A quantitative structure-activity relationship study on some HIV-1 protease inhibitors using molecular connectivity index

A quantitative structure-activity relationship (QSAR) study has been made on two different series of tetrahydropyrimidinones acting as HIV-1 protease inhibitors. A structural parameter, the first order valence molecular connectivity index ((1)chi(v)), has been used to account for the variation in the activity. The protease inhibition activity as well as the antiviral potency of the compounds are found to be significantly correlated with (1)chi(v) of P(2)/P(2') substituents attached to the two nitrogens N1 and N3, suggesting that substituents containing less electronegative and more saturated atoms, meaning thereby the less polar or more hydrophobic substituents, will be more advantageous. Further, if P(2) and P(2') are dissimilar, the former is found to be more effective than the latter. This difference is attributed to a conformational change in the enzyme that may be more favorable to P(2) binding than to P(2') binding.

Quantitative structure-activity relationships of antianginal drugs

Quantitative structure-activity relationships (QSARs) of various classes of antianginal drugs, e.g. nitrates, beta-adrenergic blocking agents (beta-blockers), and calcium channel blockers (calcium antagonists), have been reviewed. This review gives an overall picture of the mode of action of each class of drugs and points out the specific physicochemical and structural properties that govern their activity. It is observed that in almost all kinds of antianginal drugs the lipophilic factor plays an important role and the next important factor seems to be the steric ones. The electronic factors are found to be occasionally important. In the case of beta-blockers, the most common factor that appeared to govern the activity remained the lipophilicity. In nitrates, too, the activity is observed to primarily depend upon the lipophilicity. In calcium channel blockers, however, the dominant effect is seen to be of steric factors. The steric roles may be essential in drug-receptor interactions, which seem to involve both hydrophobic, and to a lesser extent, electronic interactions.

Quantitative structure-activity relationships of cardiotonic agents

Quantitative structure-activity relationships (QSARs) of different cardiotonic agents are presented. A critical analysis of all QSARs provides a very vivid picture of the mechanisms of varying cardiotonic agents. The cardiotonics can be broadly put into 2 categories: cardiac glycosides and nonglycoside cardiotonics, which include phosphodiesterase of type III (PDE III) inhibitors, sympathomimetic (adrenergic) stimulants, A1-selective adenosine antagonists, Ca2+ channel activators and vasopressin antagonists. For cardiac glycosides, QSARs reveal that the position of carbonyl oxygen in their lactone moiety and shifting of the lactone ring from its original position or its replacement by another group would be crucial for their activity. The carbonyl group or its isostere like CN is indicated to be the sole binding entity and the hydrogen bonding through this group is considered to be the most likely binding force. For nonglycoside cardiotonics that include PDE III inhibitors and A1-selective antagonists, a five-point model has been established for their activity, the salient features of which are: (1) the presence of a strong dipole, (2) an adjacent acidic proton, (3) a methyl-sized lipophilic space, (4) a relatively flat overall topography and (5) a basic or hydrogen-bond acceptor site opposite to the dipole. For Ca2+ channel activators, the importance of steric, electrostatic, lipophilic and hydrogen-bonding properties of molecules is indicated, while for vasopressin antagonists the lipophilic and electronic properties are suggested to be the most important.

Quantitative structure-activity relationship studies on cyclic cyanoguanidines acting as HIV-1 protease inhibitors

A quantitative structure-activity relationship study has been performed on some cyclic cyanoguanidines that inhibit the enzyme HIV-1 protease (HIV-1-PR) and exhibit antiviral potency, and the results have been compared with those of cyclic urea derivatives. Both the enzyme inhibition activity and antiviral potency in cyclic cyanoguanidines as well as in cyclic urea derivatives are found to be primarily governed by hydrophobic property of substituents attached to nitrogen (P2/P2') and further enhanced by OH or NH2 group, if any, present in the substituents. However, aromatic substituents are found to be unfavourable to both the activities of cyclic cyanoguanidines but not to any activity of cyclic urea derivatives. Cyclic urea derivatives are indicated to be more potent than cyclic cyanoguanidines. A model for the interaction of cyclic cyanoguanidines with the receptor is proposed.

Quantitative structure-activity relationships of some HIV-protease inhibitors

A quantitative structure-activity relationship (QSAR) study has been made on different series of cycloalkylpyranones acting as human-immunodeficiency-virus type 1 (HIV-1) protease inhibitors. The results suggest that the enzyme binding affinity of the compounds would be favoured by a cyclooctyl ring, a 3-cyclopropylphenylmethyl substituent at the pyranone ring, and a 4-CN-2-pyridine-, an N-Me-imidazole-, or a 3- or 4-CN-phenyl-sulfonamide group at the meta position of the phenyl ring of the 3-substituent.

