Beta-diketones: peak shape challenges and the use of mixed-mode high-performance liquid chromatography methodology to obtain fast, high resolution chromatography.

Historically, indirect methods have been used for the HPLC analysis of beta-diketone compounds because of the very poor peak shapes and resolution obtained on conventional HPLC stationary phases. In this paper we demonstrate that it is possible to obtain good peak shapes for underivatised beta-diketone compounds, in a simulated reaction mixture, using only conventional mobile phases with mixed-mode stationary phase HPLC columns. Optimum conditions were obtained using the mixed-mode reversed-phase strong anion exchange column Primesep B, supplied by SIELC Technologies, with a 0.1% aq. TFA/MeOH gradient method and a column temperature of 55 degrees C.

UK-63,052 complex, new quinomycin antibiotics from Streptomyces braegensis subsp. japonicus; taxonomy, fermentation, isolation, characterisation and antimicrobial activity.

UK-63,052 complex, a new group of quinomycin-like antibiotics comprising UK-63,052 (factor A), UK-63,598 (factor C), UK-65,662 (factor B) and several uncharacterised minor components, is produced by a new subspecies of the genus Streptomyces for which the name Streptomyces braegensis Dietz subsp. japonicus, is proposed. The strain, N617-29, is characterised by a negative melanin reaction, grey aerial mycelium, spiral spore chains and smooth or slightly warty spores. Structure determination has identified UK-63,052, C56H68N10O14S2, UK-63,598, C53H62N10O14S2 and UK-65,662, C55H66N10O14S2 as quinaldic acid substituted quinomycins with unusual bridgehead sulfur substitution as shown in Fig. 3.

On the mechanisms of kappa-opioid-induced diuresis.

In conscious saline loaded rats, the kappa-opioid agonists tifluadom, U50488, and ethylketocyclazocine, given subcutaneously, induced a characteristic diuresis which could be antagonized by naloxone. Bilateral adrenal demedullation significantly reduced adrenal gland catecholamine content and plasma adrenaline levels, but did not significantly affect plasma corticosterone levels, indicating that the adrenal cortex remained both intact and functional. Seven days following bilateral adrenal demedullation, the subcutaneous administration of the kappa-agonists no longer induced diuresis. However, demedullation did not affect the diuretic response to frusemide or clonidine, nor did it affect the antidiuretic response induced by the mu-opioid agonists morphine and buprenorphine. Adrenal catecholamines do not appear to be involved in kappa-opioid-induced diuresis, since pretreatment with propranolol, prazosin and idazoxan did not affect the diuretic response in intact animals. The results indicate a link between the adrenal medulla and kappa-opioid-induced diuresis and suggest that a peripheral mechanism may also be involved in mediating this effect.

Specificity of the opioid affinity reagent, DALECK, in a set of isolated tissue assay systems.

The C-terminal chloromethyl ketone derivative of D-Ala2-Leu5-enkephalin (DALECK) has previously been shown to act as an affinity reagent at opioid receptors. The specificity of this derivative in its reversible interaction with functional opioid receptors has been examined here in a set of four field-stimulated isolated tissue preparations; the mouse, rat and rabbit vas deferens and the guinea pig ileum. Agonist potencies relative to selective reference agonists and Schild analysis were used to elucidate the overall activity of DALECK when interacting reversibly with opiate receptors under normal physiological conditions in the isolated tissue preparations. Under these conditions the ligand shows a very strong mu-selectivity. Data obtained in the guinea pig ileum suggest that DALECK is more potent than Tyr-D-Ala-Gly-N(CH3)Phe-Gly-ol (DAGO) when acting through mu-receptors. In contrast in the mouse vas deferens DALECK is at least 70-fold less potent than the delta-ligand D-Thr2-Leu5-enkephalin-Thr (DTLET). DALECK shows little interaction with kappa-receptors.

Sodium ions increase the binding of the antagonist peptide ICI 174864 to the delta-opiate receptor.

The ability of N,N-diallyl-Tyr-Aib-Aib-Phe-Leu-OH (ICI 174864) to displace [3H]-[D-Ala2, D-Leu5]enkephalin bound to the delta-opioid site is increased 8-16 fold by addition of 25mM NaCl. A smaller shift is observed for the related N,N-diallyl-Tyr-Gly-Gly-psi-(CH2S)-Phe-Leu-OH (ICI 154129) but no significant shift is seen with either naloxone or diprenorphine. The results stress the importance of using the correct medium for binding assays, and suggest the changes in delta-receptor conformation induced by Na+ ions also increase peptide antagonist binding.

In vivo studies on delta opioid receptors.

