Medicinal Chemistry - Volume 2, Issue 4, 2006

Steroidogenic enzyme type 3 17β-hydroxysteroid dehydrogenase (17β-HSD) is an important therapeutic target for androgen-sensitive diseases. This enzyme selectively reduces the C17 ketone of 4-androstene-3,17-dione (Δ4-dione), thus producing testosterone (T) using NADPH as cofactor. Our group previously synthesized hybrid (estradiol/adenosine) inhibitors that successfully inhibit the biosynthesis of the potent estrogen estradiol by type 1 17β-HSD. To similarly lower the level of the potent androgen testosterone, inhibitors of type 3 17β-HSD were designed and synthesized applying the same hybrid (substrate/cofactor) strategy. Two chemical approaches were developed to join the three components of the bisubstrate inhibitor (the substrate Δ4-dione, an alkyl spacer and the cofactor moiety adenosine). An alkylation in the α position of steroidal 17-ketone or a cross-metathesis was used as a key step to efficiently join the substrate and the alkyl spacer, whereas an esterification was employed to link the spacer to adenosine. An enzymatic assay in homogenated HEK-293 cells overexpressing type 3 17β-HSD revealed that the best inhibitors of that series are those bearing an alkyl side-chain spacer of 11 or 12 methylenes: inhibition of 69 and 78% at 1 μM were respectively observed. As expected, these bisubstrate inhibitors were less potent in intact cells than in homogenated cells. However, both enzymatic assays revealed that the strategy of substrate/cofactor dual inhibitors seems to work for type 3 17β-HSD, although the inhibitors designed have not been optimized yet.

The trypsin-like serine protease factor Xa (fXa) is located at the convergence point of the intrinsic and extrinsic coagulation cascade, and therefore has emerged as an attractive target for the design of novel anticoagulants. During the development of substrate-analogue urokinase inhibitors we have found that the protection of the P3-DSer side chain leads to a scaffold of potent fXa inhibitors with the general structure R1-SO2-DSer(R2)-Gly-4-amidinobenzylamide. The first lead (3) with an N-terminal benzylsulfonyl group and DSer(tBu) as P3 residue inhibits human fXa with a Ki of 14 nM. A variety of derivatives with modified P4, P3, and P2 residues have been investigated in terms of inhibition of fXa and related proteases and for their anticoagulant potency and elimination behaviour. Most inhibitors were rapidly cleared from the circulation of rats. However, compound 48 (Ki = 3.5 nM), one of the most potent and selective inhibitors containing a DArg as P3 residue was relatively slowly eliminated (t_ ≈ 1h). Inhibitor 48 doubled clotting times in human plasma at 0.32 μM (aPTT) and 0.28 μM (PT), and is approximately 10-fold more potent than the reference fXa inhibitor DX-9065a in the inhibition of the prothrombinase complex. The structures of two inhibitors in complex with human fXa were solved by X-ray crystallography.

A lanosterol 14α-demethylase inhibitors of chromene series were subjected to classical quantitative structural activity relationship studies. Apart from the indicator variables encoding for different group contribution, there are various physico-chemical descriptors like steric, thermodynamic and electronic parameters, which were applied to explore the structural requirements for inhibition of enzyme. Multiple linear regression analysis shows that substituents on the appended alkylated ether and the carbon chain length, which should not be more than six at R3 and R1 positions in the parent nucleus, are essential to modulate the activity. Electronic parameters such as highest occupied molecular orbital energy and dipole dipole energy have been found to play an important contribution for biological activity. From the orientation or distribution of the total molecular structures in 3D space, it was assessed that Principal Moments of Inertia at X-axis is detrimental for fungal inhibitory activity. Thus validated models bring important structural insights to aid the design of potent lanosterol 14α-demethylase inhibitors prior to their synthesis.

Bisdioxopiperazines, including ICRF-154 and razoxane (ICRF-159, Raz), are a family of anticancer agents developed in the UK, specifically targeting neoplastic metastases. Two other bisdioxopiperazine derivatives, probimane (Pro) and MST-16, were synthesized at the Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China. In order to determine the similarities and differences between these agents in medical chemistry, we evaluated the anti-tumor and anti-metastatic effects of Pro and MST-16 in vitro and in vivo against a number of human tumor cell lines and one of murine origin (Lewis lung carcinoma, LLC), and one human tumor xenograft (LAX-83) in nude mice. Our results show that Pro was cytotoxic to human tumor cell lines in vitro (IC50 < 50 μM for 48 h), approximately 3 to 20- fold more than MST-16. Pro and MST-16 manifested more prolonged cytotoxicity than some other first-line anticancer drugs including 5-fluorouacil, vincristine and doxorubicin, and maintain their cytotoxic effects for 4 days in vitro. In animal experiments, Pro and Raz were active against primary tumor growth (35-50 %) and significantly inhibited pulmonary metastasis of LLC (inhibition > 90 %) at dosage below LD5. Both Raz and Pro were effective in administration schedules of 1, 5 and 9 days. Both Raz (25-32 %) and Pro (55-60 %) caused statistically significant inhibition of the growth of LAX 83 (a human lung adeno-carcinoma xenograft) in nude mice. In this model, Pro was more effective against LAX83 than Raz at equitoxic dosages. These findings suggest that Pro is active against more categories of tumors both in vivo and in vitro, which in some circumstances may make it superior to the currently-used anticancer bisdioxopiperazines, including razoxane and MST- 16.

