CLINDAMYCIN: EFFECTS ON PLASMA LIPID PROFILE AND PEROXIDATION PARAMETERS IN RABBIT BLOOD PLASMA.

Alteration of plasma lipid profile and induction of lipid peroxidation may take place due to drug effect, which may be correlated with adverse drug reactions and drug-induced toxicity. Considering this fact, the present in vivo study was carried out to evaluate the effect of clindamycin on plasma lipid profile and peroxidation parameters alone and in combination with ascorbic acid, a promising antioxidant. After administering drug and antioxidant alone and in combination in rabbit, it was found that clindamycin had mild lipid peroxidation induction and profile alteration capacity, which can be arrested on co-administration of ascorbic acid.

Protective effect of ascorbic acid on netilmicin-induced lipid profile and peroxidation parameters in rabbit blood plasma.

A drug may cause alteration in blood-lipid profile and induce lipid peroxidation phenomena on administration in the body. Antioxidant may play beneficial role to control the negative alteration in lipid profile and lipid peroxidation. In view of this context, the present in vivo study was carried out to evaluate the role of ascorbic acid as antioxidant on netilmicin-induced alteration of blood lipid profile and peroxidation parameters. Rabbits were used as experimental animals and blood was collected to estimate blood-lipid profiles, such as total cholesterol (TCh), high density lipoprotein cholesterol (HDL-Ch), low density lipoprotein cholesterol (LDL-Ch), very low density lipoprotein cholesterol (VLDL-Ch), triglycerides (Tg), phospholipids (PL), and total lipids (TL), as well as peroxidation parameters, such as malondialdehyde (MDA), 4-hydroxy-2-nonenal (HNE), reduced glutathione (GSH) and nitric oxide (NO). The results revealed that netilmicin caused significant enhancement of MDA, HNE, TCh, LDL-Ch, VLDL-Ch, Tg levels and reduction in GSH, NO, HDL-Ch, PL, TL levels. On co-administration, ascorbic acid was found to be effective in reducing netilmicin-induced negative alterations of the above parameters.

Gentamicin induced lipid peroxidation and its control with ascorbic acid.

Lipid peroxidation is the oxidative deterioration of polyunsaturated fatty acids (PUFAs), which is a free radical related process. Studies showed that reactive oxygen species (ROS) are involved in a diversity of biological phenomena including atherosclerosis, neurodegenerative diseases, carcinogenesis etc. ROS and other pro-oxidant agents have the capacity to exhibit oxidative decomposition of PUFAs of membrane phospholipids leading to the formation of toxic end products, including malonyldialdehyde (MDA), 4-hydroxy-2-nonenal (HNE) etc. Drug-induced lipid peroxidation contributes to significant toxicity. Antioxidants have the ability to reduce generation of free radicals in the body by inhibiting lipid peroxidation process. In view of this concept, the present in vivo study is carried out to evaluate the inhibitory effect of ascorbic acid on lipid peroxidation induced by gentamicin, an aminoglycoside antibiotic. Levels of MDA, HNE, reduced glutathione (GSH) and nitric oxide (NO) are used as markers of lipid peroxidation. Rabbits divided into different experimental groups are treated with drug and co-administered with ascorbic acid. The levels of MDA, HNE, GSH and NO in the blood are estimated and compared with the control. The results revealed that gentamicin significantly increases MDA and HNE contents, but decreases GSH and NO levels; and ascorbic acid on co-administration has capability to inhibit drug-induced lipid peroxidation.

Inhibition of lipid peroxidation induced by hydroxyprogesterone caproate by some conventional antioxidants in goat liver homogenates.

Among the cellular molecules, lipids containing unsaturated fatty acids with more than one double bond are particularly susceptible to action of free radicals. The resulting reaction, known as lipid peroxidation, has deleterious effect on biological membranes, leading sometimes even to disrupting them, or influencing their structure and function. Different toxic products are formed during this process. In this context, the present study was made to explore the suppressive actions of some conventional antioxidant compounds e.g., ascorbic acid, alpha-tocopherol and probucol on lipid peroxidation induced by hydroxyprogesterone caproate (HP), a progestogenic compound. The study has been performed using goat liver homogenate. It was found that HP increased thiobarbituric acid reactive substance i.e., malondialdehyde (MDA) and also other major toxic end product of lipid peroxidantion - 4-hydroxynonenal (4-HNE). HP decreased significantly the levels of reduced glutathione (GSH) and nitric oxide (NO) in the liver homogenates. This suggests that HP caused lipid peroxidation to a significant extent, which may be related to the toxic potential of the drug. It was further found that all of the above mentioned antioxidants could suppress HP-induced lipid peroxidation to the significant extent.

