Current Medicinal Chemistry - Volume 15, Issue 16, 2008

Malaria is one of the most prevalent diseases of our planet which claims millions of lives annually. Plasmodium falciparum is the causative agent of majority of the mortality and morbidity associated with malaria particularly in tropical countries. Resistance of the parasite to the currently available chemotherapeutic agents poses a serious threat to human being. Inhibition of P. falciparum dihydrofolate reductase (DHFR) enzyme has been used as one of the strategies in curbing malaria. However, due to mutation in the active-site of the enzyme particularly at 16, 51, 59, 108, and 164 residues, the parasite developed resistance to most of antifolate drugs such as cycloguanil and pyrimethamine. Thus, design of new and potent antimalarial agents which are effective against both wild-type and mutant enzymes is very essential in order to minimize burden of P. falciparum malaria. Computer-aided drug design approaches are playing a crucial role in the design of potential antimalarial drug candidates. In this article, molecular modelling studies based on docking, pharmacophore mapping, QSAR, homology modelling, and quantum chemical studies are reviewed. The importance of these methods in understanding mechanism of drug resistance at a molecular level, and design of antimalarial drug candidates are discussed briefly. The examples mentioned in the review could give insights into the wide range of possibilities of using computer-aided drug design (CADD) methodologies.

cGMP has a short-term effect on smooth muscle tone and a longer-term effect on responses to chronic drug treatment or proliferative signals. cGMP-Phosphodiesterase type 5 (PDE5) hydrolizes cGMP, and the result is smooth muscle contraction. PDE5 is a relatively novel therapeutic target of various diseases, such as erectile dysfunction and pulmonary hypertension. The most intensively examined and marketed PDE5 inhibitor was sildenafil (Viagra) but recently vardenafil (Levitra) and tadalafil (Cialis) were launched with beneficial ADME parameters and PDE5 selectivity. The increasing interest in PDE5 inhibition made it reasonable to collect the available inhibitory data from the scientific literature and set up a structure-activity relationship study. Chemical structures of 438 compounds and their cGMP-PDE5 inhibitory data (IC50) were collected from recently published articles. In this paper physiology, regulation and inhibition of PDE5 (and briefly other PDE-s) are discussed and inhibitors are tabulated by the core structures. Finally, a general QSAR model built from these data is presented. All data used in the QSAR study were summarized in a Supplement (for description please see the online version of the article).

Flavonoids (or bioflavonoids) are naturally occurring compounds, ubiquitous in all vascular plants. These compounds have been considered to possess anti-inflammatory properties, both in vitro and in vivo. Although not fully understood, these health-promoting effects have been mainly related to their interactions with several key enzymes, signaling cascades involving cytokines and regulatory transcription factors, and antioxidant systems. The biological effects of flavonoids will depend not only on these pharmacodynamic features but also on their pharmacokinetics, which are dependent on their chemical structure, administered dose schedule and route of administration. Thus, the therapeutic outcome mediated by flavonoids will result from a complex and interactive network of effects, whose prediction require a deep and integrated knowledge of those pharmacokinetic and pharmacodynamic factors. The aim of the present review is thus to provide an integrated update on the bioavailability and biotransformation of flavonoids and the mechanisms of activity at the molecular, cellular, organ and organism levels that may contribute to their anti-inflammatory effects.

Catalytic activity of certain antibodies was proposed by Linus Pauling for the very first time more than six decades ago. Since then few examples of catalytic antibodies (abzymes) were found in human organism. From late 80's many synthetic abzymes were obtained after immunization by Transition State Analogs (TSA). Another approach is based on functional mimicry of antibody to an active site of an enzyme. Detection of an abzymatic activity requires special immunoassays. This unique strategy can be employed for new methods of drug synthesis, as well as for in vivo therapies. Catalytic antibodies seem to be a promising tool for therapeutic purposes, because of their specifity and stereoselectivity.

Flos Magnoliae (FM, Chinese name: Xin-yi) is one of the most commonly used Chinese medicinal herbs. It has a long history of clinical use for managing rhinitis, sinusitis and headache. More than 20 different FM species have been used clinically, which makes species identification and evaluation of pharmacological effects of individual chemical ingredients difficult. In this review, we have summarized the current knowledge on FM phytochemistry and its bioactivity activities. The bioactive compounds in FM include both lipid and water-soluble components. More than 90% of the essential components of FM species are terpenoids, including monoterpenes and sesquiterpenes. Lignans and neolignans including tetrahydrofurofuran, tetrahydrofuran and aryltetralin are also present in FM species. A small number of water-soluble compounds have been isolated from Magnolia flower buds, including a benzylisoquinoline alkaloid magnoflorine, an ester ethyl-E-p-hydroxyl-cinnamate and a flavonoid biondnoid. A wide range of pharmacological actions of FM have been reported, including anti-allergy, anti-inflammation and anti-microbial activity. The structure-activity relationship analysis revealed the influence of methylation at position 5 on the 3,7-dioxabicyclo-(3,3,0)-octane backbone of six lignans in antagonistic activities against platelet-activating factor. In addition, the trans stereoisomer fargesin had a much lower bioactivity than the cis stereoisomer demethoxyaschantin. Recent studies have been directed towards the isolation of other bioactive compounds. Further studies on FM may help to develop new anti-inflammatory and anti-allergic drugs.

The progress of research on the molecular pathogenesis of liver fibrosis and the consequent discoveries are likely to open new possibilities for therapeutic approaches to the management of this disease in the future. A key step towards this goal is a deeper comprehension of both the complex molecular and cellular mechanisms and the signaling involved in the development of hepatic fibrosis. It is not yet clear, in fact, what role apoptosis, cytokines, oxidants and other molecules play and what relationships exist between them in favouring or delaying the onset of these adverse mechanisms. At present, a unique mechanism is recognized to be the main reason for the cause and development of liver fibrosis: sustained hepatic stellate cell activation and transformation. Therefore, in this review, after considering the cause, development of fibrosis and interrelation between molecular and cellular profibrotic mechanisms, the part played in counteracting both of these actions by some anti-oxidants and anti-fibrotic molecules such as cytokines, prostacyclin and others will be taken into consideration. The gene therapy and the possible therapeutic use of liver stem cells and tissue engineering will also be dealt with briefly. At the moment, however, the efficacy of these novel strategies still needs to be further validated in animal studies and confirmed in clinical trials. Some data that are already available from in vitro and animal studies demonstrating the effectiveness of novel approaches to inhibiting or treating liver fibrosis can only offer moderate hope.

Recent advances have identified the podocyte as a key target in glomerular injury. The podocyte is a highly specialized cell which is responsible for the glomerular permselectivity for proteins in the kidney. Podocyte injury or loss leads to proteinuria. Apoptosis has been shown to contribute to renal cell loss, including loss of podocytes. The most striking feature of the podocyte is its ability to form intricate specialized cell junctions, the slit diaphragm. Slit diaphragm proteins play an important role in podocyte biology, protein permselectivity, cell signalling and disease. This review focuses on recent advances on the understanding of podocyte survival regulation, its relationship to slit diaphragm structure and function, and how this knowledge may affect our therapeutic approach to proteinuric kidney disease.