[D-Pen2, D-Pen5]enkephalin (DPDPE), a selective agonist at delta opioid receptors, causes excessive vertical rearing when given icv to rats or s.c. to mice. Tolerance develops to this behaviour. Rats do not rear excessively when injected icv with the following prototype agonists at opioid receptors: DAGO, dynorphin A, U-50488H or SK&F 10047. The incidence of DPDPE-induced rearing is reduced when rats are pretreated s.c. with ICI 174864 (a selective antagonist at delta opioid receptors) (A50 = 0.09 mg/kg) but not by ICI 178173 (an inactive analogue of ICI 174864); this finding suggests that delta binding sites mediate the behaviour. Pretreatment with naloxone attenuates rearing but the antagonism is unimpressive over the dose range tested (0.05-1 mg/kg, s.c.). Low doses of haloperidol (A50 = 0.05 mg/kg, s.c.) antagonize the rearing. Dopamine may therefore mediate the behaviour through delta receptor modulation of dopamine release. The practical gain from this study is as follows: a simple, discriminating test is now available for evaluating novel delta agonists and antagonists in vivo.

Kappa opioid binding sites in rat spinal cord.

The spinal cord of the rat is shown to contain only a low level of kappa-binding sites, comparable to rat brain. [3H]Bremazocine appears to label an additional class of sites which do not appear to be of mu, delta, or kappa specificity.

Conversion of dynorphin-(1-9) to [Leu5]enkephalin by the mouse vas deferens in vitro.

The inhibitory action of dynorphin-(1-9) on the electrically stimulated mouse vas deferens was seen to be antagonised by the delta-selective opioid antagonist ICI 174864. The observed delta-receptor mediated responses were partially, but not totally, prevented by peptidase inhibitors which protect the C- and N-termini of dynorphin-(1-9). [3H]Dynorphin-(1-9) is rapidly degraded by slices of vasa deferentia of the mouse. The major product of this metabolism co-elutes with [Leu5]enkephalin on reverse phase HPLC. It is concluded that a major component of the inhibitory effects of dynorphin-(1-9) on the mouse vas deferens is mediated by degradation to [Leu5]enkephalin which in turn acts through delta-receptors. It is possible that in other in vitro and in vivo systems, the effects produced by dynorphin-(1-9) might be similarly mediated by delta-receptor activation.

The use of [3H]-[D-Pen2,D-Pen5]enkephalin as a highly selective ligand for the delta-binding site.

The characteristics of the binding of [3H]-[D-Pen2,D-Pen5]enkephalin were determined in homogenates of guinea-pig and rat brain. In the guinea-pig, the maximum binding capacity for [3H]-[D-Pen2,D-Pen5]enkephalin was 4.19 pmol g-1 and the KD 1.61 nM. In the rat, the corresponding values were 2.47 pmol g-1 and 5.42 nM. In both species, the maximum binding capacity and the affinity were not altered when mu-binding was suppressed with [D-Ala2,MePhe4,Gly-ol5]enkephalin. The mu-agonists, [D-Ala2,MePhe4,Gly-ol5]enkephalin and morphine, displaced a small portion of the binding of [3H]-[D-Pen2,D-Pen5]enkephalin with high affinities.

Substituted 5H-dibenz[b,g]-1,4-oxazocines and related amino acids with antiinflammatory activity.

During an investigation of the antiinflammatory properties of a number of tetracyclic derivatives of 6,8-dichlorodibenz[b,f]oxepin-10(11H)-one, the ring-expanded 1,3-dichloro-5H-dibenz[b,g]-1,4-oxazocine (9) was prepared and found to be considerable pharmacological interest. It was subsequently found that the corresponding ring-opened amino acid 66, a close analogue of the antiinflammatory agent fenclofenac, also possessed significant antiinflammatory activity, superior both to the dibenzoxazocine and to fenclofenac. These findings prompted extensive synthetic programs in both areas, and a number of derivatives in the amino acid series showed potencies considerably in excess of the standard compound. These phenylacetic acids, however, were significantly more ulcerogenic than fenclofenac whereas the corresponding dibenzoxazocines showed few signs of ulcerogenicity at doses up to 1 g/kg.

Opiate binding in the rat spinal cord: evidence for mu and delta sites.

The presence of binding sites for ligands of mu and delta, in addition to kappa selectivity, have been demonstrated in the lumbo-sacral spinal cord of the rat by direct binding of [3H]ligands. These findings have been confirmed by competition studies. This information helps explain the observed pharmacology of opioids after intrathecal administration.

Opiate receptors in the rat vas deferens.