Exploring effects of different nonsteroidal antiinflammatory drugs on lipid peroxidation. Part II. 4-HNE profile.

Non-steroidal anti-inflammatory drugs (NSAIDs) are common in alleviating pain, pyrexia and inflammation, in patients with rheumatoid arthritis and osteoarthritis. As these drugs are associated with high incidence of gastrointestinal ulceration, bleeding and kidney damage which may be linked with lipid peroxidation. our study was aimed to examine lipid peroxidation induction capacity of NSAIDs (diclofenac sodium, ibuprofen, flurbiprofen, paracetamol, nimesulide, celecoxib and indomethacin) by determining 4-hydroxy-2-nonenal (4-HNE) concentration as an index of lipid peroxidation and to see the suppressive potential of ascorbic acid on NSAID induced lipid peroxidation. The results suggest that diclofenac sodium, ibuprofen, flurbiprofen, paracetamol, nimesulide and celecoxib exerted mild antioxidant activity. Indomethacin exerted statistically significant increase in 4-HNE content, indicating statistically significant peroxidation activity. Ascorbic acid could significantly reduce indomethacin-induced lipid peroxidation.

Comparative QSAR modeling of COX-2 inhibitor 1,2-diarylimidazoles using E-state and physicochemical parameters.

Considering importance of developing selective COX-2 inhibitors, COX-2 binding affinity data of 4-(2-aryl-1-imidazolyl)-phenyl methyl sulfones and sulfonamides (n = 83) have been modeled using electrotopological state (E-state) index as electronic parameter, hydrophobic substituent constant (pi) and molar refractivity (MR) of aryl ring substituents as lipophilic and steric parameters, respectively. Additionally, suitable dummy parameters have been used for the development of multiple regression equations in a stepwise manner. The study suggests that lipophilicity of ortho, meta and para substituents of the aryl ring increases the binding affinity, while molar refractivity (MR) of ortho and meta substituents of the aryl ring decreases the binding affinity. Again, electron-withdrawing substituents at meta and para positions of the aryl ring increase the binding affinity. Additionally, a 4-fluoro substituent on the aryl ring, a trifluoromethyl substituent at R position and simultaneous presence of 3-chloro and 4-methyl groups on the aryl ring are conducive to the binding affinity. Also, an amino substituent is preferred over a methyl group at R2 position suggesting preference of the sulfonamide moiety over the methyl sulfone moiety for the COX-2 binding affinity. Furthermore, importance of E-state values of different atoms in the generated relations suggests the influence of electron density distribution over the 1,2-diarylimidazole nucleus for the binding affinity. For this data set, E-state parameters perform better as electronic parameters in comparison to Hammett sigma parameters. When lipophilic whole molecular descriptor (ClogP) is used, instead of hydrophobic substituent constant (pi), the former performs better than the latter.

In vitro evaluation of protective effects of ascorbic acid and water extract of Spirulina plantesis (blue green algae) on 5-fluorouracil-induced lipid peroxidation.

Considering drug-induced lipid peroxidation as a possible mediator of drug-induced toxicity and exploiting the free radical scavenging action of antioxidants, the present study was designed to evaluate the protective effects of ascorbic acid (AA) and water extract of Spirulina plantesis (SP) to minimize 5-fluorouracil (5-FU)-induced lipid peroxidation. The study has been performed in vitro using goat liver as an experimental model. This evaluation was done by measuring the malondialdehyde (MDA), reduced glutathione (GSH), 4-hydroxy-2-nonenal (4-HNE) and nitric oxide (NO) content of the tissue as markers of lipid peroxidation. The results suggest that ascorbic acid and water extract of Spirulina plantesis could suppress the 5-FU-induced lipid peroxidation to a significant extent.

