Volume 58 (2008): Issue 4 (December 2008)

New series of 2-hydrazino-7,8-dihydro-6H-cyclopenta[5,6] pyrido[2,3-d]pyrimidines and its 1,7,8,9-tetrahydrocyclopenta[5,6]pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine, 1,7,8,9-tetrahydrocyclopenta[5,6]pyrido[2,3-d][1,2,3,4]tetrazolo[4,5-a]pyrimidine, 8,9-dihydro-7H-cyclopenta[5,6]pyrido[2,3-d]imidazolo[1,2-a]pyrimidine, 2-(pyrazol-1-yl)-7,8-dihydro-6H-cyclopenta[5,6]pyrido[2,3-d]pyrimidine derivatives were prepared in order to obtain new compounds with potential anti-inflammatory and analgesic activity and low ulcerogenic effect. The compounds possessing potent anti-inflammatory activity were further tested for their analgesic and ulcerogenic activities. Compounds 3-amino-6-(4-aryl)-9-(4-arylmethylene)-cyclopenta[5,6]pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-5(H)-one (4c), 1-amino-2-methyl-6-(4-aryl)-9-(4-aryl-methylene)-cyclopenta[5,6]pyrido[2,3-d]imidazolo[1,2-a]pyrimidin-5(H)-one (6a), 2-amino-5-(4-aryl)-8-(4-arylmethylene)-cyclopenta[5,6]pyrido-[2,3-d]pyrimidine-4(H)-one (9), 2-(3-amino-5-hydroxypyrazol- 1-yl)-5-(4-aryl)-8-(4-arylmethylene)-cyclopenta[5,6]-pyrido[2,3-d]pyrimidin-4(H)-one (10a) and 3-thioxo-6-(4-aryl)-9-(4-arylmethylene)-cyclopenta[5,6]pyrido[2,3-d]-[1,2,4]triazolo[4,3-a]pyrimidin-5(H)-one (13) showed significant analgesic effects. Compound 2-(3-amino-5-hydroxypyrazol-1-yl)-5-(4-aryl)-8-(4-arylmethylene)-cyclopenta [5,6]pyrido[2,3-d]pyrimidin-4(H)-one (10a) was evaluated as the lead compound having higher anti-inflammatory activity (82.8%) than ibuprofen (79.5%) and lower ulcerogenic effect.

The objective of the present investigation was to reduce the bitterness of artemether (ARM). Microparticles were prepared by the coacervation method using Eudragit E 100 (EE) as polymer and sodium hydroxide solution as nonsolvent for the polymer. A 3² full factorial design was used for optimization wherein the amount of drug (A) and polymer (B) were selected as independent variables and the bitterness score, particle size and drug release at pH, 1.2 and 6.8 were selected as dependent variables. Optimization was carried out using the desirability function. The optimized microparticles batch was characterized by FTIR and DSC. Multiple linear regression analysis revealed that reduced bitterness of ARM can be obtained by controlling the drug release of microparticles at pH 6.8 and increasing the amount of EE. The increase in the amount of polymer leads to reduction in drug release from microparticles at pH > 5 due to its insolubility and thus reduces bitterness. However, the increase in the amount of polymer results in improved dissolution, suggesting improved availability of ARM in stomach. Optimized microparticles prepared using 0.04 g of ARM and 15 mL of 1% (m/V) solution of EE showed complete bitter taste masking with improved drug release at pH 1.2.

The present study describes the synthesis and pharmacological evaluation of 2-substituted-6-(4-acylaminophenyl)-4,5-dihydropyridazin-3(2H)-ones as potent inodilating agents. The synthesis of target compounds 2-4 and 7-11 was achieved by Friedel-Crafts acylation of appropriate anilide derivative with succinic anhydride or methylsuccinic anhydride and subsequent cyclization of intermediary keto acids with various hydrazine derivatives. The newly synthesized pyridazinone derivatives were evaluated for cardiotonic activity using isolated rat atria and for vasorelaxant activity using descending thoracic aortic rings of Wistar rats precontracted with phenylephrine (10^-6 mol L^-1). 6-(4-Methanesulfonamidophenyl)-2-phenyl-4,5-dihydropyridazin-3(2H)-one (7) exhibited significant inodilatory properties and showed vasorelaxant activity in a nanomolar range (IC₅₀ = 0.08 ± 0.01 μmol L^-1).

