Medicinal Chemistry - Volume 5, Issue 6, 2009

3-bromopyruvate (3-BrPA), a pyruvate analog recently proposed as a possible anticancer drug, was investigated in relation to its capacity to inhibit energy production in fractions obtained from normal cells (rat hepatocytes) and in isolated rat thymocytes. Findings were that main targets of the drug were glyceraldehyde 3-phosphate dehydrogenase, and not hexokinase as suggested for hepatoma cells, and succinate -driven ATP synthesis. Consistently with the above findings, in the normal cells studied (thymocytes) the drug elicited an important fall in ATP levels. The significance of the present findings in concern with a possible therapeutic usefulness of the drug is discussed.

The objective of this study was to synthesize derivatives of the anti-HIV drug stavudine (d4T) with more favourable physicochemical properties for transdermal delivery in an effort to increase transdermal penetration of stavudine and thus reduce the severe side effects associated with the dose-dependent oral therapy. The synthesis, hydrolytic stability, and in vitro human skin permeation flux of a series of novel methoxypoly(ethylene glycol) (MPEG) carbonates of stavudine are reported. The carbonates were synthesized in a two-step process by coupling the MPEG promoiety of various chain lengths to C-5' of d4T. In kinetic studies the carbonates proved to be markedly stable in weakly acidic phosphate medium (pH 5.0) with half-lives ranging from 16 to 58 days. The aqueous solubility increased as the ethylene oxide chain lengthened. However, there was no significant increase in the estimated solubility in octanol. In vitro in the phosphate buffer (200 mM; pH 5.0) almost all carbonates permeate the human skin. However, the most effective penetrant, the derivative with 3 ethylene oxide units in the side chain, exhibited a flux of 26.1 nmol/cm2/h as compared to 59.15 nmol/cm2/h of the parent drug stavudine. Thus, no permeation enhancement was observed during this study.

In prosecution of an anti-Flaviviridae project a new series of variously substituted 2-diphenyl-benzimidazoles were synthesized and tested in vitro for antiviral and antiproliferative activities. Compounds were tested in cell-based assays against viruses representative of: i) two of the three genera of the Flaviviridae family, i.e. Flaviviruses and Pestiviruses; ii) other RNA virus families, such as Retroviridae, Picornaviridae, Paramyxoviridae, Rhabdoviridae and Reoviridae; iii) two DNA virus families (Herpesviridae and Poxviridae). The 5- Acetyl-2-(4'-nitrobiphenyl-4-yl)-1H-benzimidazole (24) emerged as potent active lead compound against Yellow Fever Virus (a Flavivirus) (EC50= 0.5 μM) and CVB-2 at 1 μM and was not cytotoxic, whereas the other title benzimidazoles showed no antiviral activity at concentrations not cytotoxic for the resting cell monolayers. Among the examined series, the most cytotoxic derivatives (11,12,14,16,18,19,20,21,23,25-30) against mock-infected MT-4 cells (CC50 <8.0 μM) were evaluated against a panel of human cell lines derived from haematological and solid tumours, using 6-mercaptopurine (6-MP) and etoposide as reference drugs. In particular, compounds 26 and 28 showed a similar potency of 6-MP and etoposide.

Many bacteria grow on surfaces forming biofilms but often high dosages of antibiotics can not clear infectious biofilms. Biofilms are controlled by a process called quorum-sensing triggered by species-specific, small, diffusible autoinducers (N-acyl homoserine lactones (AHL), small peptides or a furanosyl borate diester). Several herbal, animal and microbial extracts possess quorum-quenching activity but only few active compounds and synthetic analogues are known. However, quorum-sensing seems not to be the only way to control biofilms. Bacteria have mechanisms to dissolve their biofilms and return to planktonic lifestyle. Only few compounds responsible for the signalling of these processes are known but may open a completely novel line of biofilm control. Furthermore, controlling the attachment of bacterial by inhibiting the formation of pili is another option and some inhibitors have already been characterized. In this article different approaches to control bacterial biofilms are discussed together with the balance between biofilm formation and virulence.