Exploring effects of different nonsteroidal antiinflammatory drugs on malondialdehyde profile.

As a part of our ongoing effort to explore drug induced lipid peroxidation in relation to drug-induced toxicity, this study was undertaken to determine whether nonsteroidal anti-inflammatory drugs (NSAIDs), namely, diclofenac sodium, ibuprofen, flurbiprofen, paracetamol, nimesulide, celecoxib and indomethacin are involved in oxidative/antioxidative processes by determining malondialdehyde (MDA) concentration as an index of lipid peroxidation. Considering lipid peroxidation, a possible mediator of toxicity, an attempt was made to see the suppressive action of ascorbic acid, a conventional antioxidant compound, on NSAID-induced lipid peroxidation. It was found that diclofenac sodium, ibuprofen, flurbiprofen and paracetamol exerted statistically significant decrease of MDA content, suggesting a potential of the molecules to suppress the lipid peroxidation. At earlier stage of incubation nimesulide shows statistically significant decrease of MDA content followed by lipid peroxidation induction at the later stage of incubation period, suggesting involvement of nimesulide in antioxidative/oxidative processes. Celecoxib and indomethacin both exerted statistically significant increase of MDA content, representing significant peroxidation activity. Ascorbic acid, a promising antioxidant, could significantly reduce celecoxib and indomethacin induced lipid peroxidation.

A study on ceftriaxone-induced lipid peroxidation using 4-hydroxy-2-nonenal as model marker.

4-Hydroxy-2-nonenal, an indicator of lipid peroxidation process. was used as model marker to explore ceftriaxone-induced lipid peroxidation in goat liver homogenate. Ceftriaxone was found to induce lipid peroxidation significantly. It was further found that ascorbic acid could significantly arrest ceftriaxone-induced lipid peroxidation. The results corroborate the earlier findings with malondialdehyde as model marker.

Evaluation of ascorbic acid as suppressor of cyclophosphamide induced lipid peroxidation using common laboratory markers.

The present study deals with exploration of lipid peroxidation induction capacity of cyclophosphamide, an anticancer drug, and in vitro evaluation of ascorbic acid as a suppressor of cyclophosphamide induced lipid peroxidation. Goat liver homogenate has been used as the lipid source. This evaluation was done by measuring the malondialdehyde, 4-hydroxy-2-nonenal, reduced glutathione and nitric oxide content of the tissue as markers of lipid peroxidation. The study revealed that ascorbic acid could suppress the drug induced lipid peroxidation to a significant extent.

Exploring selectivity requirements for COX-2 versus COX-1 binding of 2-(5-phenyl-pyrazol-1-yl)-5-methanesulfonylpyridines using topological and physico-chemical parameters.

Considering the current need for development of selective cyclooxygenase-2 (COX-2) inhibitors, an attempt has been made to explore physico-chemical requirements of 2-(5-phenyl-pyrazol-1-yl)-5-methanesulfonylpyridines for binding with COX-1 and COX-2 enzyme subtypes and also to explore the selectivity requirements. In this study, E-states of different common atoms of the molecules (calculated according to Kier & Hall), first order valence connectivity and physicochemical parameters (hydrophobicity pi, Hammett sigma and molar refractivity MR of different ring substituents) were used as independent variables along with suitable dummy parameters in the stepwise regression method. The best equation describing COX-1 binding affinity [n = 25, Q2 = 0.606, R(a)2 = 0.702, R2 = 0.752, R = 0.867, s = 0.447, F = 15.2 (df 4, 20)] suggests that the COX-1 binding affinity increases in the presence of a halogen substituent at R1 position and a p-alkoxy or p-methylthio substituent at R2 position. Furthermore, a difluoromethyl group is preferred over a trifluoromethyl group at R position for the COX-1 binding. The best equation describing COX-2 binding affinity [n = 32, Q2 = 0.622, R(a)2= 0.692, R2 = 0.732, R = 0.856, s = 0.265, F = 18.4 (df 4, 27)] shows that the COX-2 binding affinity increases with the presence of a halogen substituent at R1 position and increase of size of R2 substituents. However, it decreases in case of simultaneous presence of 3-chloro and 4-methoxy groups on the phenyl nucleus and in the presence of highly lipophilic R2 substituents. The best selectivity relation [n = 25, Q2 = 0.455, R(a)2 = 0.605, R2 = 0.670, R = 0.819, s = 0.423, F = 10.2 (df 4, 20)] suggests that the COX-2 selectivity decreases in the presence of p-alkoxy group and electron-withdrawing para substituents at R2 position. Again, a trifluoro group is conductive for the selectivity instead of a difluoromethyl group at R position. Furthermore, branching may also play significant role in determining the selectivity as evidenced from the connectivity parameter.

