Chemical Constituents and Anticancer Activities of the Extracts from Phlomis × commixta Rech. f. (P. cretica × P. lanata)

The present work is the first report on the ingredients of the P. × commixta hybrid, a plant of the genus Phlomis. So far, thirty substances have been isolated by various chromatographic techniques and identified by spectroscopic methods, such as UV/Vis, NMR, GC-MS and LC-MS. The compounds are classified as flavonoids: naringenin, eriodyctiol, eriodyctiol-7-O-β-D-glucoside, luteolin, luteolin-7-O-β-D-glucoside, apigenin, apigenin-7-O-β-D-glucoside, diosmetin-7-O-β-D-glucoside, quercetin, hesperetin and quercetin-3-O-β-D-glucoside; phenylpropanoids: martynoside, verbascoside, forsythoside B, echinacoside and allysonoside; chromene: 5,7-dihydroxychromone; phenolic acids: caffeic acid, p-hydroxybenzoic acid, chlorogenic acid, chlorogenic acid methyl ester, gallic acid, p-coumaric acid and vanillic acid; aliphatic hydrocarbon: docos-1-ene; steroids: brassicasterol and stigmasterol; a glucoside of allylic alcohol, 3-O-β-D-apiofuranosyl-(1→6)-O-β-D-glucopyranosyl-oct-1-ene-3-ol, was fully characterized as a natural product for the first time. Two tyrosol esters were also isolated: tyrosol lignocerate and tyrosol methyl ether palmitate, the latter one being isolated as a natural product for the first time. Moreover, the biological activities of the extracts from the different polarities of the roots, leaves and flowers were estimated for their cytotoxic potency. All root extracts tested showed a high cytotoxic activity against the Hep2c and RD cell lines.

Biological Activities of Ceratonia siliqua Pod and Seed Extracts: A Comparative Analysis of Two Cretan Cultivars

Ceratonia siliqua L., commonly known as the carob tree, appears in most Mediterranean countries, often cultivated for the collection of its fruits to be used as food for humans and animals. This study was aimed at the phytochemical characterization of two common Cretan C. siliqua cultivars and the biological evaluation of deseeded pod and seed extracts regarding their putative use in cosmetics. Gas and liquid chromatographic techniques were used to assess their essential oil, fatty acid, and carbohydrate profiles. Cell-free assays, including free-radical scavenging; the inhibition of tyrosinase and collagenase; the blocking of advanced glycation end product (AGE) formation; along with assays in human skin fibroblast cultures, i.e., reactive oxygen species suppression, glutathione stimulation, and protection from oxidative stress and from ultraviolet (UVB) radiation, were also used. Extracts from both cultivars were found to possess antioxidant capacity, tyrosinase- and collagenase-inhibitory activities, an ability to block glucose-induced AGEs, and in certain cases, UVB absorbance and photoprotective activities. Seed extracts were in general more active, while the use of 30% aqueous methanol seemed to be more efficient than n-hexane for extraction. Serial partition of the most active extracts resulted in fractions with enriched biological activities. These properties make Cretan carob extracts and their fractions suitable candidates for use in cosmetics.

The Synthetic Microneurotrophin BNN27 Affects Retinal Function in Rats With Streptozotocin-Induced Diabetes

BNN27, a C17-spiroepoxy derivative of DHEA, was shown to have antiapoptotic properties via mechanisms involving the nerve growth factor receptors (tropomyosin-related kinase A [TrkA]/neurotrophin receptor p75 [p75^NTR]). In this study, we examined the effects of BNN27 on neural/glial cell function, apoptosis, and inflammation in the experimental rat streptozotocin (STZ) model of diabetic retinopathy (DR). The ability of BNN27 to activate the TrkA receptor and regulate p75^NTR expression was investigated. BNN27 (2,10, and 50 mg/kg i.p. for 7 days) administration 4 weeks post-STZ injection (paradigm A) reversed the diabetes-induced glial activation and loss of function of amacrine cells (brain nitric oxide synthetase/tyrosine hydroxylase expression) and ganglion cell axons via a TrkA receptor (TrkAR)-dependent mechanism. BNN27 activated/phosphorylated the TrkA^Y490 residue in the absence but not the presence of TrkAR inhibitor and abolished the diabetes-induced increase in p75^NTR expression. However, it had no effect on retinal cell death (TUNEL⁺ cells). A similar result was observed when BNN27 (10 mg/kg i.p.) was administered at the onset of diabetes, every other day for 4 weeks (paradigm B). However, BNN27 decreased the activation of caspase-3 in both paradigms. Finally, BNN27 reduced the proinflammatory (TNFα and IL-1β) and increased the anti-inflammatory (IL-10 and IL-4) cytokine levels. These findings suggest that BNN27 has the pharmacological profile of a therapeutic for DR, since it targets both the neurodegenerative and inflammatory components of the disease.