Helicobacter pylori infection is the main cause of gastritis and gastroduodenal ulcer disease, and is associated with gastric cancer. In order to develop new potential anti-Helicobacter pylori candidates, we have investigated the antimicrobial activity of some 2-substituted-5-nitroheterocycles against H. pylori. The anti-Helicobacter pylori activity of selected compounds along with commercially available antibacterial metronidazole was evaluated by comparing the inhibition zone diameters determined using the paper disc diffusion bioassay. The compounds that exhibited strong anti-H. pylori activity at concentration of 8-32 μg/disc (average of inhibition zone >20 mm) were further tested against 20 clinical isolates of H. pylori at lower concentrations. In general, we have identified a series of 5-nitroheterocyles including nitrofurans, nitrothiophenes and nitroimidazoles bearing a carboxaldehyde thiosemicarbazone or 2-substituted-1,3,4- thiadiazole residues in the 2-position of the 5-nitroheteroaryl ring as potent anti- Helicobacter pylori agents. It was found that chloro-/ amino-/ mercapto-substituted 1,3,4-thiadiazole moiety attached to 5-nitroheteroaryl ring served as promising C-2 substituents for 2-substituted-5-nitroheterocycles. The Structure-activity relationship of this series indicates that both the structure of the nitroaryl scaffold and the C-2 attached residue have dramatic impact on anti-Helicobacter pylori activity.

Lipopolysaccharides (LPS, endotoxins) are main constituents of the outer membranes of Gram-negative bacteria, with the ‘endotoxic principle’ lipid A anchoring LPS into the membrane. When LPS is removed from the bacteria by the action of the immune system or simply by cell dividing, it may interact strongly with immunocompetent cells such as mononuclear cells. This interaction may lead, depending on the LPS concentration, to beneficial (at low) or pathophysiological (at high concentrations) reactions, the latter frequently causing the septic shock syndrome. There is a variety of endogenous LPS-binding proteins. To this class belong lactoferrin (LF) and hemoglobin (Hb), which have been shown to suppress and enhance the LPS-induced cytokine secretion in mononuclear cells, respectively. To elucidate the interaction mechanisms of endotoxins with these proteins, we have investigated in an infrared reflection-absorption spectroscopy (IRRAS) study the interaction of LPS or lipid A monolayers at the air/water interface with LF and Hb proteins, injected into the aqueous subphase. The data are clearly indicative of completely different interaction mechanisms of the endotoxins with the proteins, with the LF acting only at the LPS backbone, whereas Hb incorporates into the lipid monolayer. These data allow an understanding of the different reactivities in the biomedicinal systems.

Eight new organotin (IV) derivatives of general formula [N(CH2CH2O)3GeCH(R1)CH2COO]4-nSnR2 n, where n = 2, R2 = C2H5 (1-5); R1 = CH3 (1); C6H5 (2); p-CH3C6H4 (3); p-FC6H4(4); p-CH3OC6H4 (5) and n = 3, R2 = CH2C6H5 (6- 8), R1 = CH3 (6); C6H5 (7); p-CH3C6H4 (8) have been synthesized by the reaction of di- or tri-organotin chloride with the corresponding germatranyl (substituted) propionic acid in the appropriate mole ratios using triethylamine as a base. The synthesized compounds were characterized by various spectroscopic techniques such as IR, multi-nuclear (1H, 13C, 119Sn) NMR, 119mSn Mossbauer, along with elemental analyses. They were also screened for in vitro anti-leishmanial activity against promastigotes of leishmania donovani and found some encouraging results.

Cancer is one of the life threatening diseases and the development of novel anticancer molecules is limited by many reasons. In the present investigation, some novel benzo[a]phenazine-5-sulfonic acid derivatives as DNA intercalator was designed with optimized pharmacokinetic features for cancer treatment. The compounds with desired pharmcokinetic profile were synthesized and structurally characterized. Cytotoxic activity study against HL-60 tumor cell lines shows that 10-dimethyl carboxamido derivative of benzo[a]phenazine-5-sulfonic acid is found to be the most active in the series with cytotoxic activity (IC50 = 19 μM) comparable to cisplatin (IC50 = 7 μM). The study concluded that the novel benzo[a]phenazine-5-sulfonic acid derivatives were found to have enhanced DNA binding affinity and exhibited significant activity in vitro against HL-60 cell lines. This work will also guide for further development of effective DNA intercalators for cancer treatment.

