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Biomedical subjects

Y S Prabhakar

Publications and source records attributed to Y S Prabhakar.

At least 19 recordsLinked to original sources
PubMed2005

Topological descriptors in modeling the HIV inhibitory activity of 2-aryl-3-pyridyl-thiazolidin-4-ones.

The HIV-1 RT inhibitory activity of 2-(2,6-dihalophenyl)-3-(substituted pyridin-2-yl)-thiazolidin-4-ones has been analyzed with different topological descriptors obtained from DRAGON software. Here, simple topological descriptors (TOPO), Galvez topological charge indices (GVZ) and 2D autocorrelation descriptors (2DAUTO) have been found to yield good predictive models for the activity of these compounds. The correlations obtained from the TOPO class descriptors suggest that less extended or compact saturated structural templates would be better for the activity. The participating GVZ class descriptors suggest that they have same degree of influence on the activity. In 2DAUTO class, the large participation of descriptors of lags seven and three indicate the association of activity information with the seven and three centered structural fragments of these compounds. The physicochemical weighting components of these descriptors suggest homogeneous influence of mass, volume, electronegativity and/ or polarizability on the activity.

Anti-HIV Agents↗
PubMed1996

A theoretical study of hydrophobic fragment and factor constants of Hansch and Leo: estimation of a few non-available fragments and factors.

Hydrophobic fragment constants (f) of benzotriazol-2-yl and Ar-N[CO-]2 systems, and aliphatic H/S polar interaction factors F(H/S) in Cl2CHCONH-Ar and Cl3CCONH-Ar, of Hansch and Leo's constructionist approach, were estimated as 0.69 (standard deviation = 0.17), -1.98, 0.95 and 0.98 respectively. The validity of the first constant has been tested by calculating the log P of compounds not included in the regression.

Cyclopentanes↗
PubMed1992

QSAR study of HMGR inhibitors: 7-(heteroaryl)-3,5-dihydroxy-6-heptenoic (-heptanoic) acids.

The 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) inhibitory activity of pyridine- and pyrimidine-substituted 3,5-dihydroxyhept-6(E)-enoic acids and 7-(1H-pyrrol-3-yl)-substituted-3,5-dihydroxyhept-6(E)-enoic (-heptanoic) acids was quantitatively analysed using hydrophobicity, molar refractivity, electronic and Verloop's steric parameters. The results obtained were comparable to the earlier findings of 7-(aryl/biphenyl)-3,5-dihydroxy-6-heptenoic (-heptanoic) acids. The R'4-substituent of the aryl substituent of heteroaryl moiety was found to influence the inhibitory activity through its steric and electronic properties, and the equations confirm that substituents with minimum steric bulk, positive polar and negative resonance constants lead to better inhibitory activity. The changes in the heteroaryl moiety of the inhibitors did not correlate with the activity. Probably, the heteroaryl moiety of the inhibitors may be serving as a skeletal framework to hold the surrounding hydrophobic substituents.

Animals↗
PubMed1991

Quantum QSAR of the antirhinoviral activity of 9-benzylpurines.

The antirhinoviral activity of previously described 9-benzylpurines was quantitatively analysed using Huckel molecular orbital generated electronic parameters and physicochemical properties of substituents. Correlations with the activity against each of several serotypes of the virus were obtained but very few common requirements emerged. Our results emphasise the difficulties in identifying a compound with optimum structural features for broad spectrum antirhinovirus activity.

Algorithms↗
PubMed1989

Hepatoprotective effects of Wedelia calendulacea.

The alcoholic extract of whole plant Wedelia calendulacea exhibited protective activity against carbon tetrachloride-induced liver injury in vivo. The extract also increased the bile flow in rats suggesting a stimulation of liver secretory capacity. The minimum lethal dose was greater than 200 mg/kg p.o. in mice.

Animals↗
PubMed1989

QSAR study of phosphodiesterase inhibitory activity of imidazo[2,1-b]-quinazolines: active site analysis.

Published c-AMP phosphodiesterase inhibitory activities of 7-substituted-1,2,3,5-tetrahydro-2-oxoimidazo[2,1-b]quinazolines are used in a QSAR study to analyse a proposed model of the c-AMP PDE (type IV) active site. Based on the regression equations involving hydrophobic parameters and activities, additional subsites G1 and G2 are identified in the secondary binding region G, and steric hydrophobic tolerance at these subsites is discussed.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1989

QSAR study of the role of hydrophobicity in the activity of HMGR inhibitors.

The 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) inhibitory activity of 7-(aryl/biphenyl)-6-heptenoic acids was quantitatively analysed using hydrophobicity, van der Waals volume and electronic parameters. The activity was primarily a function of hydrophobicity, and was well correlated with the hydrophobicity of ortho and meta substituents on the aryl/biphenyl moiety. The electronic properties of para substituents on the aryl/biphenyl ring influenced the inhibition. Our equations predict that substituents with positive polar and sigma and negative resonance constants might lead to better inhibition.

Chemical Phenomena↗
PubMed1987

On the ethnomedical significance of the Arjun tree, Terminalia arjuna (Roxb.) Wight & Arnot.

