Complete Reaction Phenotyping of Propranolol and 4-Hydroxypropranolol with the 19 Enzymes of the Human UGT1 and UGT2 Families.

Propranolol is a competitive non-selective beta-receptor antagonist that is available on the market as a racemic mixture. In the present study, glucuronidation of propranolol and its equipotent phase I metabolite 4-hydroxypropranolol by all 19 members of the human UGT1 and UGT2 families was monitored. UGT1A7, UGT1A9, UGT1A10 and UGT2A1 were found to glucuronidate propranolol, with UGT1A7, UGT1A9 and UGT2A1 mainly acting on (S)-propranolol, while UGT1A10 displays the opposite stereoselectivity. UGT1A7, UGT1A9 and UGT2A1 were also found to glucuronidate 4-hydroxypropranolol. In contrast to propranolol, 4-hydroxypropranolol was found to be glucuronidated by UGT1A8 but not by UGT1A10. Additional biotransformations with 4-methoxypropanolol demonstrated different regioselectivities of these UGTs with respect to the aliphatic and aromatic hydroxy groups of the substrate. Modeling and molecular docking studies were performed to explain the stereoselective glucuronidation of the substrates under study.

Effect of the rigidification of propranolol, a mixed ß-adrenoceptor and 5-HT1AR antagonist.

Propranolol is a popular ß adrenergic antagonists that, together with pindolol, binds also to serotoninergic receptors, namely 5-HT1A/B. In this work the rigidification of the propranolol structure by locking its hydroxyl group within a 1,3-dioxolane ring was investigated. Constrained derivatives of propranolol were synthesized, fully characterized and tested for their affinity at ß-adrenoreceptors and 5-HT1A/B/C receptors using radioligand binding assay. The constrained derivatives were inactive, as expected, at ß1/2/3 adrenergic receptors. Although less expected, these derivatives failed to bind also to 5-HT1A/B/C receptors. The rigidification of propranolol is detrimental for 5-HT1AR activity.

Enantioselective Binding of Propranolol and Analogues Thereof to Cellobiohydrolase Cel7A.

At the catalytic site for the hydrolysis of cellulose the enzyme cellobiohydrolase Cel7A binds the enantiomers of the adrenergic beta-blocker propranolol with different selectivity. Methyl-to-hydroxymethyl group modifications of propranolol, which result in higher affinity and improved selectivity, were herein studied by 1 H,1 H and 1 H,13 C scalar spin-spin coupling constants as well as utilizing the nuclear Overhauser effect (NOE) in conjunction with molecular dynamics simulations of the ligands per se, which showed the presence of all-antiperiplanar conformations, except for the one containing a vicinal oxygen-oxygen arrangement governed by the gauche effect. For the ligand-protein complexes investigated by NMR spectroscopy using, inter alia, transferred NOESY and saturation-transfer difference (STD) NMR experiments the S-isomers were shown to bind with a higher affinity and a conformation similar to that preferred in solution, in contrast to the R-isomer. The fact that the S-form of the propranolol enantiomer is pre-arranged for binding to the protein is also observed for a crystal structure of dihydroxy-(S)-propranolol and Cel7A presented herein. Whereas the binding of propranolol is entropy driven, the complexation with the dihydroxy analogue is anticipated to be favored also by an enthalpic term, such as for its enantiomer, that is, dihydroxy-(R)-propranolol, because hydrogen-bond donation replaces the corresponding bonding from hydroxyl groups in glucosyl residues of the natural substrate. In addition to a favorable entropy component, albeit lesser in magnitude, this represents an effect of enthalpy-to-entropy compensation in ligand-protein interactions.

Selectivity in the Efflux of Glucuronides by Human Transporters: MRP4 Is Highly Active toward 4-Methylumbelliferone and 1-Naphthol Glucuronides, while MRP3 Exhibits Stereoselective Propranolol Glucuronide Transport.