Use of costic acid, a natural extract from Dittrichia viscosa, for the control of Varroa destructor, a parasite of the European honey bee

Costic acid has been isolated from the plant Dittrichia viscosa and its efficacy against Varroa destructor, a parasite of Apis mellifera, the European honey bee, has been studied. Costic acid exhibited potent in vivo acaricidal activity against the parasite. Initial experiments showed that the compound is not toxic for human umbilical vein endothelial cells (HUVEC) at concentrations of up to 230 micromolar (μM), indicating that costic acid could be used as a safe, low-cost and efficient agent for controlling varroosis in honey bee colonies.

Chemical and genetic characterization of Phlomis species and wild hybrids in Crete

The genus Phlomis is represented in the island of Crete (Greece, Eastern Mediterranean) by three species Phlomis cretica C. Presl., Phlomis fruticosa L., the island endemic Phlomis lanata Willd. and three hybrids Phlomis x cytherea Rech.f. (P. cretica x P. fruticosa), Phlomis x commixta Rech.f. (P. cretica x P. lanata) and Phlomis x sieberi Vierh. (P. fruticosa x P. lanata). This work describes (a) the profile of hybrids and parental species concerning their volatile compounds, (b) the suitability of ribosomal nuclear (ITS region), chloroplast (trnH-psbA), and AFLP markers to identify hybrids and (c) their competence to characterize the different chemotypes of both hybrids and their parental species. The cluster analysis and PCA constructed from chemical data (volatile oils) suggest that there are three groups of taxa. Group IA includes P. cretica and P. fruticosa, group IB includes P. x cytherea, whereas group II consists of P. x commixta, P. x sieberi and P. lanata. Volatile compounds detected only in the hybrids P. x sieberi and P. x commixta correspond to the 3% of the total compounds, value that is much higher in P. x cytherea (21%). Neighbor-joining, statistical parsimony analysis and the observations drawn from ribotypes spectrum of ITS markers divided Phlomis species in two groups, P. lanata and the complex P. cretica/P. fruticosa. In contrast to the ITS region, the plastid DNA marker follows a geographically related pattern. Neighbor-Net, PCA and Bayesian assignment analysis performed for AFLP markers separated the genotypes into three groups corresponding to populations of P. cretica, P. fruticosa, and P. lanata, respectively, while populations of P. x commixta, P. x cytherea, and P. x sieberi presented admixed ancestry. Most of the P. x cytherea samples were identified as F1 hybrids by Bayesian assignment test, while those of P. x commixta and P. x sieberi were identified as F2 hybrids. Overall, high chemical differentiation is revealed in one of the three hybrids, which is likely related with niche variation. Moreover, molecular markers show potential to identify Phlomis taxa.

Reporting effectiveness of an extract of three traditional Cretan herbs on upper respiratory tract infection: results from a double-blind randomized controlled trial

ETHNOPHARMACOLOGICAL RELEVANCE

Observations from the island of Crete, Greece suggest that infusions of traditional Cretan aromatic plants, well known for their ethnopharmacological use in Eastern Mediterranean region and Near East, could be effective in the prevention and treatment of upper respiratory tract infections, including viral-induced infections. The aim of this study was to report the effectiveness of an essential-oil extract of three Cretan aromatic plants in the treatment of cases with an upper respiratory tract infection.

MATERIALS AND METHODS

A double blind randomized controlled trial was implemented between October 2013 and February 2014. An essential-oil extract of Cretan aromatic plants in olive oil (total volume of 15ml of essential oil per litre of olive oil) was administered as 0.5ml soft gel capsules, twice a day, for 7 days. Placebo treatment was 0.5ml olive oil in soft gel capsules. Eligible patients were those presenting for clinical examination in the selected setting with signs and symptoms of upper respiratory tract infection that had begun within the previous 24 hours. Real-Time Polymerase Chain Reaction (PCR) was used for the detection of respiratory viruses. The primary outcome was the severity and duration of symptoms of upper respiratory tract infection, assessed using the Wisconsin Upper Respiratory System Survey (WURSS-21) questionnaire. A secondary outcome of interest was the change in C-reactive protein (CRP) status.