An acid buffering bioadhesive vaginal (ABBV) gel was developed for the treatment of mixed vaginal infections. Different bioadhesive polymers were evaluated on the basis of their bioadhesive strength, stability and drug release properties. Bioadhesion and release studies showed that guar gum, xanthan gum and hydroxypropyl methylcelullose K4M formed a good combination of bioadhesive polymers to develop the ABBV gel. Monosodium citrate was used as an acid buffering agent to provide acidic pH (4.4). The drugs clotrimazole (antifungal) and metronidazole (antiprotozoal as well as antibacterial) were used in the formulation along with Lactobacillus spores to treat mixed vaginal infections. The ex vivo retention study showed that the bioadhesive polymers hold the gel for 12-13 hours inside the vaginal tube. Results of the in vitro antimicrobial study indicated that the ABBV gel had better antimicrobial action than the commercial intravaginal drug delivery systems and retention was prolonged in an ex vivo retention experiment.

Ca²⁺ accumulation and Ca²⁺ overloading in mitochondria are responsible for the cell abnormality associated with ischemia and reperfusion injury. The present study was aimed at evaluating the efficacy of the Ca²⁺ channel blocker amlodipine on the mitochondrial Ca²⁺ accumulation, mitochondrial antioxidant status and mitochondrial respiratory enzymes in ischemia and reperfusion (I/R) induced liver injury. I/R injury induced mitochondrial damage in rats was assessed in terms of the decrease in activities (p < 0.05) of respiratory marker enzymes (malate dehydrogenase, succinate dehydrogenase and NADH dehydrogenase), mitochondrial antioxidant enzymes (glutathione, superoxide dismutase, catalase), and significant increase (p < 0.05) in the level of lipid peroxidation (LPO) and Ca²⁺ content.

Mitochondrial damage was confirmed by transmission electron microscopic (TEM) examination. Pretreatment with amlodipine effectively counteracted the alteration in mitochondrial enzymes induced by ischemia-reperfusion liver damage. TEM study confirms the restoration of cellular normalcy and the cytoprotective role of amlodipine against I/R induced hepatic injury. On the basis of our findings it may be concluded that amlodipine not only possesses Ca²⁺ channel antagonist properties but it may also reduce the extent of mitochondrial damage by its antioxidant activity.

Condensation of β-amino-α,γ-dicyanocrotononitrile (1) with acetophenone gave 2-amino-4-phenylpenta-1,3-diene-1,1,3-tricarbonitrile (2). The latter product was used in a series of heterocyclization reactions with different reagents such as diazonium salts, hydrazines, hydroxylamines and elemental sulfur to give pyridazine, pyrazole, isoxazole and thiophene derivatives, respectively. On the other hand, it gave pyridine derivatives with aromatic aldehydes folowed by reaction with cyanomethylene reagents. The MIC values for the newly synthesized product were measured against E. coli, B. cereus, B. subtilis and C. albicans.

A series of new 5-(1H-indol-3-yl)methyl-4-(substituted aryl)-2,4-dihydro-3H-1,2,4-triazole-3-thiones (4a-g), 5-(1H-indol-3-yl)methyl-N-(substituted aryl)-1,3,4-oxadiazol-2-amines (5a-g) and 5-(1H-indol-3-yl)methyl-N-(substituted aryl)-1,3,4-thiadiazol-2-amines (6a-g) were prepared by treating 2-(1H-indol-3-yl)acetyl-N-(substituted phenyl) hydrazine carbothioamides (3a-g) with suitable reagents. All the newly synthesized compounds were screened for their anticonvulsant activity in the MES model and were compared with the standard drugs phenytoin sodium and carbamazepine. Out of the twenty-one compounds studied, 4b, 4e, 4f, 5b, 5d, 5g, 6b, 6d and 6e showed comparable MES activity to phenytoin and carbamazepine after 0.5 h. Compound 5b showed to be more potent than carbamazepine after 4 h. Compounds 4a, 4c, 4d, 5a, 5c, 5e, 5f, 6f and 6g showed lower neurotoxicity than phenytoin.