Xenobiotic and endobiotic glucuronides, which are generated in hepatic and intestinal epithelial cells, are excreted via efflux transporters. Multidrug resistance proteins 2-4 (MRP2-MRP4) and the breast cancer resistance protein (BCRP) are efflux transporters that are expressed in these polarized cells, on either the basolateral or apical membranes. Their localization, along with expression levels, affects the glucuronide excretion pathways. We have studied the transport of three planar cyclic glucuronides and glucuronides of the two propranolol enantiomers, by the vesicular transport assay, using vesicles from baculovirus-infected insect cells expressing human MRP2, MRP3, MRP4, or BCRP. The transport of estradiol-17ß-glucuronide by recombinant MRP2-4 and BCRP, as demonstrated by kinetic values, were within the ranges previously reported. Our results revealed high transport rates and apparent affinity of MRP4 toward the glucuronides of 4-methylumbelliferone, 1-naphthol, and 1-hydroxypyrene (Km values of 168, 13, and 3 µM, respectively) in comparison to MRP3 (Km values of 278, 98, and 8 µM, respectively). MRP3 exhibited lower rates, but stereoselective transport of propranolol glucuronides, with higher affinity toward the R-enantiomer than the S-enantiomer (Km values 154 vs 434 µM). The glucuronide of propranolol R-enantiomer was not significantly transported by either MRP2, MRP4, or BCRP. Of the tested small glucuronides in this study, BCRP transported only 1-hydroxypyrene glucuronide, at very high rates and high apparent affinity (Vmax and Km values of 4400 pmol/mg/min and 11 µM). The transport activity of MRP2 with all of the studied small glucuronides was relatively very low, even though it transported the reference compound, estradiol-17ß-glucuronide, at a high rate (Vmax = 3500 pmol/mg/min). Our results provide new information, at the molecular level, of efflux transport of the tested glucuronides, which could explain their disposition in vivo, as well as provide new tools for in vitro studies of MRP3, MRP4, and BCRP.

Multifunctional Cinnamic Acid Derivatives.

Our research to discover potential new multitarget agents led to the synthesis of 10 novel derivatives of cinnamic acids and propranolol, atenolol, 1-adamantanol, naphth-1-ol, and (benzylamino) ethan-1-ol. The synthesized molecules were evaluated as trypsin, lipoxygenase and lipid peroxidation inhibitors and for their cytotoxicity. Compound 2b derived from phenoxyphenyl cinnamic acid and propranolol showed the highest lipoxygenase (LOX) inhibition (IC50 = 6 µΜ) and antiproteolytic activity (IC50 = 0.425 µΜ). The conjugate 1a of simple cinnamic acid with propranolol showed the higher antiproteolytic activity (IC50 = 0.315 µΜ) and good LOX inhibitory activity (IC50 = 66 µΜ). Compounds 3a and 3b, derived from methoxylated caffeic acid present a promising combination of in vitro inhibitory and antioxidative activities. The S isomer of 2b also presented an interesting multitarget biological profile in vitro. Molecular docking studies point to the fact that the theoretical results for LOX-inhibitor binding are identical to those from preliminary in vitro study.

Re-Designing of Existing Pharmaceuticals for Environmental Biodegradability: A Tiered Approach with ß-Blocker Propranolol as an Example.

Worldwide, contamination of aquatic systems with micropollutants, including pharmaceuticals, is one of the challenges for sustainable management of water resources. Although micropollutants are present at low concentrations, many of them raise considerable toxicological concerns, particularly when present as components of complex mixtures. Recent research has shown that this problem cannot be sustainably solved with advanced effluent treatment. Therefore, an alternative that might overcome these environmental problems is the design of new pharmaceutical molecules or the redesign of existing pharmaceutical molecules that present the functionality needed for their application and have improved environmental biodegradability. Such redesigning can be performed by small molecular changes in the drug molecule with intact drug moiety which could incorporate the additional attribute such as biodegradability while retaining its pharmacological potency. This proof of concept study provides an approach for the rational redesign of a given pharmaceutical (Propranolol as an example). New derivatives with small molecular changes as compared to propranolol molecule were generated by a nontargeted photolysis process. Generated derivatives with intact drug moieties (an aromatic ring and a ß-ethanolamine moiety) were further screened for aerobic biodegradability and pharmacological potency. The feasibility of the approach of redesigning an existing pharmaceutical through nontargeted generation of new derivatives with intact drug moiety and through subsequent screening was demonstrated in this study. Application of such approaches in turn might contribute to the protection of water resources in a truly sustainable manner.