RESULTS

One hundred and five patients completed the study: 51 in the placebo group, and 54 in the intervention (treated) group. Baseline characteristics were similar in the two groups. No statistically significant differences were found in symptom duration or severity between the two groups, although small and clinically favorable effects were observed. When the analysis was restricted to subjects with a laboratory-documented viral infection, the percentage of patients with cessation of symptoms after 6 days of treatment was 91% in the intervention group and 70% in the control group (p=0.089). At baseline, one third of the patients in each group had elevated CRP levels. At follow-up, the respective proportions were 0% in the intervention group and 15% in the placebo group (p=0.121). The data were also in a favorable direction when 50% and 80% symptom reduction points were considered for specific virus types.

CONCLUSIONS

Compared with placebo the essential-oil extract of three Cretan aromatic plants provided no detectable statistically significant benefit or harm in the patients with upper respiratory illness, although descriptive differences were identified in favorable direction mainly in the virus-positive population.

ICPBCZin: a red emitting ratiometric fluorescent indicator with nanomolar affinity for Zn2+ ions

A new fluorescent Zn2+ indicator, namely, ICPBCZin was synthesized and the spectral profile of its free and Zn2+ bound forms was studied. The newly synthesized zinc indicator incorporates as chromophore the chromeno [3',2':3,4]pyrido[1,2a] [1,3]benzimidazole moiety and belongs to the dicarboxylate-type of zinc probes. The compound is excited with visible light, exhibits high selectivity for zinc in the presence of calcium and other common biological ions, and its Zn2+ dissociation constant is 4.0 nM. Fluorescence spectra studies of ICPBCZin indicated a clear shift in its emission wavelength maxima upon Zn2+ binding, as it belongs to the class of Photoinduced Charge Transfer (PCT) indicators, along with changes in fluorescence intensity that enable the compound to be used as a ratiometric, visible-excitable Zn2+ probe.

Anti-inflammatory and antioxidant activity of coumarins designed as potential fluorescent zinc sensors

A series of coumarin analogs, designed and synthesised as potential fluorescent zinc probes were evaluated for their biological activity as anti-inflammatory and antioxidant agents. The effect of the synthesised compounds on inflammation, using the carrageenin-induced rat paw oedema model, was studied. In general, the compounds were found to be potent anti-inflammatory agents (26.5-64%). Compound 5 was found to interact significantly with 1,1-diphenyl-2-picryl-hydrazyl stable free radical (DPPH) whereas the remainder were inactive in this assay. The compounds inhibit in general the soybean lipoxygenase and scavenge superoxide anion radicals. The anti-inflammatory activity seems to be connected with their reducing activity. Their RM values were determined as an expression of their lipophilicity. Theoretical calculations of their lipophilicity as clog P were performed indicating that only a poor relationship exists between their lipophilicity and anti-inflammatory activity.

Quercetin exhibits a specific fluorescence in cellular milieu: a valuable tool for the study of its intracellular distribution

The elaboration of novel techniques for flavonoid intracellular tracing would elucidate the compounds' absorption and bioavailability and assist molecular and pharmacological approaches, as they are promising candidates for drug development. This study exploited the properties of quercetin (3,3',4',5,7-pentahydroxyflavone), found in high concentrations in the majority of edible plants. Through the use of UV-vis spectroscopy, confocal microscopy, and HPLC-ESI-MS, native quercetin, at physiologically relevant concentrations, was found to exhibit a specific fluorescence (488 nmex/500-540 nmem) upon internalization. This fluorescence shift is due to a non-covalent binding to intracellular targets (probably proteins) and compatible with the settings applied in confocal microscopy. This property provides a valuable, selective alternative technique for quercetin tracing in cellular systems, permitting the quantitative evaluation of its transit at pharmacologically relevant concentrations and the validation of a number of already described molecular functions.