A new benzophenone O-glucoside neoannulatophenonoside (1) together with the known pinocembrin-7-Oglucoside were isolated from the aerial parts of Hyperium annulatum Moris (Guttiferae). The former was identified as 3',5',6-trihydroxy-4-methoxybenzophenone-2-O- β-D-glucopyranoside by means of chemical and physical evidence. The cytoprotective effects of the new compound together with the previously isolated from this species hypericophenonoside (2), annulatophenone (3), annulatophenonoside (4), acetylannulatophenonoside (5) and 1,3,7-trihydroxyxanthone (6) were evaluated in a model of epirubicin-induced cellular toxicity in K-562 cells. While the benzophenone O-glycosides 1, 2, 4 and 5 exerted substantial cytoprotective effects against the epirubicin cytotoxicity in K-562 cells the aglycones 3 and 6 lacked any significant cytoprotective activity. Biochemical investigations aimed at evaluating the free-radical scavenging activity of the tested compounds as well as their effects on the cellular glutathione stores were carried out as well, aiming at unravelling the mechanisms of cytoprotection. Finally, the ability of 1, 4 and 5 to ameliorate epirubicin-induced anticlonogenic effects on bone marrow cells colony forming units, in vitro were also evaluated. Taken together, the experimental data indicate that the benzophenone glycosides isolated from H. annulatum have a substantial cytoprotective potential against the toxic effects induced by epirubicin and necessitates further detailed pharmacological evaluation of these compounds as possible chemoprotective/radioprotective agents.

The fundamental physico-chemical parameters of sertraline, a potent selective serotonin reuptake inhibitor and reference compound in the development of new antidepressive agents, were determined. The thermodynamic solubility of the hydrochloride salt (S = 4.24 ± 0.02 mg/ml) and the free base form (S ≈ 0.002 mg/ml) was measured by the saturation shake-flask method. The co-solvent technique in methanol/water mixtures and the Yasuda-Shedlovsky extrapolation were applied for the determination of the dissociation constant (pKa = 9.16 ± 0.02). The partition of sertraline was studied in octanol/water and alkane/water systems determining the logPoct and logPch values by potentiometric and shake-flask methods, respectively. These experimental data were used to interpret the excellent pharmacokinetic properties of the molecule. The high lipophilicity value (logPoct =4.30 ± 0.01) of the nonionised form confirms the good absorption and distribution in the body. However, the good brain penetration can better be explained with the lack of polar interactions evidenced here by the zero ΔlogP (logPoct - logPch) value of sertraline.

Cyclosporin-A (CsA) is often used in the treatment of nephrotic syndrome. The effectiveness of CsA and the value of C2 blood levels in the treatment of nephrotic syndrome, due to various glomerular diseases, were studied. Forty-two nephrotic patients (M/F 21/21), with well-preserved renal function (creatinine clearance 87± 20ml/min) were included in the study. The original diagnoses were minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), membranous nephropathy (MN), IgA nephropathy (IgAN), and lupus nephritis (LN). All patients were treated with prednisolone and CsA for 24 months. Cyclosporin-A C0 and C2 blood levels were determined at regular intervals. Remission of the nephrotic syndrome was observed in all patients with MCD, IgAN and LN, in 75% with FSGS and in 83%with MN. Relapses were observed in some patients with MCD (25%) and MN (36%). The C0 levels were 93± 15 ng/ml and the corresponding C2 levels were 498± 110 ng/ml. However, significantly lower (340± 83 ng/ml) or higher (680± 127 ng/ml) to the average C2 levels were found in 6 patients (14%). No relation of C0 and C2 levels with the remission and relapse rate of the nephrotic syndrome and with renal function impairment was observed. Small doses of CsA with prednisolone are effective in the treatment of nephrotic syndrome. Although an individual variation of C2 was observed for the same target C0 levels, no relation of C2 levels was found with the remission or relapse rate of the nephrotic syndrome.