Evaluation of the Effect of 1,3-Bis(4-Phenyl)-1H-1,2,3-Triazolyl-2-Propanolol on Gene Expression Levels of JAK2-STAT3, NF-κB, and SOCS3 in Cells Cultured from Biopsies of Mammary Lesions.

Breast cancer is the most frequent neoplasia in women and is responsible for approximately 13.8% of deaths per year for this gender. It has been suggested that JAK2, STAT3, and NF-κB gene expression is involved in this type of cancer. The objective of the present study was to determine the effect of bistriazole in these signaling pathways in patients with breast cancer and benign mammary lesions. The inhibitory concentration 50 of bistriazole was calculated in cell cultures of patients with benign lesions, Probit = 4.6 µM with IC = 95%. The study was performed by examining 63 women who submitted to mammary biopsies. Biopsies of the mammary lesions were performed, gene expression was determined, and cells were cultured in the presence of 4.6 µM bistriazole. We found that breast cancer is related to age greater than 50 (P ≤ 0.01), being overweight (P ≤ 0.023) and having a waist circumference larger than 80 cm (P ≤ 0.01). The gene expression of JAK2, STAT3, and NF-κB was higher in groups of patients with breast cancer, while SOCS3 expression was lower. After being exposed to bistriazole, the expression of JAK2 and STAT3 decreased, and the expression of SOCS3 and NF-κB increased. In conclusion, this molecule in development has an effect on the gene expression of JAK3 and STAT3; nevertheless, the lack of change in NF-κB indicates that it is not a regulator of inflammation, and therefore, more studies should be performed.

Angiotensin II promotes iron accumulation and depresses PGI2 and NO synthesis in endothelial cells: effects of losartan and propranolol analogs.

Angiotensin may promote endothelial dysfunction through iron accumulation. To research this, bovine endothelial cells (ECs) were incubated with iron (30 µmol·L⁻¹) with or without angiotensin II (100 nmol·L⁻¹). After incubation for 6 h, it was observed that the addition of angiotensin enhanced EC iron accumulation by 5.1-fold compared with a 1.8-fold increase for cells incubated with iron only. This enhanced iron uptake was attenuated by losartan (100 nmol·L⁻¹), d-propranolol (10 µmol·L⁻¹), 4-HO-propranolol (5 µmol·L⁻¹), and methylamine, but not by vitamin E or atenolol. After 6 h of incubation, angiotensin plus iron provoked intracellular oxidant formation (2'7'-dichlorofluorescein diacetate (DCF-DA) fluorescence) and elevated oxidized glutathione; significant loss of cell viability occurred at 48 h. Stimulated prostacyclin release decreased by 38% (6 h) and NO synthesis was reduced by 41% (24 h). Both oxidative events and functional impairment were substantially attenuated by losartan or d-propranolol. It is concluded that angiotensin promoted non-transferrin-bound iron uptake via AT-1 receptor activation, leading to EC oxidative functional impairment. The protective effects of d-propranolol and 4-HO-propranolol may be related to their lysosomotropic properties.

Streamlined Target Deconvolution Approach Utilizing a Single Photoreactive Chloroalkane Capture Tag.

Identification of physiologically relevant targets for lead compounds emerging from drug discovery screens is often the rate-limiting step toward understanding their mechanism of action and potential for undesired off-target effects. To this end, we developed a streamlined chemical proteomic approach utilizing a single, photoreactive cleavable chloroalkane capture tag, which upon attachment to bioactive compounds facilitates selective isolation of their respective cellular targets for subsequent identification by mass spectrometry. When properly positioned, the tag does not significantly affect compound potency and membrane permeability, allowing for binding interactions with the tethered compound (probe) to be established within intact cells under physiological conditions. Subsequent UV-induced covalent photo-cross-linking "freezes" the interactions between the probe and its cellular targets and prevents their dissociation upon cell lysis. Targets cross-linked to the capture tag are then efficiently enriched through covalent capture onto HaloTag coated beads and subsequent selective chemical release from the solid support. The tag's built-in capability for selective enrichment eliminates the need for ligation of a capture tag, thereby simplifying the workflow and reducing variability introduced through additional operational steps. At the same time, the capacity for adequate cross-linking without structural optimization permits modular assembly of photoreactive chloroalkane probes, which reduces the burden of customized chemistry. Using three model compounds, we demonstrate the capability of this approach to identify known and novel cellular targets, including those with low affinity and/or low abundance as well as membrane targets with several transmembrane domains.