A series of 2-methyl-N-substituted-benzimidazoles, bearing hydroxypyrrolidinon-5-yl or hydroxypyrrolidin-2- yl, 2,3:5,6-di-O-isopropylidene-α-D-mannofuranoside, 2,3,5,6-tetrahydroxy-α-D-mannofuranoside, 1:2,5:6-di-O-isopropylidene- α-D-gluco-furanose,3-O-benzyl-6,7-dideoxy-1:2-O-isopropylidene-α-D-xylo-heptofuranos-5-ulose, 3-O-benzyl- 6,7-dideoxy-1,2-dihydroxy-α-D-xylo-heptofuranos-5-ulose, 1,2,5,6-tetrahydroxy-α-D-glucofuranose sugar moieties, were obtained in good yields from 2-methyl N-(trichloroacetamidomethyl)benzimidazole as a donor and carbohydrate residues as acceptor precursors in the presence of catalytic amount of trimethylsilyl trifluoromethanesulfonate (TMSOTf) as Lewis acid. Compounds 6, 7, 10, 13, 15, and 16 showed significant anti-inflammatory and analgesic activities.

A quantitative-structure activity relationship (QSAR) study has been made on two different series of sodium channel blockers – namely, a series of 3-(4-phenoxyphenyl)pyrazoles and a series of 2-alkyl-4-arylimidazoles – and a series of potassium channel blockers that comprises of khellinone derivatives, which act on voltage-gated K+ channels Kv1.3. In both the cases – the inhibition of Na+ channels or the inhibition of K+ channels – the significant correlations were obtained between the inhibition potencies and the hydrophobic properties of the compounds. This led to suggest that the hydrophobic property of the compounds is a major determining factor of the Na+/ K+ channel blocking activity and that the compounds might elicit their effects through the hydrophobic interactions with the receptors.

The synthesis and pharmacological activities of anthraquinone-ibuprofen prodrugs for finding new antiinflammatory drugs specifically targeting osseous tissues were studied. Two hydrolytically activated anti-inflammatory prodrugs containing anthraquinone moiety and ibuprofen moiety were designed and synthesized. Rhein was chosen as bone-targeting agent and potentially active drug, which was linked chemically with ibuprofen through glycol ester as bone-targeting anti-inflammatory prodrugs. The chemical structures of the new compounds were confirmed by IR, 1H NMR, 13C NMR, MS and elemental analysis. The studies of bioactivities demonstrated that both prodrugs showed significant binding capability to hydroxyapatite (HAP), the major component of bone, and were hydrolytically activated under physiological conditions in vitro and better anti-inflammatory activity in vivo.

Previous studies presented evidence that plants contain antioxidants that have free radical-scavenging properties. Overproduction of free radicals leads to oxidative stress, a factor associated with a variety of diseases, such as diabetes. Cytochrome P450 2E1 enzymes (CYP2E1) are involved in drug metabolism in the liver and metabolism of DNAreaction generating intra-mitochondrial ROS, which leads to micro- and macro-vascular pathology in diabetes. Plantbased chemicals can affect CYP2E1 enzymes and related defense mechanisms, possibly leading to protection against oxidative stress. We investigated the effect of Solanum torvum (ST) extracts on the inhibition of CYP2E1 activity in human liver microsomes. ST extract was analyzed for antioxidant activity by the ABTS method. Polyphenolic compounds were measured by the total phenol content using the Folin-Ciocalteau reagent. Flavonoid and tannin content were analyzed by standard methods. Oxidative stress was evaluated by measuring lipid peroxidation by TBARS and superoxide anion scavenging levels in plasma from diabetic patients. Results showed that 10 mg/ml of ST had CYP2E1 catalytic inhibiting activity (57.16 %). The IC50 value of CYP2E1 catalytic inhibiting activity level was 5.14 mg/ml by concentration in a dependent manner. One gram of concentrated ST extract had an antioxidant activity index of 3.68 mg of trolox and 360.53 mg of ascorbic acid equivalent. Effects on free radical-scavenging, as measured by TBARS and superoxide anion, showed IC50 values of 20.60 and 10.26 μg/ml, respectively. Polyphenolic compounds found included phenol, flavonoid and tannin, measuring 160.30, 104.36 and 65.91 mg/g, respectively. These results imply that ST is a natural source of polyphenolic antioxidants, which have cytochrome P450 2E1 enzyme inhibiting and free radical scavenging properties, as related to lipid peroxidation and superoxide anion activity. ST could potentially be used for reducing oxidative stress in diabetes. Study for usage as a conventional medicine, including dosage and chronic toxicity in humans, should be pursued.