Design and synthesis of 2-methylthio-3-substituted-5,6-dimethylthieno [2,3-d] pyrimidin-4(3H)-ones as analgesic, anti-inflammatory and antibacterial agents

Pain and inflammation are simultaneous responses in bacterial infections. In current clinical practice, two groups of agents like antibacterial and non-steroidal anti-inflammatory drugs (NSAID's) are prescribed simultaneously. Regrettably, none of the drug possesses these activities in a single component. Exploiting the bioisosterism concept, we have documented that 2-phenyl-3-substituted quinazolines, 2,3-disubstituted quinazolines, 2-methyl-3-substituted quinazolin-4-(3H)-ones and 2-methylthio-3-substituted quinazolin-4-(3H)-ones exhibited good analgesic and anti-inflammatory activities. The present work is an extension of our ongoing efforts towards the development and identification of lead molecules by bioisostere concept, for which we designed some of 2-methylthio-3-substituted-5,6-dimethylthieno[2,3-d] pyrimidin-4(3H)-ones. The title compounds were investigated for analgesic, anti-inflammatory and antibacterial activities. While the test compounds exhibited significant activity, the compounds (6-9) showed more potent analgesic activity, and the compounds (8, 9) showed anti-inflammatory activity comparable to the reference standard diclofenac.     

Antiplasmodial activity of aporphine alkaloids and sesquiterpene lactones from Liriodendron tulipifera L.

Aim of the study

The objective of this study was to isolate and characterize the active constituents of the traditionally used antimalarial plant Liriodendron tulipifera by antiplasmodial-assay guided fractionation.

Materials and methods

Bark and leaves were extracted with solvents of increasing polarity. Fractions were generated using flash chromatography, counter current chromatography and preparative HPLC and subjected to in vitro antiplasmodial and cytotoxicity assays. Active fractions were subjected to further fractionation until pure compounds were isolated, for which the IC₅₀ values were calculated.

Results and discussion

Six known aporphine alkaloids, asimilobine (1), norushinsunine (2), norglaucine (3), liriodenine (4), anonaine (5) and oxoglaucine (6) were found to be responsible for the antiplasmodial activity of the bark. Leaves yielded two known sesquiterpene lactones, peroxyferolide (7) and lipiferolide (8) with antiplasmodial activity. The antiplasmodial activity of (2) (IC₅₀ = 29.6 μg/mL), (3) (IC₅₀ = 22.0 μg/mL), (6) (IC₅₀ = 9.1 μg/mL), (7) (IC₅₀ = 6.2 μg/mL) and (8) (IC₅₀ = 1.8 μg/mL) are reported for the first time.

Conclusion

This work supports the historical use of Liriodendron tulipifera as an antimalarial remedy of the United States and characterizes its antiplasmodial constituents.     

Load-dependent mechanism of nonmuscle myosin 2

Loads on molecular motors regulate and coordinate their function. In a study that directly measures properties of internally strained myosin 2 heads bound to actin, we find that human nonmuscle myosins 2A and 2B show marked load-dependent changes in kinetics of ADP release but not in nucleotide binding. We show that the ADP release rate constant is increased 4-fold by the assisting load on one head and decreased 5-fold (for 2A) or 12-fold (for 2B) by the resisting load on the other. Thus these myosins, especially 2B, have marked mechanosensitivity of product release. By regulating the actin attachment of myosin heads, this provides a basis for energy-efficient tension maintenance without obstructing cellular contractility driven by other motors such as smooth muscle myosin. Whereas forward load accelerates the cycle of interaction with actin, resistive load increases duty ratio to favor tension maintenance by two-headed attachment.     

Ion channels as important targets for antiepileptic drug design

Ion channels have a critical role in the function of the nervous system, where they instigate and conduct nerve impulses by asserting control over the voltage potential across the plasma membrane. Propagation of electrical impulses occurs by opening of voltage-gated ion channels. Ion channel blockers prevent this from occurring, and can therefore be used in the treatment of central nervous system disorders and neuropathic pain. Recent identification of ion channel gene mutations in Mendelian epilepsies suggests that genetically driven neuronal hyperexcitability plays an important role in epileptogenesis. Studies with animal seizure models have indicated that changes in temporal and spatial expression of voltage-gated sodium channels may be important in the pathology of epilepsy. This paper is aimed at elucidating the organization of the ion channels and covers a review on the antiepileptic drugs, both established and currently under development targeted to the ion channels in order to bring about effective seizure control.     