Ternary complexes of meloxicam (ME) (a poorly water soluble anti-inflammatory drug) with hydroxypropyl-β-cyclodextrin (HPβCD) and either a hydrophilic polymer, namely, polyvinyl pyrrolidone (PVP) or a basic amino acid such as L-arginine, were prepared by the spray-drying technique. The solubilizing efficiency, physical properties and dissolution behaviour of each ternary system of ME-HPβCD with either PVP or L-arginine were compared with those of the corresponding binary system of ME-HPβCD. Tablets compressed from the ternary system of ME-HPβCD-L-arginine were compared with plain and commercial tablets. Phase solubility experiments suggested the formation of an inclusion complex of A_L type. Ternary system of ME-HPβCD-L-arginine exhibited a stability constant 30.3 times higher than the binary system of ME-HPβCD, while the ternary system of ME-HPβCD-PVP increased the stability constant 2.2 times only. The prepared complexes were characterized by scanning electron microscopy, differential scanning calorimetry and infra red spectroscopy. Ternary solid complexes indicated the presence of strong interactions between the components. The dissolution behaviour of ME from different ternary complexes was higher than its dissolution from the binary system. Tablets compressed from ternary complexes of ME-HPβCD-L-arginine highly improved drug release compared to plain and commercial tablets.

Twelve new 4-(1H-indol-3-yl)-6-phenyl-1,2,3,4-tetrahydropyrimidin-2-ones/thiones (7-18) have been synthesized by reacting 1-aryl-3-(1H-indol-3-yl)-2-propen-1-one with urea and thiourea in ethanolic potassium hydroxide. Their structures have been confirmed by IR, ¹H NMR and mass spectral data. The compounds were tested for their anti-inflammatory activity. Test results revealed that compounds showed 49.5 to 70.7% anti-inflammatory activity where-as the standard drug ibuprofen showed 86.4% activity at the same oral dose. Four compounds, 4-(1H-indol-3-yl)-6-(4-chlorophenyl)-1,2,3,4-tetrahydropyrimidin-2-one (8), 4-(1H-indol-3-yl)-6-(4-methylphenyl)-1,2,3,4-tetrahydropyrimidin-2-one (10), 4-(1H-indol-3-yl)-6-(4-chlorophenyl)-1,2,3,4-tetrahydropyrimidin-2-thione (14), 4-(1H-indol-3-yl)-6-(4-methylphenyl)-1,2,3,4-tetrahydropyrimidin-2-thione (16), that showed significant anti-inflammatory activity were selected to study their ulcerogenic and lipid peroxidation activities. All tested compounds showed significant reduction in the ulcerogenic potential and lipid peroxidation compared to the standard drug ibuprofen.

Immune suppression resulting from chemoprophylaxis and potential drug interaction were investigated in experimental animals pre-medicated with ampicillin and chloroquine followed by immunization with bovine serum albumin bearing liposomes prepared by the reverse phase evaporation method. The prepared liposomes were evaluated for particle size, entrapment efficiency and in vitro release. Humoral immune response was measured in terms of systemic IgG antibody titre by the ELISA method. The present study showed that 7:3 molar ratio of soya phosphatidylcholine and cholesterol produced liposomes of mean diameter of 235.4 ± 10.3 nm and entrapment efficiency of 41.3 ± 3.2%. Ampicillin significantly (p < 0.05) decreased the antibody titre whereas chloroquine did not reduce the antibody titre significantly. The study will help in programming a new drug management and in characterization of vaccine-drug interaction.