Non-active Compounds Research Articles

Experimental determination and calculations of redox potential descriptors of compounds directed against retroviral zinc fingers: Implications for rational drug design.

A diverse set of electrophilic compounds that react with cysteine thiolates in retroviral nucleocapsid (NC) proteins and abolish virus infectivity has been identified. Although different in chemical composition, these compounds are all oxidizing agents that lead to the ejection of Zn(II) ions bound to conserved structural motifs (zinc fingers) present in retroviral NC proteins. The reactivity of a congeneric series of aromatic disulfides toward the NC protein of the human immunodeficiency virus type 1 (HIV-1), NCp7, has been characterized by HPLC separation of starting reagents from reaction products. We calculated the absolute redox potentials of these compounds in the gas phase and in aqueous solvent, using a density functional theory method and a continuum solvation model. Pulsed polarography experiments were performed and showed a direct correlation between calculated and experimentally determined redox propensities. A dependence between protein reactivity and redox potential for a specific compound was shown: Reaction with NCp7 did not take place below a threshold value of redox potential. This relationship permits the distinction between active and nonactive compounds targeted against NCp7, and provides a theoretical basis for a scale of reactivity with retroviral zinc fingers. Our results indicate that electrophilic agents with adequate thiophilicity to react with retroviral NC fingers can now be designed using known or calculated electrochemical properties. This may assist in the design of antiretroviral compounds with greater specificity for NC protein. Such electrophilic agents can be used in retrovirus inactivation with the intent of preparing a whole-killed virus vaccine formulation that exhibits unaffected surface antigenic properties.

Evolution of reproductive strategies in the sexually deceptive orchid Ophrys sphegodes: how does flower-specific variation of odor signals influence reproductive success?

The orchid Ophrys sphegodes Miller is pollinated by sexually excited males of the solitary bee Andrena nigroaenea, which are lured to the flowers by visual cues and volatile semiochemicals. In O. sphegodes, visits by pollinators are rare. Because of this low frequency of pollination, one would expect the evolution of strategies that increase the chance that males will visit more than one flower on the same plant; this would increase the number of pollination events on a plant and therefore the number of seeds produced. Using gas chromatography-mass spectrometry (GC-MS) analyses, we identified more than 100 compounds in the odor bouquets of labellum extracts from O. sphegodes; 24 compounds were found to be biologically active in male olfactory receptors based on gas chromatography with electroantennographic detection (GC-EAD). Gas chromatography (GC) analyses of odors from individual flowers showed less intraspecific variation in the odor bouquets of the biologically active compounds as compared to nonactive compounds. This can be explained by a higher selective pressure on the pollinator-attracting communication signal. Furthermore, we found a characteristic variation in the GC-EAD active esters and aldehydes among flowers of different stem positions within an inflorescence and in the n-alkanes and n-alkenes among plants from different populations. In our behavioral field tests, we showed that male bees learn the odor bouquets of individual flowers during mating attempts and recognize them in later encounters. Bees thereby avoid trying to mate with flowers they have visited previously, but do not avoid other flowers either of a different or the same plant. By varying the relative proportions of saturated esters and aldehydes between flowers of different stem positions, we demonstrated that a plant may take advantage of the learning abilities of the pollinators and influence flower visitation behavior. Sixty-seven percent of the males that visited one flower in an inflorescence returned to visit a second flower of the same inflorescence. However, geitonogamy is prevented and the likelihood of cross-fertilization is enhanced by the time required for the pollinium deposited on the pollinator to complete its bending movement, which is necessary for pollination to occur. Cross-fertilization is furthermore enhanced by the high degree of odor variation between plants. This variation minimizes learned avoidance of the flowers and increases the likelihood that a given pollinator would visit several to many different plants within a population.

Bioactive compounds from Celaenodendron mexicanum.