Quantitative structure-activity relationship study on some nonpeptidal cholecystokinin antagonists

A quantitative structure-activity relationship (QSAR) analysis has been performed on a series of 1,4-benzodiazepine derivatives, which were found to act as antagonists of cholecystokinin (CCK), a gastrointestinal peptide hormone. The CCK acts with three different receptor subtypes termed as CCK-A, CCK-B, and gastrin receptor, which can be found in peripheral system, brain, and stomach, respectively. With all the three subtypes, the binding of the compounds is found to significantly depend on the lipophilicity of the compounds and their ability to form the hydrogen bonds with the receptor. However, the binding sites in CCK-A receptor seem to be slightly rigid as compared to those in CCK-B or gastrin receptor. The latter two appear to have similar binding features.

Non union of stress fracture of the tibia and fibula with osteoarthritis of the knee joint

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Quantitative structure-activity relationships of antihypertensive agents

Quantitative structure-activity relationships of various classes of antihypertensive agents, e.g., sympatholytic agents, diuretics, direct or peripheral vasodilators, potassium channel activators, angiotensin-converting enzyme inhibitors, renin inhibitors and miscellaneous agents (platelet aggregation inhibitors) are reviewed. This review gives an overall picture of the mode of action of each class of drugs and points out their specific physicochemical and structural properties governing their action. For example, in the case of centrally acting drugs (sympatholytic agents) it has surfaced that the prime factors governing their activity are lipophilic and steric properties of the molecules, and at the receptor level a charge-transfer complex is formed between the molecule and the receptor. It is, however, observed that for peripherally acting sympatholytic agents the prime role is played by only lipophilicity. In the case of diuretics, the electronic characters of molecules are found to be more dominant than their lipophilic property, but for direct vasodilators and ACE inhibitors both electronic and lipophilic properties seem to be equally important. In renin or platelet aggregation inhibitors, the structural properties appear to be more important. However, the fundamental property that is overwhelmingly involved in the majority of antihypertensive agents appears to be the lipophilicity, suggesting that in most of the cases the hydrophobic interaction would play the major role in drug action.

Quantitative structure-activity relationships of antiarrhythmic drugs

A Comprehensive review of quantitative structure-activity relationship (QSAR) studies on antiarrhythmic agents is presented. From the discussion point of view, the antiarrhythmic agents have been put into two broad classes: specific and nonspecific. While the main members of the former class can be beta-adrenergic blocking agents (beta-blockers), any chemical that can act directly on the myocardial cell membrane, producing a cardiodepressant effect via changes in basic electrophysiological properties of the membrane, such as automaticity, excitability, conductivity, and refractoriness, has been put in the latter class. QSARs exhibit that the biological actions of a variety of drugs belonging to any class depend primarily on the lipophilic haracter of the molecule or substituents. Thus, the hydrophobic interaction is found to play a dominant role in the action of antiarrhythmic agents. In certain cases, the QSARs also exhibit the role of electronic parameters, suggesting that certain receptors may have electronic site also, permitting the drugs to involve in some electronic interactions, too.

Quantitative Structure-Activity Relationships of Antiarrhythmic Drugs

Abstract:

A Comprehensive review of quantitative structure-activity relationship (QSAR) studies on antiarrhythmic agents is presented. From the discussion point of view, the antiarrhythmic agents have been put into two broad classes: specific and nonspecific. While the main members of the former class can be -adrenergic blocking agents ( -blockers), any chemical that can act directly on the myocardial cell membrane, producing a cardiodepressant effect via changes in basic electrophysiological properties of the membrane, such as automaticity, excitability, conductivity, and refractoriness. has been put in the latter class. QSARs exhibit that the biological actions of a variety of drugs belonging to any class depend primarily on the Jipophilic haracter of the molecule or substituents. Thus, the hydrophobic interaction is found to play a dominant role in the action of antiarrhythmic agents. In certain cases, the QSARs also exhibit the role of electronic parameters, suggesting that certain receptors may have electronic site also, permitting the drugs to involve in some electronic interactions, too.

A quantitative structure-activity relationship study on some sulfolanes and arylthiomethanes acting as HIV-1 protease inhibitors

A quantitative structure-activity relationship (QSAR) study on some sulfolanes and arylthiomethanes acting as human immunodeficiency virus-1 (HIV-1) protease inhibitors reveals that in the case of sulfolanes an octahydropyrindene ring and a five-membered 3(S)-sulfolane ring with a hydrophobic 2-substituent (cis to 3-substituent) will be crucial for the inhibition activity. The binding of a sulfolane, which is a nonpeptidic molecule, with the enzyme is shown to partly mimic the binding of a peptidic inhibitor. The 2-substituent is found to have strong hydrophobic interaction with the receptor. Similarly, in the case of arylthiomethanes, one of the substituents of the methane is found to have strong hydrophobic interaction with the enzyme, while the aryl substituent (4-hydroxy-6-phenyl-2-oxo-2H-pyran-3-yl) is assumed to be involved in the hydrogen bondings.