Development of a novel system for estimating human intestinal absorption using Caco-2 cells in the absence of esterase activity.

Both mRNA and protein levels of the carboxylesterase (CES) isozymes, hCE1 and hCE2, in Caco-2 cells increase in a time-dependent manner, but hCE1 levels are always higher than those of hCE2. In human small intestine, however, the picture is reversed, with hCE2 being the predominant isozyme. Drugs hydrolyzed by hCE1 but not by hCE2 can be hydrolyzed in Caco-2 cells, but they are barely hydrolyzed in human small intestine. The results in Caco-2 cells can be misleading as a predictor of what will happen in human small intestine. In the present study, we proposed a novel method for predicting the absorption of prodrugs in the absence of CES-mediated hydrolysis in Caco-2 cells. The specific inhibition against CES was achieved using bis-p-nitrophenyl phosphate (BNPP). The optimal concentration of BNPP was determined at 200 microM by measuring the transport and hydrolysis of O-butyryl-propranolol (butyryl-PL) as a probe. BNPP concentrations of more than 200 microM inhibited 86% of hydrolysis of butyryl-PL, resulting in an increase in its apparent permeability. Treatment with 200 microM BNPP did not affect paracellular transport, passive diffusion, or carrier-mediated transport. Furthermore, the proposed evaluation system was tested for ethyl fexofenadine (ethyl-FXD), which is a superior substrate for hCE1 but a poor one for hCE2. CES-mediated hydrolysis of ethyl-FXD was 94% inhibited by 200 microM BNPP, and ethyl-FXD was passively transported as an intact prodrug. From the above observations, the novel evaluation system is effective for the prediction of human intestinal absorption of ester-type prodrugs.

Box-Behnken design for the optimization of an enantioselective method for the simultaneous analysis of propranolol and 4-hydroxypropranolol by CE.

An experimental design optimization (Box-Behnken design, BBD) was used to develop a CE method for the simultaneous resolution of propranolol (Prop) and 4-hydroxypropranolol enantiomers and acetaminophen (internal standard). The method was optimized using an uncoated fused silica capillary, carboxymethyl-beta-cyclodextrin (CM-beta-CD) as chiral selector and triethylamine/phosphoric acid buffer in alkaline conditions. A BBD for four factors was selected to observe the effects of buffer electrolyte concentration, pH, CM-beta-CD concentration and voltage on separation responses. Each factor was studied at three levels: high, central and low, and three center points were added. The buffer electrolyte concentration ranged from 25 to 75 mM, the pH ranged from 8 to 9, the CM-beta-CD concentration ranged from 3.5 to 4.5% w/v, and the applied run voltage ranged from 14 to 20 kV. The responses evaluated were resolution and migration time for the last peak. The obtained responses were processed by Minitab to evaluate the significance of the effects and to find the optimum analysis conditions. The best results were obtained using 4% w/v CM-beta-CD in 25 mM triethylamine/H3PO4 buffer at pH 9 as running electrolyte and 17 kV of voltage. Resolution values of 1.98 and 1.95 were obtained for Prop and 4-hydroxypropranolol enantiomers, respectively. The total analysis time was around of 15 min. The BBD showed to be an adequate design for the development of a CE method, resulting in a rapid and efficient optimization of the pH and concentration of the buffer, cyclodextrin concentration and applied voltage.

Enantioselective analysis of propranolol and 4-hydroxypropranolol by CE with application to biotransformation studies employing endophytic fungi.

