both these probes whereas the free concentration of (S)-etodolac increased markedly in the presence of dansylsarcosine. Moreover, the binding of ligands to sites I and II is usually affected by alkaline pH, by chloride ions, and by fatty acids. For etodolac, the presence of 0.1 and 1 M chloride ions and increasing pH (5.5-9) decreased the binding of both enantiomers. The same result was obtained with addition of octanoic acid. Conversely, the addition of oleic, palmitic, or stearic acid to the protein solution increased the binding of (R)-etodolac, but decreased that of its antipode. All these findings suggest (R)- and (S)-etodolac interact mainly with site II of HSA, and that the (R)-isomer is also bound to site I under physiological conditions.

No effect of albumin on the dermal absorption rate of hydrocortisone 21-butyrate, permethrin or diflunisal in the isolated, single-pass perfused rabbit ear

Rabbit ears were single-pass perfused with a buffer solution containing either 6% hetastarch or 5% bovine serum albumin. Hydrocortisone 21-butyrate (5 mM), diflunisal (17 mM) or permethrin (33 mM) was added to isopropyl myristate with 5% polyethylene, and applied to about 40% of the epithelial surface area of the ear. Hydrocortisone 21-butyrate or permethrin were not found in the effluent with hetastarch or albumin. Following cutaneous ester hydrolysis, the appearance rate of hydrocortisone was about 4 pmol/min per cm2 in the hetastarch- or the albumin-containing buffer solution. No hydrolysis of permethrin was detected; the appearance rate of 3-phenoxybenzyl alcohol with 3-phenoxybenzoic acid corresponded to the absorption rate of the substrate impurities. During ex vivo perfusion of intact skin, serum albumin in the perfusion fluid may not enhance the appearance rate of xenobiotics in the effluent following dermal application when the distribution coefficient n-octanol/water is > 2,000 or when the xenobiotic is ionized at physiological pH. In general, for all substances investigated with our perfusion model thus far, the appearance rates decreased with rising distribution coefficient (n-octanol/buffer pH 7.4). High lipophilicity hinders the release from isopropyl myristate and the penetration through the skin.

Physicochemical characterization of diclofenac N-(2-hydroxyethyl)pyrrolidine: anhydrate and dihydrate crystalline forms

This study on diclofenac N-(2-hydroxyethyl)pyrrolidine (DHEP) characterizes and compares the anhydrate (DHEPA) and dihydrate (DHEPH) solid state forms using powder X-ray diffraction, infrared spectroscopic, and thermal analyses. Heats of solution and intrinsic dissolution rates are determined. The thermodynamics of hydration are discussed and the entropic cost of dihydrate formation is calculated. Reported differences in the solution behavior of DHEP crystallized from different solvents are explained. The molecular structures of both solid forms were determined and are presented. Crystal data for DHEPA: triclinic, space group P-1 (No 2), a = 11.662(2) A, b = 11.874(2) A, c = 15.296(3) A, alpha = 76.183(14) degrees, beta = 84.575(12) degrees, gamma = 87.028(12) degrees V = 2046.8(6)A3, Z = 4. Crystal data for DHEPH: triclinic, space group P-1 (No 2), a = 9.356(3) A, b = 9.920(2) A, c = 13.5413(12) A, alpha = 69.915(12) degrees, beta = 82.05(2) degrees, gamma = 71.51(2) degrees, V = 1118.9(4) A3, Z = 2. The experimentally observed ease of dehydration under conditions of nitrogen purge is explained in terms of crystal packing within the dihydrate.

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.

The reaction of ebselen with peroxynitrite

Ebselen, 2-phenyl-1,2-benzisoselenazol-3(2H)-one, rapidly reacts with peroxynitrite, the rate constant being of the order of 10(6) M-1 s-1; the reaction yields the selenoxide of the parent molecule, 2-phenyl-1,2-benzisoselenazol-3(2H)-one 1-oxide, as the sole selenium-containing product; a stoichiometry of 1 mol of ebselen reacted and of the selenoxide formed per mole of peroxynitrite was observed. The reaction was studied in detail at neutral and alkaline pH (pH 10-11). It also proceeds at acidic pH where peroxynitrous acid (ONOOH) is predominant, the yield of the selenoxide being lower because peroxynitrous acid (pKa = 6.8) decays rapidly. Reduction of the selenoxide in cells to regenerate ebselen would allow for a sustained defense against peroxynitrite. This novel reaction constitutes a potential cellular defense line against peroxynitrite, one of the important reactive species in inflammatory processes.