Bioactivity-directed fractionation of the CHCl3-MeOH extract of the leaves of Celaenodendron mexicanum by means of the brine shrimp lethality test and chromatographic techniques led to the isolation of three carboxylic acid triterpenes, the new tirucalla-type triterpene, 3 alpha-hydroxytirucalla-7,24Z-dien-26-oic acid, 3-oxotirucalla-7,24Z-dien-26-oic acid, and epi-oleanolic acid, and three biflavonoids amentoflavone, podocarpusflavone A, and podocarpusflavone B. Four non-active compounds friedelin, maytensifolin B, 3 beta-hydroxyfriedelan-16-one, and celaenodendrolide were also obtained. epi-Oleanolic acid was the most active against brine shrimps with LC50 value of 23.3 microM. In addition, all isolates were tested for in vitro antiprotozoal and cytotoxic activities. 3-Oxotirucalla-7,24Z-dien-26-oic acid and epi-oleanolic acid showed the highest activity against Leishmania donovani promastigotes with IC50 values of 13.7 and 18.8 microM, respectively. Only 3-oxotirucalla-7,24Z-dien-26-oic acid showed activity against Trypanosoma brucei brucei bloodstream forms with IC50 value of 16.8 microM.

Luteolin, a compound with adenosine A(1) receptor-binding activity, and chromone and dihydronaphthalenone constituents from Senna siamea.

Activity-guided fractionation led to the isolation of luteolin (1) from the leaves of Senna siamea (syn. Cassia siamea). This compound was found to be an antagonist at the adenosine A(1) receptor with a K(i) value in the low micromolar range. Four additional nonactive compounds (2-5) were also isolated, and their structures were elucidated. One compound was identified as cassia chromone (5-acetonyl-7-hydroxy-2-methylchromone) (2). Three other compounds are new, and they were identified as 5-acetonyl-7-hydroxy-2-hydroxymethyl-chromone (3), 4-(trans)-acetyl-3,6,8-trihydroxy-3-methyldihydronaphthalenone (4), and 4-(cis)-acetyl-3,6,8-trihydroxy-3-methyldihydronaphthalenone (5).

EVOLUTION OF REPRODUCTIVE STRATEGIES IN THE SEXUALLY DECEPTIVE ORCHID OPHRYS SPHEGODES: HOW DOES FLOWER-SPECIFIC VARIATION OF ODOR SIGNALS INFLUENCE REPRODUCTIVE SUCCESS?

The orchid Ophrys sphegodes Miller is pollinated by sexually excited males of the solitary bee Andrena nigroaenea, which are lured to the flowers by visual cues and volatile semiochemicals. In O. sphegodes, visits by pollinators are rare. Because of this low frequency of pollination, one would expect the evolution of strategies that increase the chance that males will visit more than one flower on the same plant; this would increase the number of pollination events on a plant and therefore the number of seeds produced. Using gas chromatography-mass spectrometry (GC-MS) analyses, we identified more than 100 compounds in the odor bouquets of labellum extracts from O. sphegodes; 24 compounds were found to be biologically active in male olfactory receptors based on gas chromatography with electroantennographic detection (GC-EAD). Gas chromatography (GC) analyses of odors from individual flowers showed less intraspecific variation in the odor bouquets of the biologically active compounds as compared to nonactive compounds. This can be explained by a higher selective pressure on the pollinator-attracting communication signal. Furthermore, we found a characteristic variation in the GC-EAD active esters and aldehydes among flowers of different stem positions within an inflorescence and in the n-alkanes and n-alkenes among plants from different populations. In our behavioral field tests, we showed that male bees learn the odor bouquets of individual flowers during mating attempts and recognize them in later encounters. Bees thereby avoid trying to mate with flowers they have visited previously, but do not avoid other flowers either of a different or the same plant. By varying the relative proportions of saturated esters and aldehydes between flowers of different stem positions, we demonstrated that a plant may take advantage of the learning abilities of the pollinators and influence flower visitation behavior. Sixty-seven percent of the males that visited one flower in an inflorescence returned to visit a second flower of the same inflorescence. However, geitonogamy is prevented and the likelihood of cross-fertilization is enhanced by the time required for the pollinium deposited on the pollinator to complete its bending movement, which is necessary for pollination to occur. Cross-fertilization is furthermore enhanced by the high degree of odor variation between plants. This variation minimizes learned avoidance of the flowers and increases the likelihood that a given pollinator would visit several to many different plants within a population.