ICPBC and C12-ICPBC: Two new red emitting, fluorescent Ca2+ indicators excited with visible light

Two new, visible-excited and red-emitting fluorescent Ca(2+) indicators were synthesized and the spectral profiles of their free and Ca(2+) bound forms were studied. The fluorescent properties of these probes are due to the extended conjugation of the chromeno[3',2':3,4]pyrido[1,2a][1,3]benzimidazole chromophore incorporated in their BAPTA-type, Ca(2+) chelating structure. The compounds, namely ICPBC and its N-dodecyl analog C12-ICPBC exhibit Ca(2+) dissociation constants of 7.7 and 18.0 microM, respectively. The fluorescence spectra of the probes showed a clear shift in excitation wavelength maxima upon Ca(2+) binding along with a large Stokes shift and changes in fluorescence intensity, indicating their potential use as Ca(2+) indicators. The ability of ICPBC to trace high calcium spikes was tested in the human HepG2 cell line with positive results.

Composition and insect attracting activity of the essential oil of Rosmarinus officinalis

The essential oil and a number of extracts of Rosmarinus officinalis L. in solvents of increasing polarity were isolated, and their components identified and tested as pest control agents. Ethanol and acetone extracts attract grape berry moth Lobesia botrana. However, none of the extracts had a significant effect on western flower thrips Frankliniella occidentalis, which is attracted by 1,8-cineole, a major essential oil component.

Correction of the structure of a new sesquiterpene from Cistus creticus ssp. creticus

In an attempt to identify the structure of a sesquiterpene from Cistus creticus ssp. creticus proposed in the literature as 1,1,4a,6-tetramethyl-5-methylene-1,2,3,4,4alpha,5,8,8alpha-octahydronaphthalene, the synthesis of its cis isomer 2 was carried out in 11 steps and 9.5% yield. Comparison of the spectra of 2 and those reported earlier for the synthetic trans isomer 1 with the spectral profile of the isolated natural product indicated that the latter was not compatible with either 1 or 2. The correct structure was assigned, by detailed spectroscopic analysis of the natural product, as 6-isopropenyl-4,4a-dimethyl-1,2,3,4,4a,5,6,7-octahydronaphthalene (3).

The Coumarin Moiety as Chromophore of Fluorescent Ion Indicators in Biological Systems

Fluorescent probes have evolved into an extremely useful tool for the detection of ions in biological systems. The design of ion indicators is based in the proper choice of the ion chelating group as well as the chromophore moiety. The chromophores of choice should fulfill a number of requirements concerning the photostability of the group, the range of the excitation and emission wavelengths of the indicators, the Stokes shift, the fluorescence quantum yield, the excitation and/or emission wavelength shift upon coordination of the probe with its target ion, the lipophilicity of the indicators, and their possible cell toxicity. Coumarin and its analogues have been extensively used in ion detection by incorporation of the coumarin chromophore in the larger indicator framework. Coumarins fulfill all the aforementioned requirements since they are relatively photostable and their excitation and emission maxima, in many cases, are long enough to minimise "background" fluorescence of cellular components, tissues and biological fluids. They exhibit Stokes shifts large enough to avoid significant overlap of the excitation and emission spectra, their fluorescence quantum yields allow for ion detection at low indicator concentrations, and they can be introduced to cells either by microinjection or as membrane permeable derivatives without causing cell death. Synthetic approaches, aiming at the optimisation of indicator properties, have extended the conjugated coumarin system either by introduction of substituents or by expansion of the heterocyclic system. In this review, the basic rationale for the selection of the particular coumarin analogues is analysed, synthetic pathways leading to the desired structures are presented, and properties and relative advantages in the use of these probes are described.

Near-membrane iminocoumarin-based low affinity fluorescent Ca(2+) indicators

Two new potential near-membrane iminocoumarin-based fluorescent Ca(2+) indicators were synthesized and the spectral profiles of their free and Ca(2+) bound forms were studied. The probes incorporate in their BAPTA-related structures, the 3-(benzimidazolyl)iminocoumarin or the 3-(benzothiazolyl)iminocoumarin moiety, substituted at the imino nitrogen with an n-dodecyl lipophilic chain. The compounds are excited with visible light and have Ca(2+) dissociation constant values of 5.50 and 4.49 microM, respectively, the highest reported to date in the literature. Fluorescence spectra studies indicated a clear shift in their excitation wavelength maxima upon Ca(2+) binding along with changes in fluorescence intensity that enable the compounds to be used as ratiometric near-membrane, low Ca(2+) affinity probes.

