Synthesis, Anticonvulsant, and Antinociceptive Activity of New 3-(2-Chlorophenyl)- and 3-(3-Chlorophenyl)-2,5-dioxo-pyrrolidin-1-yl-acetamides.

The new series of 3-(2-chlorophenyl)- and 3-(3-chlorophenyl)-pyrrolidine-2,5-dione-acetamide derivatives as potential anticonvulsant and analgesic agents was synthesized. The compounds obtained were evaluated in the following acute models of epilepsy: maximal electroshock (MES), psychomotor (6 Hz, 32 mA), and subcutaneous pentylenetetrazole (scPTZ) seizure tests. The most active substance-3-(2-chlorophenyl)-1-{2-[4-(4-fluorophenyl)piperazin-1-yl]-2-oxoethyl}-pyrrolidine-2,5-dione (6) showed more beneficial ED50 and protective index values than the reference drug-valproic acid (68.30 mg/kg vs. 252.74 mg/kg in the MES test and 28.20 mg/kg vs. 130.64 mg/kg in the 6 Hz (32 mA) test, respectively). Since anticonvulsant drugs are often effective in neuropathic pain management, the antinociceptive activity for two the promising compounds-namely, 6 and 19-was also investigated in the formalin model of tonic pain. Additionally, for the aforementioned compounds, the affinity for the voltage-gated sodium and calcium channels, as well as GABAA and TRPV1 receptors, was determined. As a result, the most probable molecular mechanism of action for the most active compound 6 relies on interaction with neuronal voltage-sensitive sodium (site 2) and L-type calcium channels. Compounds 6 and 19 were also tested for their neurotoxic and hepatotoxic properties and showed no significant cytotoxic effect.

The Rise of Synaptic Density PET Imaging.

Many neurological disorders are related to synaptic loss or pathologies. Before the boom of positrons emission tomography (PET) imaging of synapses, synaptic quantification could only be achieved in vitro on brain samples after autopsy or surgical resections. Until the mid-2010s, electron microscopy and immunohistochemical labelling of synaptic proteins were the gold-standard methods for such analyses. Over the last decade, several PET radiotracers for the synaptic vesicle 2A protein have been developed to achieve in vivo synapses visualization and quantification. Different strategies were used, namely radiolabelling with either 11C or 18F, preclinical development in rodent and non-human primates, and binding quantification with different kinetic modelling methods. This review provides an overview of these PET tracers and underlines their perspectives and limitations by focusing on radiochemical aspects, as well as preclinical proof-of-concept and the main clinical outcomes described so far.

Isolation from Stevia rebaudiana of DMDP acetic acid, a novel iminosugar amino acid: synthesis and glycosidase inhibition profile of glycine and ß-alanine pyrrolidine amino acids.

DMDP acetic acid [N-carboxymethyl-2,5-dideoxy-2,5-imino-D-mannitol] 5 from Stevia rebaudiana is the first isolated natural amino acid derived from iminosugars bearing an N-alkyl acid side chain; it is clear from GCMS studies that such derivatives with acetic and propionic acids are common in a broad range of plants including mulberry, Baphia, and English bluebells, but that they are very difficult to purify. Reaction of unprotected pyrrolidine iminosugars with aqueous glyoxal gives the corresponding N-acetic acids in very high yield; Michael addition of both pyrrolidine and piperidine iminosugars and that of polyhydroxylated prolines to tert-butyl acrylate give the corresponding N-propionic acids in which the amino group of ß-alanine is incorporated into the heterocyclic ring. These easy syntheses allow the identification of this new class of amino acid in plant extracts and provide pure samples for biological evaluation. DMDP N-acetic and propionic acids are potent α-galactosidase inhibitors in contrast to potent ß-galactosidase inhibition by DMDP.

[Insecticidal action of synthetic girgensohnine analogues and essential oils on Rhodnius prolixus (Hemiptera: Reduviidae)].