New developments in a hazard identification algorithm for hormone receptor ligands

Recently we described the Common REactivity PAttern (COREPA) technique to screen data sets of diverse structures for their ability to serve as ligands for steroid hormone receptors [1]. The approach identifies and quantifies similar global and local stereoelectronic characteristics associated with active ligands through a comparison of energeticallyreasonable conformer distributions for selected descriptors. For each stereoelectronic descriptor selected, discrete conformer distributions from a training set of ligands are evaluated and parameter ranges common for conformers from all the chemicals in the training set are identified. The use of discrete partitions of parameter ranges to define common reactivity patterns can, however, influence the outcome of the algorithm. To address this limitation, the original method has been extended by approximating continuous conformer distributions as probability distributions. The COREPA-Continuous (COREPA-C) algorithm assesses the common reactivity pattern of biologicallysimilar molecules in terms of a product of probability distributions, rather than a collection of common population ranges determined by examination of discrete partitions of a distribution. To illustrate the algorithm, common reactivity patterns based on interatomic distance and charge on heteroatoms were developed and evaluated using a set of 28 androgen receptor ligands. Notable attributes of the COREPA-C algorithm include flexibility in establishing stereoelectronic descriptor criteria for identifying active and nonactive compounds and the ability to quantify threedimensional chemical similarity without the need to predetermine a toxicophore or align compounds(s) to a lead ligand.

Pharmacokinetics of Lercanidipine in Animals

[14C]Lercanidipine hydrochloride was administered to rats, p.o. at 3 mg/kg in single and repeated dose, and dogs at 0.5 mg/kg in single dose, to investigate the distribution, biliary excretion, recycling, and elimination of the drug. Radioactivity was rapidly and extensively distributed to organs and tissues in rats and dogs, the levels being higher than in plasma 30 min (rats) and 2 h (dogs) after administration. Decay of radioactivity from the tissues was relatively slower than that in plasma, and the liver appears to be the target organ in both species. After repeated administration to rats, unlike in the single dose study, radioactivity was detectable until 96 h post dose in aorta and cava vein organs, largely investigated in pharmacologic in vitro studies. No difference between radioactivity levels in pigmented and non-pigmented skin was observed in dogs. Biliary excretion plays an important role in the disposition of lercanidipine in rats and dogs. The radioactivity excreted into the rat bile after single [14C]lercanidipine administration is represented only by metabolites and accounts for 30% of the dose. About 20% of this radioactivity is reabsorbed. Thin-layer chromatography comparison of the metabolites in bile with reference standards shows that lercanidipine biotransformation involves mainly the oxidation of the dihydropyridine ring and affords to nonactive compounds.

Conformational study of 2-phenylbenzothiazine part of SA2995, a Ca 2+ antagonist having a benzothiazine skeleton, and structure-activity relationships

Nuclear magnetic resonance (NMR) studies were carried out for the title compound ((±)-3,4-dihydro-2-[5-methoxy-2-[3-[ N-methyl- N-[2-(3,4-methy ( 1a; R = H) and its 2-substituted analogs ( 1b; R = OCH 3, 1c; R = SCH 3, 1d; R = CH 3, 1e; R = i-C 3H 7) which had Ca 2+ activities. Conformational analysis using the model compounds of the 2-phenylbenzothiazine (2-PBT) part of 1 by semiempirical molecular orbital method agreed with the NMR behavior. Two local minimum conformations, having different rotational angles (θ1) of the 2-phenyl ring, were suggested for biologically active 1a–1d. The molar fractional ratios, including the conformations within a particular θ1 range that contained each global minimum conformation, were found to correlate well with the activities. In the same θ1 range, any stable conformation was not indicated for non-active compound 1e. From these results, the active conformation for the 2-PBT part of 1 was suggested to be similar to the global minimum conformation indicated for the most potent 1a.