Polycarboxylate fluorescent indicators as ion concentration probes in biological systems

A large number of techniques have been applied to monitor the function of free metal ions in biological systems. Fluorescent ion probes have evolved into an extremely useful tool for contemporary experimentalists. Polycarboxylate indicators are widely used in the determination of metal ion concentrations, especially due to their cell membrane permeability. The design of these probes required detailed knowledge in related fields of medicine, biology, and chemistry, and their preparation demanded the expertise of organic synthesis. In this review, the basic rationale for the selection of particular chemical structures are analyzed, synthetic pathways leading to the desired structures are presented, often via a retrosynthetic approach, and properties and relative advantages of the use of these probes are described. References to specific applications are limited, given the large number of reviews on related subjects. Topics such as those related to dextran conjugates that are broad enough to be the subject of a different review are not included, and leakage resistance and near-membrane probes are mentioned briefly in separate sections, although these are chemically similar to typical polycarboxylate dyes. While reference to topics mentioned in related reviews is unavoidable, presentation of material in this review is from the point of view of a medicinal chemist rather than that of the many experts using these pioneering techniques.

Iminocoumarin-based low affinity fluorescent Ca2+ indicators excited with visible light

A series of iminocoumarin-based fluorescent Ca2+ indicators were synthesized and the spectral profiles of their free and Ca2+ bound forms were studied. The newly-synthesized compounds incorporate the Ca2+ chelating structure of BAPTA. The chromophore moieties are iminocoumarins substituted at the 3-position with benzothiazolyl, benzoxazolyl and benzimidazolyl groups. These compounds are excited with visible light and their Ca2+ dissociation constants range from 5.4 to 27.5 microM. Fluorescence spectra studies of these probes indicated a clear shift in their excitation wavelength maxima upon Ca2+ binding along with changes in fluorescence intensity that enable the compounds to be used as low Ca2+ affinity, visible excitable probes.

Cis- and trans-N-benzyl-octahydrobenzo[g]quinolines. Adrenergic and dopaminergic activity studies

In vitro assays on a series of cis- and trans-octahydrobenzo[g]quinolines indicated an unusual trend of affinities at the dopaminergic receptors and alpha adrenoceptors. The trans N-benzyl analogues exhibited affinity at the alpha2 as well as the D1-like receptors whereas their N-unsubstituted congeners showed a distinct preference for the alpha2 adrenoceptor. Enhanced activity for the alpha2 receptors was also exhibited by the cis N-benzylated isomers. These observations are interpreted by theoretical calculations.

N-(Iodopropenyl)-octahydrobenzo[f]- and -[g]quinolines: synthesis and adrenergic and dopaminergic activity studies

A series of N-(iodopropenyl)-octahydrobenzo[f]- and -[g]quinolines was synthesized and assayed in vitro for their dopaminergic and alpha-adrenergic activity. Structure-activity relationship (SAR) analysis revealed that the tested benzoquinolines exhibited activity at the D1 rather than the D2 receptor sites in contrast to the D2 receptor subfamily activity reported for their aminotetralin congeners. N-Iodopropenyl substitution was apparently a decisive factor for D1 activity independent of ring substitution pattern. Considering the structural factors influencing alpha-adrenergic activity, in a general trend, N-iodopropenyl analogues were alpha1-active, with the ring-hydroxylated congeners exhibiting the highest affinity. Affinity to the alpha2 receptor was even higher with no detectable trend of SAR. However, a combination of the linear arrangement of the [g]-ring system, combined with the ring hydroxyl and the N-iodopropenyl substitution in compound 5c, resulted in a significant enhancement of alpha2 activity in this series as demonstrated by an IC50 value of 0.5 nM. A new synthetic approach to the [g]benzoquinoline system is also described.

Detection of cardiovascular calcified deposits via tetracarboxylate ion dye (BTC) probing and laser-induced fluorescence spectroscopy

In order to develop a reliable, laser-induced, fluorescence-guided, angioplasty system, fluorescence spectra were recorded during exposure of normal and atherosclerotic cadaveric aortic tissue to argon ion laser irradiation. A characteristic increase in the fluorescence signal in the 520-560 nm spectral region for atheromatous tissue was observed after treatment of the samples with a tetracarboxylate ion dye (BTC). This allowed the development of a simple algorithm (based on the intensity difference) and a subsequent index of discrimination between normal and atheromatous tissue. Our results suggest that monitoring of this index through the catheter could enhance selective ablation.