The surface loops of proteins and active peptides are implicated in the activation of biological responses upon recognition by enzymes and receptors. Obviously, it is of interest to investigate these loops as potential leads for drug discovery. Currently, there is an urgent need for novel, general, and conformationally definite cyclic peptidomimetic scaffolds capable to mimic small portions of the protein surface. In this respect, 13-membered ring peptidomimetics can be considered privileged structures, since they represent the smallest possible systems that can retain all of the features of organized protein structures, such as single H-bonded alfa-helix loops and different kind of turns. In the present work, we report a novel family of 13-membered ring cyclic peptidomimetics based on a minimal PMRI (partially modified retro-inverse) peptide strategy; in particular, we describe the synthesis and the conformational analysis of a representative member of the family. These scaffolds have been designed to permit easy introduction in a combinatorial fashion of a range of pharmacophores that possess a diversity of structure, function, and 3D disposition.

Activation by human cytochrome P450 1A2 (hCYP1A2) of heterocyclic amines is assumed to trigger of a number of carcinogenic processes. In this work, a group of natural inhibitors of human cytochrome P450 1A2 reported in literature has been theoretically analysed. These consist of flavone hydroxylated derivatives, natural compounds that exist in plants and associated products. Different theoretical/computational tools were used to describe the specific molecular interactions between these compounds and hCYP1A2. Based on this analysis, a method is proposed for helping the selection of specific molecular features that enhance protein-inhibitor interaction.

Acting as a redox switch, folic acid (1) might be a promising iron modulator to protect cellular machinery against oxidative stress and iron overload. The vitamin 1 can directly control the iron concentration by oxidizing it even if present in chelated forms. In addition, during its role as a reducing agent for the biologically relevant reactive oxygen species (ROS), it furnishes 6-formyl pterin. This folate-derived intermediate possesses a stronger Fe2+-oxidizing capacity than 1. Thus, compound 1 can reduce the iron toxicity in two ways. Although, the Fe2+-oxidizing capacity is nullified in the presence of a strong biological reductant like ascorbic acid, this property may play a predominant role during pathogenesis when the cellular ascorbic acid levels deplete significantly. The iron-modulatory property of 1 was also confirmed with the L929 mouse fibroblast cell line.

Antituberculosis activity of several 5-(4-aminophenyl)-4-alkyl/aryl-2,4-dihydro-3H-1,2,4-triazole-3-thiones (1- 9) and their thiourea derivatives (10-31) were screened for their antimycobacterial activities against Mycobacterium tuberculosis H37Rv using the BACTEC 460 radiometric system. Of the synthesized compounds, 10-12, 30 were the most active derivatives exhibiting more than 90 % inhibition of mycobacterial growth at 12.5 μg/mL. Structure-activity relationships study was performed for the given series by using the Electronic-Topological Method combined with Neural Networks (ETM-NN). A system of prognosis was developed as the result of training associative neural network (ASNN) using weights of pharmacophoric fragments as descriptors. Descriptors were calculated by the projection of ETM compound and pharmacophoric fragments on the elements of Kohonen's self-organizing maps (SOM). From the detailed analysis of all compounds under study, the necessary requirements for a compound to possess antituberculosis activity were formulated. The analysis have shown that any requirements violation for a molecule implies a considerable decrease or even complete loss of its activity.

Introduction: Acute pancreatitis is a disease involving pro-inflammatory mediators. Two complex and multifactorial pathogenetic ways lead to edematous or necrotizing pancreatitis. The course of the disease is thought to be the consequence of an acute inflammatory response. AIM: The authors examined the impact of Escherichia coli LPS on the acute cerulein pancreatitis in rats. Methods: The study was performed on rats using the ceruleine pancreatitis model. The activation status of polymorphonuclear cells, blood IL-6 concentration, oxidative stress parameters, pancreatic enzymes concentration and microscopic alterations were determined at 5th and 9th h observations. Results: In acute pancreatitis and acute pancreatitis with LPS groups, the peripheral polymorphonuclear cells activity was lower than in control one. Authors noticed the same neutrophil activation in acute pancreatitis after lipopolysaccharide administration although the peripheral blood polymorphonuclear cells count was significantly higher at the 9th h observation. LPS neither changed the oxidative stress within pancreatic gland, nor amylase or serum lipase activity. LPS given to acute pancreatitis animals resulted in significant increase of serum IL-6 concentration at 5th observation turning normal after 9th h. Conclusions: Collected data supports thesis of early polymorphonuclear cells involvement in acute pancreatitis and oxidative stress evidence in pancreatic parenchyma. However, results did not reveal that administration of LPS amplified inflammatory response during the course of acute pancreatitis.

Retinoids have been investigated for their therapeutic potential for the past 3 decades. They have a reputation for being both beneficial in the treatment of several diseases and detrimental due to toxic and/or teratogenic side effects. The purpose of this review is to highlight retinoids that are currently used in the clinic. We also discuss their mechanisms of action and research strategies to develop new and safer retinoid-based therapies.