Exploring QSAR with E-state index: selectivity requirements for COX-2 versus COX-1 binding of terphenyl methyl sulfones and sulfonamides.

An attempt has been made to explore selectivity requirements for cyclooxygenase-2 (COX-2) versus cyclooxygenase-1 (COX-1) binding of terphenyl methyl sulfones and sulfonamides using electrotopological state (E-state) index and suitable indicator parameters. Multiple linear regression analyses produced statistically acceptable equations: the best relation based on 'all-possible-subsets regression' for COX-1 binding (n=18) showed predicted variance and explained variance of 0.675 and 0.777, respectively, while in case of the best equation for COX-2 binding (n=38), these values rose to 0.842 and 0.874, respectively. For the selectivity relation (n=17), predicted variance and explained variance values were 0.601 and 0.687, respectively. Based on the results of the analyses, three important sites have been suggested: sites A (methylsulfonyl or aminosulfonyl moiety), B (central phenyl ring), and C (terminal phenyl ring containing different substituents). All three sites are important for COX-2 binding while sites B and C are important for COX-1 binding. For COX-2 selectivity, only site C plays an important role. The study shows the utility of E-state index in developing statistically acceptable model having direct physicochemical significance.

Exploring QSAR of melatonin receptor ligand benzofuran derivatives using E-state index.

Considering the recent challenge to the medicinal chemists for the development of selective melatonin receptor ligands, an attempt has been made to explore physicochemical requirements of benzofuran derivatives for binding with human MT1 and MT2 receptor subtypes and also to explore selectivity requirements. In this study, E-states of different common atoms of the molecules (calculated according to Kier and Hall) and physicochemical parameters (partition coefficient and molar refractivity) were used as independent variables along with suitable dummy parameters. The best equation describing MT1 binding affinity [n = 34, Q2 = 0.670, Ra2 = 0.790, R2 = 0.822, R = 0.907, s = 0.609, F = 25.8 (df 5, 28)] suggests that the binding affinity decreases as the value of n (number of CH2 spacer beside R2) increases while it increases with rise in electrotopological state values of different atoms of the benzofuran ring. Again, presence of methoxy group at R1 and hydrogen, unsubstituted phenyl or fluoro-substituted phenyl group at R2 is conducive to the MT1 binding affinity. The binding affinity decreases if furyl substitution at R3 position is present. The best equation describing MT2 binding affinity [n = 34, Q2 = 0.602, Ra2 = 0.755, R2 = 0.792, R = 0.890, s = 0.584, F = 213 (df 5, 28)] shows that the MT2 binding affinity depends on the similar factors as described for MT1 binding affinity; however, the contributions of the factors for the two affinities are different to some extent as evidenced from the regression coefficients. Among the selectivity relations, the best equation [n = 33, Q2 = 0.496 Ra2 = 0.681, R2 = 0.721, R = 0.849, s = 0.458, F = 18.1(df 4, 28)] suggests that MT2 binding increases with increase in value of n, presence of methoxy group at R1, and E-state values of different atoms of the benzofuran ring, while it decreases in presence of furyl group at R3 position.

QSAR of adenosine receptor antagonists. Part 3: Exploring physicochemical requirements for selective binding of 1,2,4-triazolo[5,1-i]purine derivatives with human adenosine A3 receptor subtype.