Glycaemic control by Casearia esculenta--a short duration study in albino rats

An aqueous extract of Casearia esculenta was found to lower blood glucose in basal conditions and after a glucose load in normal rats. Maximum reduction in blood glucose was observed between 2-3 h at a dose level of 200 and 300 mg/kg body weight. C. esculenta extract was also found to reduce the blood sugar level in streptozotocin--induced diabetic rats. Oral administration of the extract significantly reduced the blood sugar in streptozotocin induced diabetic rats for 15 days. The extract was also found to reduce the increased plasma thiobarbituric acid reactive substances (TBARS), blood urea and improvement in body weight reduction induced by streptozotocin injection. These results indicate that C. esculenta extracts are able to ameliorate biochemical changes induced by streptozotocin in diabetic rats.     

Discovery of N-(2,6-dimethylphenyl)-substituted semicarbazones as anticonvulsants: hybrid pharmacophore-based design

Epilepsy is the most common primary neurological disorder known. In the past decade, various aryl semicarbazones have been designed that were structurally dissimilar from many common anticonvulsants containing the dicarboximide function (CONRCO), which may contribute to toxic side effects. In the present work various N4-(2,6-dimethylphenyl) semicarbazones were designed as pharmacophore hybrids between the aryl semicarbazones and ameltolide. A three-dimensional four-point pharmacophore model was developed for anticonvulsants, and the title compounds were found to match with ralitoline. All of the compounds exhibited anticonvulsant activity in the maximal electroshock test when administered by both intraperitoneal and oral routes. Compound N1-(2,6-dimethylphenyl)-N4-(2-hydroxybenzaldehyde) semicarbazone (9) emerged as a prototype with wide spectrum anticonvulsant agent active in five models of seizure with no neurotoxicity and hepatotoxicity. Compound 9 increased the 4-aminobutyric acid (GABA) level by 118% and inhibited the GABA transaminase enzyme both in vitro and ex vivo.     

Modulating role of 'Saptarangi' (Casearia esculenta) on membrane bound ATPase in streptozotocin diabetic rats

We have studied the activities of adenosine triphosphatase (Na+/K+ATPase, Mg2+ATPase, Ca2+ATPase and Total ATPase) in erythrocyte, liver, kidney and cardiac tissues of control and Casearia esculenta treated streptozotocin (STZ) diabetic rats. The activity of Na+/K+ATPase plays a central role in the regulation of intra and extra cellular homeostasis and alteration of this transport system is thought to be linked to several complications of diabetes mellitus. An Mg2+ dependent ATPase activity is responsible for controlling the energy requiring process in cells whereas Ca2+ATPase is responsible for the signal transduction pathways and membrane fluidity. Activities of these enzymes were significantly altered (p < 0.05) in STZ diabetic rats. Oral administration of C. esculenta root extract for a period of 45 days resulted in significant (p < 0.05) reversal of these enzymes' activities to near normal. Thus the results suggest that C. esculenta protects the membrane integrity and functional status in STZ diabetic rats.     

Synthesis and pharmacological evaluation of 3‐(4‐chloro phenyl)‐2‐substituted‐3H‐quinazolin‐4‐ones as analgesic and anti‐inflammatory agents

A new series of 3‐(4‐chloro phenyl)‐2‐substituted‐3H‐quinazolin‐4‐ones were synthesized by reacting the amino group of 2‐hydrazino‐3‐(4‐chloro phenyl)‐3H‐quinazolin‐4‐one with different aldehydes and ketones. The compounds were investigated for their analgesic activity in albino mice, and for their anti‐inflammatory and ulcerogenic activities in Wistar rats. All test compounds exhibited analgesic and anti‐inflammatory activities. Compound VA2 (2‐(1‐ethylpropylidene‐hydrazino)‐3‐(4‐chloro phenyl)‐3H‐quinazolin‐4‐one) showed moderately more potent analgesic activity and compound VA3 (2‐(1‐methylbutylidene‐hydrazino)‐3‐(4‐chlorophenyl)‐3H‐quinazolin‐4‐one) showed moderately more potent anti‐inflammatory activity when compared with the reference standard, diclofenac sodium. The test compounds showed only mild ulcerogenic side effects when compared with aspirin. Drug Dev Res 69: 226–233, 2008 ©2008 Wiley‐Liss, Inc.