A CE method is described for the enantioselective analysis of propranolol (Prop) and 4-hydroxypropranolol (4-OH-Prop) in liquid Czapek medium with application in the study of the enantioselective biotransformation of Prop by endophytic fungi. The electrophoretic conditions previously optimized were as follows: an uncoated fused-silica capillary, 4% w/v carboxymethyl-beta-CD in 25 mmol/L triethylamine/phosphoric acid (H(3)PO(4)) buffer at pH 9 as running electrolyte and 17 kV of voltage. UV detection was carried out at 208 nm. Liquid-liquid extraction using diethyl ether: ethyl acetate (1:1 v/v) as extractor solvent was employed for sample preparation. The calibration curves were linear over the concentration range of 0.25-10.0 microg/mL for each 4-OH-Prop enantiomer and 0.10-10.0 microg/mL for each Prop enantiomer (r>or=0.995). Within-day and between-day relative standard deviations and relative errors for precision and accuracy were lower than 15% for all the enantiomers. Finally, the validated method was used to evaluate Prop biotransformation in its mammalian metabolite 4-OH-Prop by some selected endophytic fungi. The screening of five strains of endophytic fungi was performed and all of them could biotransform Prop to some extent. Specifically, Glomerella cingulata (VA1) biotransformed 47.8% of (-)-(S)-Prop to (-)-(S)-4-OH-Prop with no formation of (+)-(R)-4-OH-Prop in 72 h of incubation.

Regioselective preparation of 5-hydroxypropranolol and 4'-hydroxydiclofenac with a fungal peroxygenase.

An extracellular peroxygenase of Agrocybe aegerita catalyzed the H(2)O(2)-dependent hydroxylation of the multi-function beta-adrenergic blocker propranolol (1-naphthalen-1-yloxy-3-(propan-2-ylamino)propan-2-ol) and the non-steroidal anti-inflammatory drug diclofenac (2-[2-[(2,6-dichlorophenyl)amino]phenyl]acetic acid) to give the human drug metabolites 5-hydroxypropranolol (5-OHP) and 4'-hydroxydiclofenac (4'-OHD). The reactions proceeded regioselectively with high isomeric purity and gave the desired 5-OHP and 4'-OHD in yields up to 20% and 65%, respectively. (18)O-labeling experiments showed that the phenolic hydroxyl groups in 5-OHP and 4'-OHD originated from H(2)O(2), which establishes that the reaction is mechanistically a peroxygenation. Our results raise the possibility that fungal peroxygenases may be useful for versatile, cost-effective, and scalable syntheses of drug metabolites.

pH dependency of ligand binding to cellobiohydrolase 1 (Cel7A). Affinity, selectivity and inhibition for designed propranolol analogues.

The affinity and enantioselectivity have been determined for designed propranolol derivatives as ligands for Cel7A by capillary electrophoresis (CE) at pH 7.0. These results have been compared to measurements at pH 5.0. In agreement with previous studies, the affinity increased at the higher pH. However, the affinity was not as dependent of the ligand structure at pH 7.0 as at pH 5.0, and the selectivity was generally decreased. Instead, at pH 7.0, the changes in binding were mainly dependent on the presence of additional dihydroxyl groups, indicating an increased importance of the electrostatic interactions. To evaluate the pH dependent variations in binding, changes in both the ligand and in the enzyme had to be taken into account. To ensure that the ligands had the same charge in all measurements, pKa-values of all compounds were determined. The ligand-protein interaction has also been studied by inhibition experiments at both pHs to evaluate the specific binding to the active site when competing with the substrate p-nitrophenyl lactoside (pNPL). With support of docking computations we propose a hypothesis on the effect of the ligand structure and pH dependency of the binding and selectivity of amino alcohols to Cel7A.

Induction of propranolol metabolism by Ginkgo biloba extract EGb 761 in rats.