Preclinical and clinical development of dexketoprofen

Dexketoprofen trometamol is a water-soluble salt of the dextrorotatory enantiomer of the nonsteroidal anti-inflammatory drug (NSAID) ketoprofen. Racemic ketoprofen is used as an analgesic and an anti-inflammatory agent, and is one of the most potent in vitro inhibitors of prostaglandin synthesis. This effect is due to the S(+)-enantiomer (dexketoprofen), while the R(-)-enantiomer is devoid of such activity. The pharmacokinetic profile of ketoprofen and its enantiomers was assessed in several animals species and in human volunteers. In humans, the relative bioavailability of oral dexketoprofen trometamol (12.5 and 25 mg, respectively) is similar to that of oral racemic ketoprofen (25 and 50 mg, respectively), as measured in all cases by the area under the concentration-time curve values for S(+)-ketoprofen. Dexketoprofen trometamol, given as a tablet, is rapidly absorbed, with a time to maximum plasma concentration (tmax) of between 0.25 and 0.75 hours, whereas the tmax for the S-enantiomer after the racemic drug, administered as tablets or capsules prepared with the free acid, is between 0.5 and 3 hours. Peak plasma concentrations of 1.4 and 3.1 mg/L are reached after administration of dexketoprofen trometamol 12.5 and 25 mg, respectively. From 70 to 80% of the administered dose is recovered in the urine during the first 12 hours, mainly as the acyl-glucuronoconjugated parent drug. No R(-)-ketoprofen is found in the urine after administration of dexketoprofen [S(+)-ketoprofen], confirming the absence of bioinversion of the S(+)-enantiomer in humans. in animal studies, the anti-inflammatory potency of dexketoprofen was always equivalent to that demonstrated by twice the dose of ketoprofen. Similarly, animal studies showed a high analgesic potency for dexketoprofen trometamol. The R(-)-enantiomer demonstrated a much lower potency, its analgesic action being apparent only in conditions where the metabolic bioinversion to the S(+)-enantiomer was significant. The gastric ulcerogenic effect of dexketoprofen at various oral doses (1.5 to 6 mg/kg) in the rat do not differ from those of the corresponding double doses (3 to 12 mg/kg) of racemic ketoprofen. Repeated (5-day) oral administration of dexketoprofen as the trometamol salt causes less gastric ulceration than was observed after the acid form of both dexketoprofen and the racemate. In addition, single dose dexketoprofen as the free acid at 10 to 20 mg/kg does not show a significant intestinal ulcerogenic effect in rats, while racemic ketoprofen 20 or 40 mg/kg is clearly ulcerogenic to the small intestine. The analgesic efficacy of oral dexketoprofen trometamol 10 to 20 mg is superior to that of placebo and similar to that of ibuprofen 400 mg in patients with moderate to serve pain after third molar extraction. The time to onset of pain relief appeared to be shorter in patients treated with dexketoprofen trometamol than in those treated with ibuprofen 400 mg. Dexketoprofen trometamol was well tolerated, with a reported incidence of adverse events similar to that of placebo.

Chirality and nonsteroidal anti-inflammatory drugs

The nonsteroidal anti-inflammatory drugs (NSAIDs) are of significant clinical importance and include congeners of many chemical classes, some of which incorporate an asymmetric or chiral carbon atom. With very few exceptions, chiral NSAIDs have been marketed for clinical use as racemates. However, it is apparent that differences, sometimes major, exist between enantiomers in terms of their pharmacological and toxicological properties. With regard to the ability of chiral NSAIDs to inhibit cyclo-oxygenase, their chief mechanism of action, major or exclusive activity is confined to enantiomers of the S-stereoconfiguration. Accordingly, it is questionable whether the R-antipodes should be included in the final drug product for use in clinic. In addition to differences between enantiomers in terms of their pharmacodynamic properties, pharmacokinetic differences are possible for chiral NSAID isomers, and these may modulate preexisting enantioselectivities at the site of action of such compounds. As a consequence, a considerably simpler pharmacological profile is likely to result from the use of single enantiomers versus racemic mixtures.

Rational design and synthesis of small molecule, non-oligosaccharide selectin inhibitors: (alpha-D-mannopyranosyloxy)biphenyl-substituted carboxylic acids

The calcium dependent E-selectin/sialyl Lewisx (sLex) interaction plays a key role in inflammation where it mediates the rolling of leukocytes prior to firm adhesion and extravasation from the vasculature. A model of E-selectin/sLex binding, along with previously reported structure-activity relationships of sLex-related oligosaccharide, was used in the rational design of non-oligosaccharide inhibitors of this pivotal interaction. A palladium-mediated biaryl-coupling (Suzuki) reaction was used as the key step to prepare a number of substituted biphenyls which were assayed for their ability to inhibit the binding of E-, P-, and L-selectin-IgG fusion proteins to sLex expressed on the surface of HL60 cells. Some of the compounds developed had greater in vitro potency than the parent sLex tetrasaccharide and are currently being evaluated in in vivo models of inflammation to select a candidate for clinical development.