Electrophysiological and field activity of halogenated analogs of (E,E)-8,10-dodecadien-1-ol, the main pheromone component, in codling moth (Cydia pomonella L.)

Pest monitoring and control of the codling moth,Cydia pomonella L., have been developed using the main pheromone component of this species, (E,E)-8,10-dodecadienol (codlemone). However, the activity of codlemone is not satisfactory for pest control by mating disruption. Thus, we have synthesized halogenated analogs of codlemone to see if they could be used as new agents for pest control of the codling moth. Their biological activity was measured by electrophysiological techniques. In EAG screening, codlemone was the most active compound. F(10,11)-codlemone [(E,E)-10,11-difluoro-8,10-dodecadienol] and Cl-codlemone [(E,E)-11-chloro-8,10-undecadienol] elicited significant EAG responses, F(10,11)-codlemone triggering responses not significantly different from responses to codlemone. EAG cross-adaptation experiments and single sensillum recordings revealed that these compounds were detected by the same receptor neuron type as codlemone. No competitive inhibition with codlemone was observed from nonactive compounds. In field trapping, F(10,11)-codlemone and Cl-codlemone were more attractive to male codling moths than codlemone itself. Possible explanations of this activity are discussed.

Estrogen-stimulated glucuronidation of dihydrotestosterone in MCF-7 human breast cancer cells

The non-aromatizable androgen dihydrotestosterone (DHT) has been shown to exert a potent inhibitory effect on the proliferation of some human breast cancer cell lines. DHT, however, has little or no significant inhibition on MCF-7 cell proliferation in either the presence or absence of estradiol (E 2). Since the metabolism of DHT into non-active compounds may be responsible for the observed lack of androgenic effect in this cell line, we have investigated the metabolic fate of labeled DHT in MCF-7 cells. A time course incubation was performed with 1 nM [ 3H]DHT and analysis of the various metabolites formed revealed a time-dependent increase in glucuronidated steroids which was stimulated more than 4-fold by 0.1 nM E 2. The major glucuronidated steroid was androstane-3α, 17β-diol in both control and E 2-stimulated cells, comprising 22 ± 1.2% and 30 ± 0.6% of the total radioactivity in the medium, respectively. Other steroid glucuronides observed included DHT, androstane-3β, 17β-diol, and androsterone, all of which were elevated in the E 2-treated cells relative to control values. The present data show that E 2 exerts a stimulatory effect on the glucuronidation of androgens and their metabolites in the estrogen-dependent breast cancer celll line MCF-7. Since glucuronidation is an effective means of cellular elimination of active steroids, such a pathway may be considered as a possible site of regulation of breast cancer cell growth by hormones.

The defensive secretion of omaliinae and proteininae (Coleoptera: Staphylinidae): Its chemistry, biological and taxonomic significance