Considering potential of selective adenosine A3 receptor antagonists in the development of prospective therapeutic agents, an attempt has been made to explore selectivity requirements of 1,2,4-triazolo[5,1-i]purine derivatives for binding with cloned human adenosine A3 receptor subtype. In this study, partition coefficient (logP) values of the molecules (calculated by Crippen's fragmentation method) and Wang-Ford charges of the common atoms of the triazolopurine nucleus (calculated from molecular electrostatic potential surface of energy minimized geometry using AM1 technique) were used as independent variables along with suitable dummy parameters. The best equation describing A3 binding affinity [n=29, Q2=0.796, Ra2=0.853, R2=0.874, R=0.935, s=0.342, F=41.5 (df 4,24), SDEP=0.396] showed parabolic relation with logP (optimum value being 4.134). Further, it was found that an aromatic substituent conjugated with the triazole nucleus should be present at R2 position for A3 binding affinity. Again, high negative charges on N2 and N4 are conducive to the binding affinity. While exploring selectivity requirements of the compounds for binding with A3 receptor over that with A2A receptor, the selectivity relation [n=23, Q2=0.909, Ra2=0.918, R2=0.933, R=0.966, s=0.401, F=62.4 (df 4,18), SDEP=0.412] showed that an aromatic R2 substituent conjugated with the triazole nucleus contributes significantly to the selectivity. Again, presence of a 4-substituted-phenyl ring (except 4-OH-phenyl and 4-CH3-phenyl) at R2 position also increases selectivity. Further, charge difference between N2 and N11 (negative charge on the former should be higher and that on the latter should be less) contributes significantly to the selectivity. In addition, negative charge on N7 is conducive while presence of substituents like propyl, butyl, pentyl or phenyl at R1 position is detrimental for the A3 selectivity.

QSAR modeling of globulin binding affinity of corticosteroids using AM1 calculations.

A quantitative structure-activity analysis of binding affinity of a series of 30 steroids for corticosteroid-binding globulin was performed using Wang-Ford charges of the non-hydrogen common atoms obtained from molecular electrostatic potential surface of AM1 optimized energy-minimized geometries of the compounds. Attempts were made to include lipophilicity (logP) and molar refractivity (MR) values of the whole molecules in the multivariate relations. The final relations were subjected to 'leave-one-out' cross-validation to check their predictive potential. It was found from the study that the charges of different atoms of the steroid nucleus [atoms 3, 4, 5 (ring A), 8, 9 (fusion points of rings B and C) and 16 (ring D)] contribute significantly to the binding affinity. This suggests the importance of these atoms/sites for the globulin binding affinity, which is also supported by previous reports on structure-activity relations of corticosteroids. Further, molar refractivity shows parabolic relation with the binding affinity, which indicates the possibility of dispersion interactions. The statistical qualities of the final equations generated in the present study (predicted variance 77-82%; explained variance 83-87%) are better than those of some of the previously reported models.

Unusual fluorescence of W168 in Plasmodium falciparum triosephosphate isomerase, probed by single-tryptophan mutants.

Plasmodium falciparum triosephosphate isomerase (PfTIM) contains two tryptophan residues, W11 and W168. One is positioned in the interior of the protein, and the other is located on the active-site loop 6. Two single-tryptophan mutants, W11F and W168F, were constructed to evaluate the contributions of each chromophore to the fluorescence of the wild-type (wt) protein and to probe the utility of the residues as spectroscopic reporters. A comparative analysis of the fluorescence spectra of PfTIMwt and the two mutant proteins revealed that W168 possesses an unusual, blue-shifted emission (321 nm) and exhibits significant red-edge excitation shift of fluorescence. In contrast, W11 emits at 332 nm, displays no excitation dependence of fluorescence, and behaves like a normal buried chromophore. W168 has a much shorter mean lifetime (2.7 ns) than W11 (4.6 ns). The anomalous fluorescence properties of W168 are abolished on unfolding of the protein in guanidinium chloride (GdmCl) or at low pH. Analysis of the tryptophan environment using a 1.1-A crystal structure established that W168 is rigidly held by a complex network of polar interactions including a strong hydrogen bond from Y164 to the indole NH group. The environment is almost completely polar, suggesting that electrostatic effects determine the unusually low emission wavelength of W168. To our knowledge this is a unique observation of a blue-shifted emission from a tryptophan in a polar environment in the protein. The wild-type and mutant proteins show similar levels of enzymatic activity and secondary and tertiary structure. However, the W11F mutation appreciably destabilizes the protein to unfolding by urea and GdmCl. The fluorescence of W168 is shown to be extremely sensitive to binding of the inhibitor, 2-phosphoglycolic acid.