The development of a new family of intracellular calcium probes

Four new potential fluorescent probes for Ca2+ using the coumarin moiety as a fluorophore have been synthesized and their spectral properties and binding affinities for Ca2+ determined. The most promising derivative for intracellular use, BTC, exhibits an excitation wavelength shift from 462 nm to 401 nm on binding Ca2+, with an emission wavelength of 530 nm. The quantum yield of this probe increases from 0.07 as the free indicator to 0.12 on binding Ca2+. BTC, loaded as its tetraacetoxymethyl ester (AM ester) into mouse myeloma P3X cells, responded only when cytoplasmic Ca2+ exceeded typical intracellular calcium concentrations. The dye, therefore, appears to be useful in excitatory cells or extracellular spaces with intracellular calcium concentrations high enough to saturate typical excitation ratio Ca2+ indicators such as Fura-2.

Synthetic transformations of cyclopropyl annulated dihydroisoquinolines

Isomeric 3-cyano-3-methyl-2-acetyl-cycloprop[c]isoquinolines, 5 and 6, were prepared by alkylation and cyclopropanation of Reissert compounds and their reactions under basic conditions were examined. Both compounds, under the influence of methoxide, yielded isoquinoline derived products resulting from cleavage of the peripheral C—C bond. The results are postulated to derive from attack of the methoxide on the acyl carbonyl, forming a tetrahedral adduct that undergoes ring opening. Key words: cyclopropanation, ring opening, tetrahedral complex, pyramidalization.

Striatally-mediated response of some structurally rigid analogues of dopamine

The potency of structurally rigid analogues of dopamine (DA) at striatal dopamine receptors was evaluated in rats using three types of assessments: (a) effectiveness in producing rotational and sniffing behaviors by intrastriatal injections (b) inhibition of [3H]-spiroperidol binding and (c) stimulation of adenylate cyclase activity. The compounds included apomorphine (APO) and its analogues, (R)-2,10,11-trihydroxyaporphine (R-THA) and (R)-2-hydroxy-10,11-methylenedioxyaporphine (MDO-APO), 2-amino-6,7-dihydroxyaminotetraline (ADTN) and its analogue, exo-2-amino-6,7-dihydroxybenzonorbornene (exo-amine). (R)-THA produced no stereotypy yet it was a potent inhibitor of [3H]-spiroperidol binding and adenylate cyclase activity. MDO-APO was quite active in inducing stereotypy and stimulating cyclase activity, but it showed low potency in displacing [3H]-spiroperidol. The exo-amine and ADTN were equally potent in enhancing rotation and sniffing intensity, however, the former was completely inactive in biochemical assessments. Except for (R)-THA, all DA analogues studied elicited dopaminomimetic behavioral activities of circling and sniffing. Relationships between the actions of these drugs in the behavioral and biochemical assessments are discussed.

Synthesis and dopamine receptor binding of exo- and endo-2-amino-6,7-dihydroxybenzonorbornene, rigid analogues of 2-amino-6,7-dihydroxytetrahydronaphthalene

Two bridged tricyclic analogues of 2-amino-6,7-dihydroxytetrahydronaphthalene (ADTN) in which the amino group is held rigidly in an equatorial and axial conformation, respectively, and in which the catechol ring is twisted out of the plane of the ethylamine chain have been synthesized and assayed for their effects on the binding of [3H]dopamine, [3H]apomorphine, and [3H]spiperone to calf and rat striatal homogenates. Up to concentrations of 2000 nM, these exo- and endo-2-amino-6,7-dihydroxybenzonorbornenes displayed no ability to displace any of the radioligands from their receptor sites in the calf and rat brain homogenates, in contrast to measured IC50 values of 6 and 3.1 nM for racemic ADTN vs. [3H]dopamine in the two preparations, respectively. The enantiomers of the exo amine showed no specific activity vs. [3H]dopamine in the two preparations, respectively. The enantiomers of the exo amine showed no specific activity vs [3H]dopamine. Although negative, these data are informative in molecular modeling of dopaminergic receptor interactions.