INTRODUCTION: The alkaloid girgensohnine has been used as a natural model in the synthesis of new alkaloid-like alpha-aminonitriles with insecticidal effect against disease vectors. OBJECTIVE: To evaluate the biocide activity of girgensohnine analogues and essential oils of Cymbopogon flexuosus, Citrus sinensis and Eucalyptus citriodora in stage I and stage V Rhodnius prolixus nymphs. MATERIALS AND METHODS: We used a topical application model in tergites and sternites, as well as exposure to treated surfaces with different exploratory doses of each of the molecules and essential oils to determine the lethal doses (LD50 and LD95). RESULTS: Analogue 3 showed the highest insecticidal activity with 83.3±16.7% of mortality when applied on tergites, 38.9±4.8% on sternites and 16.7±0% on treated surfaces in stage I nymphs at 72 hours (h) and 500 mg.L-1. In stage V nymphs, the compounds induced mortality only in sternums (11.1±9.6% for analogue 6 and 5.5±4.7% for analogues 3 and 7 at 72 h and 1500 mg.L-1). The lethal doses for molecule 3 on tergites in stage I nymphs were LD50 225.60 mg.L-1 and LD95 955.90 mg.L-1. The insecticidal effect of essential oils was observed only in stage I nymphs, with 11.1±4.8% for C. flexuosus when applied in sternites, while using exposure to surfaces treated it was 5.6±4.8% for C. sinensis applied on tergites and 8.3±0% on sternites at 72 h and 1000 mg.L-1. CONCLUSION: Synthetic girgensohnine analogues, and C. flexuosus and C. sinensis essential oils showed insecticidal activity in R. prolixus. Analogue 3 showed the greatest insecticidal activity among all molecules and oils evaluated under our laboratory conditions.

Synthesis and optical properties of pyrrolidinyl peptide nucleic acid bearing a base discriminating fluorescence nucleobase 8-(pyrene-1-yl)-ethynyladenine.

A combination of fluorophore and nucleobase through a π-conjugated rigid linker integrates the base pairing and the fluorescence change into a single event. Such base discriminating fluorophore can change its fluorescence as a direct response to the base pairing event and therefore have advantages over tethered labels or base surrogates lacking the hydrogen-bonding ability. 8-(Pyrene-1-yl)ethynyl-adenine (APyE) has been extensively used as fluorescence labels in DNA and LNA, but it showed little discrimination between different nucleobases. Herein we investigated the synthesis, base pairing ability and optical properties of APyE in pyrrolidinyl peptide nucleic acid - a DNA mimic that shows much stronger affinity and specificity towards DNA than natural oligonucleotides. The APyE in PNA pairs specifically with thymine in the DNA strand, and resulted in 1.5-5.2-fold enhanced and blue-shifted fluorescence emission. Fluorescence quenching was observed in the presence of mismatched base or abasic site directly opposite to the APyE. The behavior of APyE in acpcPNA is distinctively different from DNA whereby a fluorescence was increased selectively upon duplex formation with complementary DNA and therefore emphasizing the unique advantages of using PNA as alternative oligonucleotide probes. Applications as color-shifting probe for detection of trinucleotide repeats in DNA were demonstrated, and the performance of the probe was further improved by combination with reduced graphene oxide as an external nanoquencher.

Insecticidal action of synthetic girgensohnine analogues and essential oils on Rhodnius prolixus (Hemiptera: Reduviidae) / Acción insecticida de análogos sintéticos de girgensohnina y de aceites esenciales sobre Rhodnius prolixus (Hemiptera: Reduviidae)

ABSTRACT Introduction: The alkaloid girgensohnine has been used as a natural model in the synthesis of new alkaloid-like alpha-aminonitriles with insecticidal effect against disease vectors. Objective: To evaluate the biocide activity of girgensohnine analogues and essential oils of Cymbopogon flexuosus, Citrus sinensis and Eucalyptus citriodora in stage I and stage V Rhodnius prolixus nymphs. Materials and methods: We used a topical application model in tergites and sternites, as well as exposure to treated surfaces with different exploratory doses of each of the molecules and essential oils to determine the lethal doses (LD50 and LD95). Results: Analogue 3 showed the highest insecticidal activity with 83.3±16.7% of mortality when applied on tergites, 38.9±4.8% on sternites and 16.7±0% on treated surfaces in stage I nymphs at 72 hours (h) and 500 mg.L-1. In stage V nymphs, the compounds induced mortality only in sternums (11.1±9.6% for analogue 6 and 5.5±4.7% for analogues 3 and 7 at 72 h and 1500 mg.L-1). The lethal doses for molecule 3 on tergites in stage I nymphs were LD50 225.60 mg.L-1 and LD95 955.90 mg.L-1. The insecticidal effect of essential oils was observed only in stage I nymphs, with 11.1±4.8% for C. flexuosus when applied in sternites, while using exposure to surfaces treated it was 5.6±4.8% for C. sinensis applied on tergites and 8.3±0% on sternites at 72 h and 1000 mg.L-1. Conclusion: Synthetic girgensohnine analogues, and C. flexuosus and C. sinensis essential oils showed insecticidal activity in R. prolixus. Analogue 3 showed the greatest insecticidal activity among all molecules and oils evaluated under our laboratory conditions.