Terminalia arjuna is an important cardiotonic plant described in the Ayurveda, the ancient Indian medical science. It is also believed to have the ability to cure hepatic, urogenital, venereal and viral diseases. An attempt is made here to analyse the available drug recipes using this plant from Sanskrit literature in the light of modern scientific knowledge. The chemistry and pharmacology of T. arjuna are also discussed, and areas of future investigations are identified.

Chemical Phenomena↗
PubMed1987

Quantitative structure-activity relationship study on amsacrine derivatives.

Various biological activities of amsacrine derivatives were analyzed in relation to various physico-chemical parameters. The in vitro activity parameters like DNA-binding and cell inhibition constants were found to have significant correlations but with varying physico-chemical parameters. DNA-binding constants were found to be the function of van der Waals volume and the cell inhibition constant to be the function of the hydrophobic parameter. But the in vivo antitumor activity parameters like optimal dose administered intraperitoneally in mice injected with P388 leukemia cells and the percentage increase in life span of treated animals over that of control animals were not found to be related with any property of the molecules.

Amsacrine↗
PubMed1986

Effect of molecular size on the activity of adriamycin analogues: a quantitative structure-activity relationship study.

The in vitro anti-tumor activity (inhibition of human lymphoblastic leukemia cells) of some adriamycin analogues is found to be significantly correlated with the van Waals volume (VW) of the substituents. Activity is also found to be well correlated with first-order valence molecular connectivity index (1 chi V) but no correlation is found to exist between it and the hydrophobic parameter, log P (P: octanol-water partition coefficient). On the basis of these findings, it is suggested that the activity would be affected by the steric influence and to some extent by the electronic character of the substituents. From the correlating equations, it is observed that the size of C-7 glycoside ring and that of NHR2 group at its third position would greatly affect the activity. The size of C-14-R1 however, is not found to have much effect on the activity.

Antineoplastic Agents↗
PubMed1985

Quantitative correlations of biological activities of dactinomycin analogs and methotrexate derivatives with van der Waals volume.

The biological activities namely the ability to bind with DNA base pairs and the in vitro inhibition of human lymphoblastic leukemia cells of certain C-7- and N2-substituted dactinomycin (actinomycin D, AMD) analogs, and the growth inhibitory activity of a series of side chain substituted methotrexate (MTX) derivatives against L 1210 mouse leukemia cells in culture and their binding affinity for dihydrofolate reductase (DHFR) enzyme extracted from this system and L. casei are found to be significantly correlated with van der Waals volume of the substituents. In case of MTX derivatives, not only the side chain substituted analogs but certain ring substituted analogs, too, are shown to have their different activities dependent upon the Vw of the substituents. In case of side chain substituted analogs, however, it is found that the size of the substituent of alpha-position produces a greater effect on the activity than that of gamma-position. Based on the correlating equations obtained it is assumed that in these cases the drug-receptor interaction might be involving either hydrophobic interaction or the van der Waals type of interaction.

Animals↗
PubMed1984

Correlation of biological activities of mesoionic and benz-fused mesoionic xanthine analogs with van der Waals volume and molecular connectivity.

The adenosine cyclic 3',5'-monophosphate (c-AMP) phosphodiesterase (PDE) inhibitory activity of a series of mesoionic 1,3,4-thiadiazolopyrimidines and of a group of benz-fused mesoionic xanthine analogs are found to be significantly correlated with the van der Waals volume (VW) of the substituents or the first order valence connectivity index (1 chi V) of the molecule. From the correlating equations it is observed that the size of the substituents at certain positions, of pyrimidine ring particularly, in the molecule are determinative to the activity. Further based on these equations it may be suggested that PDE inhibition by this class of drugs involves either hydrophobic interaction or van der Waals type of interaction. In certain cases steric and electronic factors are also indicated to affect the inhibition.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1984

A quantitative analysis of steric and hydrophobic effects in ribonucleoside diphosphate reductase inhibition by thiosemicarbazones.

Ribonucleoside diphosphate reductase (RDR) inhibitory activity of 2-formylpyridine and 1-formylisoquinoline thiosemicarbazones is quantitatively analysed in relation to a steric parameter (van der Waals volume, VW) and the hydrophobic parameter logP. The activity is found to be significantly correlated with VW and very poorly with logP. On the basis of this, it is inferred that RDR inhibition by thiosemicarbazones is very sensitive to steric effects and is little influenced by the hydrophobic character of the molecules.

Chemical Phenomena↗
PubMed1983

OSAR studies on 4-hydroxyquinoline-3-carboxylic acids as inhibitors of cell respiration using molecular connectivity and van der Waals volume.

The enzyme inhibition activities of 4-hydroxyquinoline-3-carboxylic acids against three isolated enzyme systems namely mitochondrial malate dehydrogenase, cytoplasmic malate dehydrogenase, and skeletal muscle lactate dehydrogenase, all involved in respiratory pathway, are found to be significantly correlated with first-order valence molecular connectivity (1 chi v) and van der Waals volume (Vw). The correlations obtained provide much simple rationale to design more active congeners and facilitate the prediction of activity of new compounds.

Animals↗