Ginkgo biloba is one of the most popular herbal medicines in the world, due to its purported pharmacological effects, including memory-enhancing, cognition-improving, and antiplatelet effects. When used in the elderly, Ginkgo has a high potential for interactions with cardiovascular drugs. This study aimed to investigate the effects of the standard Ginkgo biloba extract (EGB 761) treatment on the pharmacokinetics of propranolol and its metabolism to form N-desisopropylpropranolol (NDP) in rats. We also examined the activity and expression of cytochrome P450 (CYP) 1A and other CYPs in rats treated with EGb 761 at 10 and 100 mg/kg/day for 10 days. A single oral dose of propranolol (10 mg/kg) was administered on day 11 and the concentrations of both propranolol and NDP were determined using validated liquid chromatography-mass spectrometry (LC-MS) methods. The levels of mRNA and protein of various CYPs were determined by RT-PCR and Western blotting analysis, respectively. Pretreatment of EGb 761 at 100 mg/kg, but not 10 mg/kg, for 10 days significantly reduced the area under the plasma concentration-time curve (AUC) and maximum plasma concentration (Cmax) of propranolol, whereas those values of NDP were significantly increased. CYP1A1, 1A2, 2B1/2, and 3A1 activities and gene expression in the rat liver were significantly increased in a dose-dependent manner by pretreatment with EGb 761. The ex-vivo formation of NDP in liver microsomes from rats pretreated with EGb 761 was markedly enhanced. The formation of NDP from propranolol in liver microsomes was significantly inhibited by alpha-naphthoflavone (ANF, a selective CYP1A2 inhibitor), but not by quinidine (a CYP2D inhibitor). These results indicated that EGb 761 pretreatment decreased the plasma concentrations of propranolol by accelerated conversion of parental drug to NDP due to induction of CYP1A2. EGb 761 pretreatment also significantly induced CYP2B1/2 and CYP3A1, suggesting potential interactions with substrate drugs for these two enzymes. Further study is needed to explore the potential for gingko-drug interactions and the clinical impact.

Simultaneous quantification of propranolol and sulfamethoxazole and major human metabolite conjugates 4-hydroxy-propranolol sulfate and sulfamethoxazole-ß-glucuronide in municipal wastewater-A framework for multiple classes of drugs and conjugates.

Recent data suggests there are non-trivial amounts of human pharmaceutical conjugates potentially entering environmental surface waters. These compounds could contribute to eliciting toxic effects on aquatic biota either directly or indirectly, via de-conjugation. The need for developing a single method for quantifying both parents and conjugates is necessary. Propranolol (PRO), sulfamethoxazole (SMX), and their respective major conjugates 4-OH-propranolol sulfate (PRO-Sul) and sulfamethoxazole-ß-glucuronide (SMX-Glc) were successfully simultaneously extracted through weak anion exchange solid phase extraction cartridges from primary and secondary clarification wastewaters from the North End Winnipeg Water Pollution Treatment Plant in Winnipeg, Canada. Subsequent separation and quantification were achieved by reversed-phase C18 chromatography coupled to positive electrospray ionisation tandem mass spectrometry. Linearity for all compounds throughout the 7-point calibration range was >0.99. Recovery RSD ranges across all matrices for PRO, SMX, PRO-Sul, and SMX-Glc were 2.1-13.2%, 2.3-10.2%, 9.8-19.2%, and 2.0-10.3% respectively. Primary and secondary filtrates respectively showed a significant increase of PRO from 0.039 to 0.045µg/L; a significant decrease for SMX from 1.56 to 0.58µg/L; significant decrease of PRO-Sul from 0.050 to 0.020µg/L; and a significant decrease of SMX-Glc from 0.41 to 0.019µg/L. These observations indicate that there was removal of all compounds, except for PRO, from the aqueous phase occurring at some point between the stages of treatment. To our knowledge, this is first study that simultaneously separated and quantified two different classes of parent compounds and two different kinds of human metabolite conjugates (glucuronide and sulfate) from a major urban wastewater treatment plant.

Binding of dansyl propranolol to the (Ca2+ + Mg2+)-ATPase.

We have studied the binding of dansyl propranolol to lipid bilayers and to the (Ca2+ + Mg2+)-ATPase of sarcoplasmic reticulum. The fluorescence emission spectra for dansyl propranolol bound to the ATPase system can be fitted to the sum of three peaks, characteristic of probe bound to lipid and to protein and free in solution, respectively. Titrations show that binding to the lipid component of the ATPase system is comparable to binding to simple lipid bilayers. Binding constants obtained using fluorescence spectroscopy for binding to lipid bilayers agree with constants obtained from microelectrophoresis measurements. Binding to sites on the ATPase can be described either in terms of the aqueous concentration of dansyl propranolol or in terms of the mole fraction of dansyl propranolol in the lipid phase of the membrane. Both descriptions suggest extensive binding to annular sites at the lipid/protein interface of the ATPase. Binding at other sites on the ATPase might also be present. Binding of dansyl propranolol to the ATPase results in a marked inhibition of activity. At high Ca2+ concentrations, inhibition fits to a non-competitive model of inhibition, described by a Ki of 5 microM. We attribute this effect to binding at annular sites. At lower Ca2+ concentration, a decrease is observed in the apparent affinity of the ATPase for Ca2+ which can be attributed to a build-up of positive charge on the membrane as a result of binding.