RESUMEN Introducción. El alcaloide natural girgensohnina se ha usado como modelo en la síntesis de nuevos análogos de alcaloidales alfa-aminonitrílicos con efecto insecticida en vectores de enfermedades. Objetivo. Evaluar la actividad biocida de análogos de girgensohnina y de aceites esenciales de las plantas Cymbopogon flexuosus, Citrus sinensis y Eucalyptus citriodora en ninfas de estadios I y V de Rhodnius prolixus. Materiales y métodos. Se empleó la aplicación tópica en terguitos, esternitos y superficies tratadas con diferentes dosis exploratorias de cada una de las moléculas y aceites esenciales para determinar las dosis letales (LD50 y LD95). Resultados. El análogo 3 tuvo la mayor actividad insecticida, con una mortalidad de 83,3±16,7% en los terguitos, de 38,9±4,8 % en los esternitos y de 16,7±0 % a las 72 horas en ninfas de estadioI expuestas a superficies tratadas y 500 mg.L-1. En las ninfas de estadio V solo se presentó mortalidad en los esternitos (11,1±9,6 % con el análogo 6 y 5,5±4,7 % con los análogos 3 y 7 a las 72 h y 1.500 mg.L-1). Las dosis letales para la molécula 3 en los terguitos de ninfas de estadio I fueron las siguientes: DL50, 225,60 mg.L-1 y DL95, 955,90 mg.L-1. En cuanto a los aceites esenciales, el efecto insecticida solo se presentó con C. flexuosus (11,1±4,8%) en los esternitos de ninfas de estadio I expuestas a superficies tratadas; con C. sinensis (5,6±4,8%) en los terguitos y en los esternitos (8,3±0%) a las 72 horas y 1.000 mg.L-1. Conclusión. Los análogos sintéticos del alcaloide girgensohnina y los aceites esenciales de C. flexuosus y C. sinensis exhibieron actividad insecticida en R. prolixus. El análogo 3 exhibió la mayor actividad insecticida de todas las moléculas evaluadas bajo las condiciones de laboratorio.

Tuning of ß-glucosidase and α-galactosidase inhibition by generation and in situ screening of a library of pyrrolidine-triazole hybrid molecules.

The preliminary screening of two libraries of epimeric (pyrrolidin-2-yl)triazoles (14a-s and 22a-s), generated via click chemistry, allowed the rapid identification of four α-galactosidase (coffee beans) inhibitors (22b,k,p,r) and two ß-glucosidase (almond) inhibitors (14b,f) in the low µM range. The additional biological analysis of 14b,f towards ß-glucocerebrosidase (human lysosomal ß-glucosidase), as target enzyme for Gaucher disease, showed a good correlation with the inhibition results obtained for the plant (almond) enzyme. Surprisingly, although these compounds showed inhibition towards ß-glucocerebrosidase as acid hydrolase, they did not inhibit bovine liver ß-glucosidase as neutral hydrolase. In contrast to what was observed for ß-glucosidase inhibition, the coffee bean α-galactosidase inhibitors of the epimeric library (22b,k,p,r) only showed weak inhibition towards human lysosomal α-galactosidase.

The preparation and evaluation of salt forms of linogliride with reduced solubilities as candidates for extended release.