QSAR of peripheral benzodiazepine receptor ligand 2-phenylimidazo-[1,2-a]pyridine derivatives with physico-chemical parameters.

QSAR of the binding affinities of [2-phenylimidazo[1,2-a]pyridin-3-yl]acetamide derivatives (Fig. 1) with central and peripheral (from cortex and ovary) benzodiazepine receptors has been explored using physico-chemical parameters. Attempt has been made to explore the structural and/or physico-chemical requirements of the compounds that are responsible for the selective action against peripheral benzodiazepine receptors over central ones. The results indicate that the presence of bi-substitution on the carboxamido nitrogen, presence of substitutions at X and Y positions, especially, chloro substitution at X position, and presence of chloro substitution at Z position in presence of lipophilic X and/or Y substitutions increase selectivity for binding affinity with peripheral benzodiazepine receptors over central ones.

QSAR of human factor Xa inhibitor N2-aroylanthranilamides using principal component factor analysis.

Quantitative structure-activity relationship (QSAR) study of human factor Xa inhibitor N2-aroylanthranilamides, recently reported by Yee et al. (J. Med. Chem., 43, 873-882), has been performed using principal component factor analysis as the preprocessing step. The study reveals that presence of electron-donating R2 substituent at the para position (with respect to the amide linkage) is conducive to the binding affinity, whereas a meta R2 substituent decreases the affinity. Again, electron-donating R1 substituents with less bulk and optimum hydrophilic-lipophilic balance (particularly, methyl and methoxy groups) favor the activity. The study further suggests that electron-withdrawing R3 substituents are detrimental for the activity, whereas bulkier R4 substituents (particularly NHSO2Me group) increase the activity.

QSAR with electrotopological state atom index: human factor Xa inhibitor N2-aroylanthranilamides.

Recently, N2-aroylanthranilamides have been reported as novel series of possible anticoagulant drug candidates and the two aryl rings (A and B) have been suggested to interact with S1 and S4 regions, respectively, of human factor Xa (hfXa). In the present effort, quantitative structure-activity relationship (QSAR) of the hfXa binding affinity of 32 N2-aroylanthranilamides have been attempted, in continuation of our previous report on the QSAR analysis of the data set using linear free energy related (LFER) model, with electrotopological state atom (ETSA) index (Kier and Hall, 1991, Adv. Drug Design., 22, 1-38), to explore the atoms/regions of the compounds that modulate the activity comparatively to the greater extent. The univariate and bivariate relations involving the ETSA values of different common atoms of the compounds show importance of the atom nos. 12, 3 and 17 (arbitrary numbering): B ring carbon bearing meta R2 substituents, C ring carbon bearing R4 substituent, and carbonyl oxygen of A ring amide linkage. The importance of atom 12 is suggested to be due to detrimental effects of meta R2 substituents (B ring) on the hfXa binding affinity, which may be owing to interference in the attainment of the proper orientation of the phenyl ring in the S4 site. Atom 3 signifies the impact of R4 substituents (central C ring) on the binding affinity. Again, atom 17 (carbonyl oxygen of A ring amide linkage) has been suggested to form hydrogen bonding with the NH group of the other amide linkage, producing a pseudo ring and thus stabilizing the structure. The relations were improved further using indicator and physicochemical variables and the present results are in good agreement with the previous findings of the Hansch analysis.

Evaluation of probucol as suppressor of ceftizoxime induced lipid peroxidation.

Considering drug induced lipid peroxidation, a possible mediator of drug induced toxicity and exploiting free radical scavenging action of probucol, which is a synthetic antioxidant of therapeutic interest, in vitro effects of the antioxidant on drug induced lipid peroxidation have been studied to explore its possible potential in reducing drug induced toxicity. In the present study, ceftizoxime sodium, a third generation of cephalosporin, has been taken as the representative drug and goat whole blood has been used as the lipid source. The study revealed that probucol could suppress drug induced lipid peroxidation to a significant extent. This provides scope for further study on probucol to evaluate its potential for reducing drug induced toxicity and increasing therapeutic index of drug by possible cotherapy.