Involvement of SULT1A3 in elevated sulfation of 4-hydroxypropranolol in Hep G2 cells pretreated with beta-naphthoflavone.

Pretreatment of Hep G2 cells with beta-naphthoflavone (BNF 1-25microM) significantly increased cytosolic sulfation activities of 4-hydroxypropranolol (4-OH-PL) racemate. The profile was similar to those of sulfations towards dopamine and triiodothyronine in the same cytosolic fractions. Kinetic studies of 4-OH-PL sulfation in Hep G2 cytosolic fractions revealed that V(max) values increased but apparent K(m) values remained unchanged following the BNF pretreatment. Among five recombinant human SULT isoforms (SULT1A1, -1A3, -1B1, -1E1 and -2A1) examined, only SULT2A1 did not show 4-OH-PL sulfation activities under the conditions used. SULT1A3 and -1E1 exhibited an enantioselectivity of 4-OH-R-PL sulfation>4-OH-S-PL sulfation, which agreed with that of BNF-pretreated Hep G2 cells as well as of nontreated cells, whereas SULT1A1 and -1B1 showed a reversed enantioselectivity (R

Candida rugosa lipase-catalyzed intramolecular O- to N- transacylation of butyryl propranolol in the presence of cyclodextrins.

In the present paper, a novel enzymatic reaction between (R,S)-O-butyryl propranolol (O-BP) and lipase from Candida rugosa in the presence of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) is described. Under the used condition, lipase catalyzed the intramolecular transacylation of O-BP into N-butyryl propranolol (N-BP). Propranolol, the product of the expected hydrolysis reaction, was not detected in the reaction medium. A chiral analysis of the reaction product indicated that lipase showed a preference for (R)-O-butyryl propranolol since it first transformed the (R)-enantiomer and then the corresponding (S)-enantiomer. The influence of different reaction conditions on the initial rate is also studied.

Stereoselective urinary excretion of S-(-)- and R-(+)-propranolol glucuronide following oral administration of RS-propranolol in Chinese Han subjects.

AIM: To study the stereoselectivity of phase II glucuronidation metabolism of side-chain propranolol in Chinese Han population. METHODS: Sixteen adult Chinese Han volunteers with an average age of 20 years were given a single oral dose of 20 mg racemic propranolol. Human urine at indicated time after administration was collected and S-(-)-propranolol glucuronide and R-(+)-propranolol glucuronide were determined simultaneously by using RP-HPLC. RESULTS: The mean values of k were 0.19+/-0.04 h(-1) and 0.28+/-0.06 h(-1), of t(1/2) 3.56+/-0.73 h and 2.45+/-0.50 h, of T(max) 2.21+/-0.45 and 1.75+/-0.33 h, and of Xu(0-24) 5.65+/-0.98 and 2.95+/-0.62 micromoL for S-(-)- and R-(+)-propranolol glucuronide, respectively. The cumulative excretion percentages in urine of doses were 14.7+/-2.46% and 7.68+/-1.60% for S-(-)- and R-(+)-propranolol glucuronide, respectively. The results showed the elimination rate constant k of S-(-)-propranolol glucuronide was less than that of R-(+)-propranolol glucuronide; and the elimination half-life (t(1/2)), T(max) and the cumulative excretion amount(Xu(0-24)) of R-(+)-propranolol glucuronide were significantly less than that of S-(-)-propranolol glucuronide. CONCLUSION: The propranolol glucuronidation of the side-chain undergoes stereoselective excretion in Chinese Han population after an oral administration of racemic propranolol.