Salts of linogliride with reduced solubilities were prepared and evaluated as potential candidates for extended-release oral dosage forms. A once-daily dose of 300-800 mg was intended. Seven acids were selected: p-acetamidobenzoic, benzoic, p-hydroxybenzoic, 3-hydroxy-2-naphthoic, 1-napsylic, pamoic, and p-toluenesulfonic acids but only four salts were able to be prepared in suitable quantities for evaluation: linogliride pamoate, p-hydroxybenzoate, 3-hydroxy-2-naphthoate, and 1-napsylate. The pH-solubility profiles of the four new salts, free base, and fumarate salt were compared over the pH 1.43-8.3 range and the intrinsic dissolution rates of the four new salts and the free base were determined at pH 1.43, 4.4, and 7.5. The range of the pH-solubility profile and intrinsic dissolution rates of the p-hydroxybenzoate salt were less than the free base and fumarate and higher than the other three new salts. The pH-solubilities and intrinsic dissolution rates of the 1-napsylate salt were pH-independent. The solubilities and intrinsic dissolution rates of the pamoate and 3-hydroxy-2-naphthoate were higher at pH 1.4-3.4 than at higher pH. At pH 4.4 and higher, the solubilities were essentially the same, in the 1-2 mg/mL range. The intrinsic dissolution rates were also very low and not very different. Dissolution studies with capsules containing 800 mg doses of the pamoate, 1-napsylate, free base, and fumarate performed in a dissolution medium of pH beginning at 2.2 and ending at 6.8 demonstrated that the pamoate and 1-napsylate salt forms dissolved slower and could be useful as extended-release forms.

Discovery of novel S1P2 antagonists, part 3: Improving the oral bioavailability of a series of 1,3-bis(aryloxy)benzene derivatives.

The structure of the S1P2 antagonist 1 has been modified with the aim of improving its oral bioavailability. The chemical modification of the alkyl chain and carboxylic acid moieties of 1 led to significant improvements in the oral exposure of compounds belonging to this series. The optimization of the ring size of the urea portion of these molecules also led to remarkable improvements in the oral exposure. Based on these changes, the pyrrolidine derivative 16 was identified as a suitable candidate compound and showed excellent pharmacokinetic profiles in rat and dog, while maintaining high levels of potency and selective antagonistic activity toward S1P2.

Direct Phenotypic Screening in Mice: Identification of Individual, Novel Antinociceptive Compounds from a Library of 734,821 Pyrrolidine Bis-piperazines.

The hypothesis in the current study is that the simultaneous direct in vivo testing of thousands to millions of systematically arranged mixture-based libraries will facilitate the identification of enhanced individual compounds. Individual compounds identified from such libraries may have increased specificity and decreased side effects early in the discovery phase. Testing began by screening ten diverse scaffolds as single mixtures (ranging from 17,340 to 4,879,681 compounds) for analgesia directly in the mouse tail withdrawal model. The "all X" mixture representing the library TPI-1954 was found to produce significant antinociception and lacked respiratory depression and hyperlocomotor effects using the Comprehensive Laboratory Animal Monitoring System (CLAMS). The TPI-1954 library is a pyrrolidine bis-piperazine and totals 738,192 compounds. This library has 26 functionalities at the first three positions of diversity made up of 28,392 compounds each (26 × 26 × 42) and 42 functionalities at the fourth made up of 19,915 compounds each (26 × 26 × 26). The 120 resulting mixtures representing each of the variable four positions were screened directly in vivo in the mouse 55 °C warm-water tail-withdrawal assay (ip administration). The 120 samples were then ranked in terms of their antinociceptive activity. The synthesis of 54 individual compounds was then carried out. Nine of the individual compounds produced dose-dependent antinociception equivalent to morphine. In practical terms what this means is that one would not expect multiexponential increases in activity as we move from the all-X mixture, to the positional scanning libraries, to the individual compounds. Actually because of the systematic formatting one would typically anticipate steady increases in activity as the complexity of the mixtures is reduced. This is in fact what we see in the current study. One of the final individual compounds identified, TPI 2213-17, lacked significant respiratory depression, locomotor impairment, or sedation. Our results represent an example of this unique approach for screening large mixture-based libraries directly in vivo to rapidly identify individual compounds.

3-Hydroxypyrrolidine and (3,4)-dihydroxypyrrolidine derivatives: inhibition of rat intestinal α-glucosidase.