Linear and non linear competition plots in the deoxyribose assay for determination of rate constants for reaction of nonsteroidal antiinflammatory drugs with hydroxyl radicals

Performing the deoxyribose (DR) assay for determination of the rate constants for reaction of non steroidal antiinflammatory drugs with hydroxyl radicals led to some unusual competition plots. The molecules from the arylpropionic family of drugs: ibuprofen, flurbiprofen, ketoprofen and naproxen produced the linear relationship. However, acemetacin, diclofenac Na, flufenamic acid, indometacin, indometacin, niflumic acid, tolmetin Na and sulindac presented non linear competition plots manifesting at relatively low drug concentrations. This effect was corrected by increasing DR concentrations from 2.8 mM to 15 mM. The modification did not affect rate constants values for those derivatives which already presented a linear plot at 2.8 mM, but allowed to calculate rate constants for other compounds. It is suggested that the experimental conditions have to be adapted particularly for those derivatives with a relatively high rate constant for reaction with the radical species. The oxicam derivatives (tenoxicam and piroxicam) presented another kind of deviation that revealed a prooxidant effect in this system: non linear plots were also observed at relatively low drug concentrations, but in the opposite direction than for the other molecules. This last effect was independent of DR concentration but could be corrected by increasing ascorbate concentration in the system.

Radical scavenger activity of bendazac, an anticataract non-steroidal anti-inflammatory agent

Oxidative damage to lens components is associated with cataract formation and reactive oxygen species (ROS) overproduction at inflammation sites is thought to lead to the development of inflammatory disorders. Bendazac is a non-steroidal anti-inflammatory drug able to delay the cataractogenic process. Aim of the present study is to characterize, both chemically and biologically, the activity of this anticataract agent as a radical scavenger. Bendazac has been shown to be a strong reacting substrate in a chemical oxidizing system, which mimics a physiological pathway of hydroxy radical generation. In the Fenton-Cier reaction the drug rapidly forms a mixture of hydroxylated derivatives, among which 5-hydroxybendazac, bendazac's main metabolite, being a hydroxy radical scavenger itself. Moreover, by means of a rapid and sensitive flow cytometric method able to determine reactive oxygen intermediate production, bendazac and its 5-hydroxy derivative were shown to inhibit oxidative burst activation in polymorphonuclear neutrophil leukocytes (PMNLs).

Moment analysis of stereoselective biliary excretion and chiral inversion of ketoprofen enantiomers in perfused rat liver

The stereoselective local disposition of ketoprofen was evaluated by the single-pass perfusion experiment following a bolus injection of R(-)- or S(+)-ketoprofen into the liver from the portal vein. The elution time profiles of enantiomers into the hepatic vein and the excretion time profiles into the bile were kinetically assessed by local moment analysis. The hepatic recovery ratios (FH) of both enantiomers were < 1%, and the mean hepatic transit times (tH) were approximately 7 s. After the injection of S-ketoprofen into the liver, the biliary excretion ratio (Fb) of total S-ketoprofen was 68% (15% S-ketoprofen and 53% glucuronide) and the mean biliary transit time (tb) of S-ketoprofen was 10 min. R-Ketoprofen inversion from S-ketoprofen was not observed in either the perfusate or in the bile. After the injection of R-ketoprofen, the Fb of total R-ketoprofen was 12% (3% R-ketoprofen and 9% glucuronide), and tb of R-ketoprofen was 8 min. The Fb of total S-ketoprofen inverted from R-ketoprofen was 24% (7% S-ketoprofen and 17% glucuronide), and the tb of inverted S-ketoprofen was 17 min. Forty-six percent of R-ketoprofen was inverted to S-ketoprofen during a single pass through the rat liver, and the mean inversion time was 7.5 min. It was concluded that the unidirectional chiral inversion of ketoprofen was stereospecific, and the hepatic uptake and biliary excretion were stereo-nonspecific.

The problem of racemization in the stereospecific assay and pharmacokinetic evaluation of ketorolac in human and rats

PURPOSE

A comparison of a previously reported indirect (precolumn derivatization) assay for ketorolac (KT) and a new direct method described here was made to establish the conditions under which KT may undergo racemization and to explain the observed discrepancies in the pharmacokinetics of KT reported in the literature.

METHODS

A previously reported pre-column derivatization method and a new direct method were employed to determine the effect of pH and ionic strength on racemization. Using the conditions where no racemization occurred, the pharmacokinetics in humans and rats, and protein binding of KT enantiomers were determined.

RESULTS

Under the chromatographic conditions employed for the direct assay, no racemization was observed. Under high pH and ionic strength, however, both methods resulted in KT racemization. The indirect method resulted in rapid and complete racemization due to the strong basic conditions required for derivatization. In both humans and rats, the pharmacokinetics of racemic KT were stereoselective with the R enantiomer being predominant (AUC S/R: humans, 0.26; Rats: 0.45). This is likely due to more extensive plasma protein binding of S than its antipode (unbound S/R: 1.35).

CONCLUSIONS

The discrepancies in the literature may be explained by rapid racemization of KT that occurs during sample preparation for the pre-column derivatization method. Considerations should be given to the possibility of racemization during the assay development and validation.