Quantitative structure-activity relationship studies on some nonbenzodiazepine series of compounds acting at the benzodiazepine receptor

Quantitative structure-activity relationship (QSAR) studies have been made on a few non-benzodiazepine series of compounds such as 3-substituted imidazo[1,2-b]pyridazines, 2-phenylimidazo[1,2-alpha]pyridines, 2-(alkoxycarbonyl) imidazo[2,1-b]benzothiazoles, and 2-arylquinolines. For the first series of compounds a Fujita-Ban approach has been followed, which revealed the highest activity contribution for 3,4-OCH2O group of 2-phenyl moiety and for a methoxy group at 6-position. For the rest of the series, a Hansch approach has been adopted. The hydrophobic and electronic properties of the various substituents have been found to play major roles in the binding of these compounds with the receptor. Based on these studies, a hypothetical model for the drug-receptor interaction has been proposed.

Quantitative structure-activity relationship studies on cyclic urea-based HIV protease inhibitors

A quantitative structure-activity relationship (QSAR) study is described on some cyclic ureas that inhibit the enzyme HIV-1 protease (HIV-1-PR) and exhibit antiviral potency. Both the enzyme inhibition activity and the antiviral potency were found to be primarily governed by the hydrophobic property of the substituents at the nitrogens (N2/N2') of the urea. Adjacent to the nitrogens, the C1/C1'-substituents are, however, found to affect the activity (inhibition) by their molecular size. The essential binding of the ureas with the receptor is, however, through multiple hydrogen bonding, where the substituents, too, can participate in such binding if they are capable of doing so. A schematic diagram of the overall interaction of the inhibitors with the receptor is presented.

Quantitative structure-activity relationship studies on some anti-human-immunodeficiency-virus-1 (anti-HIV-1) drugs: viral reverse transcriptase inhibitors

The anti-HIV-1 activity of some 3-[(benzoxazol-2-ylmethyl)amino]-, 3-[(benzoxazol-2-yl)ethyl]-, 3-[N-(phthalimidomethyl)amino]- and 3-[N-(phthalimido)ethyl]-5-ethyl-6-methyl pyridin-2(1H)-one derivatives, that have been found to elicit their action through the allosteric inhibition of the enzyme viral reverse transcriptase (VRT), have been analysed in relation to the physicochemical properties of the molecules. Significant correlations were obtained between the activity and the hydrophobic and electronic constants of substituents and van der Waals' volume of the linker chain. Based on these findings the mechanism of action of these drugs is discussed.

Quantitative structure-activity relationship studies on some viral reverse transcriptase inhibitors acting as anti-HIV-1 agents

The anti-HIV-1 and cytotoxic activities of some viral reverse transcriptase inhibitors, namely the analogues of [1-[2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-xylo- and -ribofuranosyl]]-3'-spiro-5" -[4"-amino-1",2"-oxathiole 2",2"-dioxide] (TSAO) pyrimidine and pyrimidine modified-nucleotides, are analysed in relation to their physicochemical and molecular properties. The antiviral activities of the compounds are found to be significantly correlated with hydrophobic and electronic properties of the molecules, but no physicochemical parameters were found to be correlated with the cytotoxic effects of the compounds. This difference is exploited to improve the selectivity of the compounds. It is observed that TSAO can provide potent anti-HIV-1 drugs with a disubstituted thymine ring, in which a substituent may be at the N3-position. The disubstitution reduces the cytotoxicity, and substituents' hydrophobicity and electron donating character enhance the antiviral activity.

Quantitative structure-activity relationship studies on anti-HIV-1 TIBO derivatives as inhibitors of viral reverse transcriptase

The anti-human-immunodeficiency-virus (HIV-1) activity of the derivatives of 4,5,6,7-tetrahydro-5-methylimidazo [4,5,1-jk] [1,4] benzodiazepin-2(1H)-one (TIBO) that have been found to elicit their action through the allosteric inhibition of the enzyme viral reverse transcriptase (VRT) is analysed in relation to the physicochemical properties of the molecules. Significant correlations are obtained between the activity and the hydrophobic constant and some dummy parameters of substituents. Based on these findings, the mechanism of action of these anti-HIV drugs is discussed.

Lateral condylar fractures of the humerus in children: fixation with partially threaded 4.0-mm AO cancellous screws

Thirty-seven children with fresh, displaced (more than 2 mm in any direction) fractures of the lateral condyle of the humerus were treated by open reduction and internal fixation with a partially threaded 4.0-mm diameter AO lag screw. They were reviewed at a mean follow-up of 4.8 years. Painless, full-elbow movements were obtained in 36 cases. Delayed union, with loss of 10 degrees of elbow motion, was observed in one case (2.72%). Radiologically, less than 4 degrees of varus deviation, compared with the contralateral side, was found in four cases (10.8%). Mild fishtailing was observed in three cases (8.18%). Nonunion, avascular necrosis or clinically significant premature epiphysial fusion was not observed. Elbow function was excellent, irrespective of minor radiologic abnormalities.