Thirteen pyrrolidine-based iminosugar derivatives have been synthesized and evaluated for inhibition of α-glucosidase from rat intestine. The compounds studied were the non-hydroxy, mono-hydroxy and dihydroxypyrrolidines. All the compounds were N-benzylated apart from one. Four of the compounds had a carbonyl group in the 2,5-position of the pyrrolidine ring. The most promising iminosugar was the trans-3,4-dihydroxypyrrolidine 5 giving an IC50 of 2.97±0.046 and a KI of 1.18 mM. Kinetic studies showed that the inhibition was of the mixed type, but predominantly competitive for all the compounds tested. Toxicological assay results showed that the compounds have low toxicity. Docking studies showed that all the compounds occupy the same region as the DNJ inhibitor on the enzyme binding site with the most active compounds establishing similar interactions with key residues. Our studies suggest that a rotation of ∼90° of some compounds inside the binding pocket is responsible for the complete loss of inhibitory activity. Despite the fact that activity was found only in the mM range, these compounds have served as simple molecular tools for probing the structural features of the enzyme, so that inhibition can be improved in further studies.

A novel anti-HIV active integrase inhibitor with a favorable in vitro cytochrome P450 and uridine 5'-diphospho-glucuronosyltransferase metabolism profile.

Research efforts on the human immunodeficiency virus (HIV) integrase have resulted in two approved drugs. However, co-infection of HIV with Mycobacterium tuberculosis and other microbial and viral agents has introduced added complications to this pandemic, requiring favorable drug-drug interaction profiles for antiviral therapeutics targeting HIV. Cytochrome P450 (CYP) and uridine 5'-diphospho-glucuronosyltransferase (UGT) are pivotal determining factors in the occurrence of adverse drug-drug interactions. For this reason, it is important that anti-HIV agents, such as integrase inhibitors, possess favorable profiles with respect to CYP and UGT. We have discovered a novel HIV integrase inhibitor (compound 1) that exhibits low nM antiviral activity against a diverse set of HIV-1 isolates, and against HIV-2 and the simian immunodeficiency virus (SIV). Compound 1 displays low in vitro cytotoxicity and its resistance and related drug susceptibility profiles are favorable. Data from in vitro studies revealed that compound 1 was not a substrate for UGT isoforms and that it was not an inhibitor or activator of key CYP isozymes.

Virtual screening and QSAR study of some pyrrolidine derivatives as α-mannosidase inhibitors for binding feature analysis.

Virtual screening and QSAR analysis were carried out to investigate the binding features of (2R, 3R, 4S)-2-aminomethylpyrrolidine 3,4-diol and the functionalized pyrrolidine derivatives to the α-mannosidase I and II enzymes. The QSAR models (possessed considerable R(2), Q(2) values, etc.) suggested that the presence of polar property on the vdW surface (vsurf_W, vsurf_Wp, etc.) of the molecules is important along with the presence of aromatic rings (opr_violation) in the molecules (which also provide hydrophobicity to the molecules). The docking study performed on α-mannosidase I and II enzymes pointed that the main interactions occur by hydrogen bonds, hydrophobic π-π stacking contacts and salt bridges with the cation calcium (for α-mannosidase I) and close interaction with zinc ion (α-mannosidase II), respectively. The bond flexibility orientates the aromatic ring in the molecules toward the hydrophobic cavity for π-π stacking contacts with the aromatic amino acids (Phe528, Phe329 and Phe659 for α-mannosidase I and Trp95, Tyr269, Phe312, Tyr102 for α-mannosidase II). The pharmacophore analysis also supports the results derived from the docking and QSAR studies. Our results suggest that the best compound to inhibit both classes of α-mannosidase is the compound 30, which may be used to design similar and better inhibitors to next generation drugs.

Discovery and structure-activity relationships of urea derivatives as potent and novel CCR3 antagonists.

The synthesis and structure-activity relationships of ureas as CCR3 antagonists are described. Optimization starting with lead compound 2 (IC(50)=190 nM) derived from initial screening hit compound 1 (IC(50)=600 nM) led to the identification of (S)-N-((1R,3S,5S)-8-((6-fluoronaphthalen-2-yl)methyl)-8-azabicyclo[3.2.1]octan-3-yl)-N-(2-nitrophenyl)pyrrolidine-1,2-dicarboxamide 27 (IC(50)=4.9 nM) as a potent CCR3 antagonist.

Preparation of O-methyl substituted 2-oxofuro- and 2-oxopyrrolidinoindolines by reductive lactonization of oxindol-3-ylacetic acids.