The chemistry of the abdominal defensive secretions of 24 Omaliinae and Proteininae species (Coleoptera: Staphylinidae) was analysed by GC-MS. From the 98 detected constituents, 46 compounds could be identified as acids, aldehydes, ketoaldehydes, ketones, alcohols, esters, terpenes, aromatic compounds and hydrocarbons. Various esters, benzonitrile and phenoxyethanol were recorded for the first time from insect defensive glands. Two main types of defensive mixtures that partly resemble natural products from heteropteran thoracic glands were found among the species examined: acids, corresponding aldehydes and alcohols and the appropriate esters (I: Omalium, Lathrimaeum, Phyllodrepa, Eusphalerum, Phleonomus, Proteinus) whereas a gradual replacement of esters by a hydrocarbon was observed within two genera (II: several Eusphalerum species, Anthophagus). Further secretion-types were represented by a ketone in admixture with a hydrocarbon ( Lesteva); the genus Megarthrus is characterized by a very odd defensive secretion covering aromatics, an acetate and an aldehyde. The genus Proteinus (secretion-type I) additionally contains 4-oxo-2-hexenal as the main compound in its defensive secretion, Omalium rivulare further sequesters terpenes. The topical irritancy of several constituents was tested as single-compound and as mixtures by using larvae of Calliphora vomitoria (L.) as targets. Only aldehydes, ketones or aromatics but not acids showed a topical irritancy when tested alone; however, the activity is significantly improved when numerous sometimes non-active compounds are mixed and can therefore act synergistically. Finally, composition and chemical patterns of the defensive secretion of 24 species were compared with the actual taxonomic system of Omaliinae and Proteininae. Possible new taxonomic ideas based on chemical similarities were discussed.

Calculations of the conformational properties of acyclonucleosides: Part 2. Comparison of active and nonactive compounds

Two related molecules from the acyclic nucleoside family 9-(1,3-dihydroxy-2-propoxymethyl) guanine (DHPG) and 9-(1,5-dihydro-4-hydroxymethyl-3-oxapentyl-2- [R])guanine (2′, 3′- secoG) have been compared by means of force field conformational analysis. They are respectively active and nonactive analogs of the antivirial compound 9-((2-hydroxyethoxy)methyl)guanine (ACG). As in the case of ACG many local minima are found for both molecules, indicating their great flexibility. For all three molecules conformations similar to those occurring in cyclic nucleosides have energies from 3 to 7 kcal mol −1 above the most stable minima.

Mutagenicity of some substituted 1-phenyl-3,3-dimethyltriazenes: II. Chromosomal aberrations in human peripheral lymphocytes in vitro

The chromosome-breaking activity of four 1-(phenyl)-3,3-dimethyltriazenes was tested in vitro on human peripheral blood lymphocytes using S9 mix as a metabolic activation system. 1-(4-Nitrophenyl)-3,3-dimethyltriazene was the most active compound. The difference in the frequency of chromosomal aberrations in a test with and without metabolic activation was significant at the 1% level of significance. The lowest frequency of chromosomal aberrations was induced by 1-(4-methylphenyl)-3,3-dimethyltriazene which, under the conditions of this experiment, is the least stable and probably rapidly degraded to non-active compounds. The chromosomal aberrations were also induced by 1-(4-chlorophenyl)-3,3-dimethyltriazene and 1-(4-bromophenyl)-3,3-dimethyltriazene, this activity was unrelated to metabolic activation.

The problem of adsorption on silicagel in a liquid scintillation radiometry of14C labelled compounds

By means of liquid scintillation spectrometry we investigated the counting efficiency of the samples containing toluene solution of scintillator (PPO, butyl-PBD, PT) and 1-methyl[2−14C]imidazolidinone-2 adsorbed on the silicagel, depending on concentration of scintillator, mass of radioactive compound, and mass of another nonactive compound introduced to samples as an impurity. For the sake of comparison the efficiency of counting homogeneous samples and the ones with Ba14CO3 deposit was determined. It was found, that the efficiency of detection of a radioactive compound adsorbed on the silicagel is conditioned by composition of adsorptive layer on the support surface.

Teratogenic compounds in Veratrum californicum (Durand) IX. Structure-activity relation.

AbstractThe structures and configurations of three naturally occurring steroidal alkaloid teratogens from Veratrum californicum that induce cyclopia in sheep have been elucidated. The probable teratogenic structural requirements were examined in light of known structural and configurational information on active and nonactive compounds. Methods are proposed that will enable elucidation of the precise structural requirements for this teratogenic effect.