The nature of the opiate receptor population in the rat vas deferens (RVD) has been examined by evaluating the interaction of a range of antagonists with prototypic mu-, kappa- and sigma-opioid agonists in the tissue. Ke values for 5 antagonists against normorphine in the isolated mouse vas deferens showed excellent correlation with Ke values obtained against the mu-agonist RX783030 in the RVD. RX783030 could be effectively antagonised by naltrexone in the RVD but not by the sigma-antagonist ICI 154129 whereas D-Ala2,D-Leu5-enkephalin required both antagonists to yield parallel shifts of its dose response. The lack of agonist activity of morphine is a result of the low intrinsic activity of this agent in the RVD. The kappa-agonists ethylketocyclazocine, tifluadom and U50488 also showed antagonist properties in the RVD. These results can be rationalised by postulating that the RVD contains a mu-receptor population with a high intrinsic activity requirement together with some sigma-receptors. It is not necessary to propose the existence of a novel epsilon-receptor in order to rationalise the data reported.

Photoaffinity probes for opiate receptors: synthesis and properties of a nitro-azido-derivative of 14-beta-aminomorphinone.

The potential photoaffinity ligand 14-beta-(o-nitro, p-azido)-cinnamoyl-amino-N-cyclopropylmethylnormorphinone (NAM) and its derivative NOM, lacking the p-azido function, were synthesised and their opiate receptor activity determined in isolated tissue preparations. The ligands showed slow receptor kinetics. NAM was a pure competitive antagonist of met5-enkephalin responses in MVD while its antagonism of normorphine responses in GPI appeared non-competitive and non-reversible. In radioligand binding assays NOM completely and irreversibly blocked specific binding of 3H-DHM. Partial blockade of 3H-DADL specific binding was reversible by washing. No binding of NOM to kappa sites was observed. The slow receptor kinetics of NAM preclude its use as a photoaffinity ligand but suggest that a chemically more stable derivative may have a role as a pseudocovalent blocker of mu-receptors.

Analogues of beta-LPH61-64 possessing selective agonist activity at mu-opiate receptors.

Peptides based in the stabilised tetrapeptide HTyr-D-Ala-Gly-MePheOH have been synthesised and shown to have substantial opioid activity both in vitro and in vivo. The selectivity of these compounds of different receptor populations has been investigated using both isolated tissue assays and binding studies. Results suggest that the compounds are potent agonists at mu-receptors with little or no affinity for the delta-receptor population. One of the compounds, RX783006 (HTyr-D-Ala-Gly-MePhe-NH(CH2)2OH), has been tritiated to high specific radioactivity and may prove to be a useful probe in the elucidation of the function of the heterogenous opiate receptor population.

Biotransformation of tolmesoxide in animals and man.

1. The excretion and metabolism of tolmesoxide ((4,5-dimethoxy-2-methylphenyl)-methylsulphoxide) has been studied in rat, dog and man. In all species, absorption of oral doses of [14C]tolmesoxide was virtually complete and 78--99% of the 14C was excreted in the urine. 2. In bile-duct cannulated rats, excretion in bile and urine was 49% and 53% dose respectively. Metabolites of tolmesoxide in bile undergo enterohepatic circulation with final elimination by the kidneys. 3. Quantification and identification of metabolites in urine (0-24 h) were obtained by two-dimensional t.l.c. Tolmesoxide was extensively metabolized in all animal species. 4. The major routes of metabolism in rat, dog and man were oxidation to sulphones and O-demethylation followed by sulphate or glucuronide conjugation. Little or none of the urinary 14C was present as sulphide derivatives.

The radioimmunoassay of buprenorphine.

Antisera to buprenorphine were obtained in rabbits immunised with 3-0-carboxymethylbuprenorphine and N-hemisuccinyl-norbuprenorphine conjugated to bovine serum albumin. Using the latter antiserum and tritium labelled buprenorphine a radioimmunoassay have good accuracy and precision was developed for concentrations as low as 50 picograms in 1 ml of plasma. The N-hemisuccinyl antiserum crossreacted with norbuprenorphine, and the 3-0-glucuronide conjugate with the 3-0-carboxymethyl antiserum. Cross-reactivity of both antisera to other pharmacologically related compounds was negligible. The assay was employed to determine plasma buprenorphine concentration following its parenteral administration to dog and man.

Species differences in the metabolism and excretion of fenclofenac.

1. The excretion and metabolism of radiolabelled fenclofenac (2-(2,4-dichlorophenoxy)phenylacetic acid, Flenac) has been studied in five species. 2. In the rat, absorption of oral doses of fenclofenac was virtually complete and elimination occurred mainly by the bile and faeces. The guinea-pig excreted equal amounts of radioactivity in urine and faeces, while in rabbit, baboon and man renal excretion was the more important route. 3. In all species the majority of excreted radioactivity was present as fenclofenac ester glucuronide. Amino acid conjunction with fenclofenac was minimal in all species studied. 4. Mono- and di-hydroxylated metabolites have been detected in urine from guinea-pig, baboon and man. The major hydroxylated metabolite in baboon urine has been identified as 2-(2,4-dichlorophenoxy)-5'-hydroxyphenylacetic acid.