A practical procedure for the preparation of O-methyl substituted 3a,8-dialkyl-2-oxofuroindolines is described. Reductive lactonization of the corresponding oxindol-3-ylacetic acids provides a route for the formation of this class of compounds. Further transformation of 2-oxofuroindolines into 2-oxopyrrolidinoindolines, and then to pyrrolidinoindolines demonstrates their versatility as key intermediates in natural products synthesis. The results of single-crystal X-ray crystallographic analyses are given for five of the studied compounds.

Synthesis of pyrrolidinoindolines from 2-(2-oxo-3-indolyl)acetates: scope and limitations.

A series of 1,3a,8-alkylpyrrolidinoindolines have been synthesized. The scope and limitations of the alkylation of starting methyl oxindol-3-acetates are explored employing electron-rich and electron-poor alkylating agents. Hydrolysis and reductive lactonization of the resulting carboxylic gamma-oxindolic acid derivatives proceeds with good yields to afford 2-oxofuroindolines providing ready access to the pyrrolidinoindoline derivatives.

Synthesis of 4-amino-4,5-dideoxy-L-lyxofuranose derivatives and their evaluation as fucosidase inhibitors.

The nitrone 4 (4,5-dideoxy-4-hydroxylamino-3,4-O-isopropylidene-L-lyxofuranose) was synthesised from D-ribose and used as key intermediate for the preparation of fucosidase inhibitors. We describe two transformations of 4. Hydrolysis with aqueous sulfur dioxide gave the known potent nanomolar inhibitor 4-amino-4,5-dideoxy-L-lyxofuranose (3). 1,3-Dipolar cycloaddition with enol ethers led to the related 1,2,5,6-tetradeoxy-2,5-imino-L-altroheptonic ester 2a, acid 2b and the corresponding heptitol 2c. The new iminosugars have been evaluated for their inhibitory activity against α-L-fucosidase from bovine kidney. The alcohol 2c turned out to be a potent inhibitor in the same range as the amino-sugar 3 (K(i)=8 vs 10nM).

Exploration of (S)-3-aminopyrrolidine as a potentially interesting scaffold for discovery of novel Abl and PI3K dual inhibitors.

Based on the literature-reported compensatory effect of PI3K on Abl inhibition and the improved preclinical effect of drug combination of Abl and PI3K inhibitors, a series of compounds bearing novel scaffold of (S)-3-aminopyrrolidine was identified as Abl and PI3K dual inhibitors through support vector machine screening tool, which were subsequently synthesized and tested. Most compounds demonstrated promising cytoxicity against a CML leukemia cell-line K562 and moderate inhibition against Abl and PI3K kinases. These compounds induced no apoptosis in K562 cell-line, suggesting that their cytotoxic activities are unlikely duo to other known anti-CML mechanisms. Molecular docking study further showed that the compound 5k could bind with both Abl and PI3K, but the weaker binding with Abl compared to Imatinib is consistent with its low kinase inhibitory rates. These plus literature-reported evidences suggest that the promising cytotoxic effect of our novel compounds might be due to the collective effect of Abl and PI3K inhibition.

Selective antagonists of mouse trace amine-associated receptor 1 (mTAAR1): discovery of EPPTB (RO5212773).

High throughput screening of the Roche compound library identified benzanilides such as 1 and 2 as antagonists of TAAR1. Optimisation of this hit series led to the first selective TAAR1 antagonist (N-(3-Ethoxy-phenyl)-4-pyrrolidin-1-yl-3-trifluoromethyl-benzamide EPPTB (RO5212773, 9f) having IC(50) of 28 nM at mouse TAAR1.

Synthesis of all-cis 2,5-imino-2,5-dideoxy-fucitol and its evaluation as a potent fucosidase and galactosidase inhibitor.

We here describe a simple and efficient synthetic method for a non-hydrolysable precursor of a GDP-fucose analogue: The synthesis of the racemic aminofuranofucitol 3 from sorbic alcohol by nitroso-Diels-Alder reaction. This 'all-cis-pyrrolidine', with all substituents occupying a cis position, has been determined as a potent inhibitor of α-L-fucosidase and a moderate inhibitor of α- and ß-D-galactosidase. The good recognition of this fucose moiety analogue by specific enzymes is thus confirmed. The C-anomeric bond in this particular structure is in the ß-position and makes this compound an interesting candidate for further chemical modifications. Influence of the methyl and hydroxymethyl groups on the inhibition potency is discussed.