Design of multifunctional compounds for cardiovascular disease: from natural scaffolds to "classical" multitarget approach.

Cardiovascular disease represents the main cause of death worldwide. Novel therapies to reduce elevated blood pressure and treat resistant hypertension, to consequently reduce the associated cardiovascular risk factors, are still required. Among the different strategies commonly used in medicinal chemistry to develop new molecules, the synthesis of multitarget/hybrid compounds combining two or more pharmacophore groups targeting simultaneously selected factors involved in cardiovascular diseases, has gained increasing interest. This review will focus on the most recent literature on multifunctional cardiovascular drugs, paying particular attention on hybrid compounds bearing natural scaffolds, considering that compounds derived from medicinal extracts are generally appealing for the medicinal chemist as they often bear the so-called "privileged structures". Moreover, taking into account many excellent reviews dealing with multitarget cardiovascular drugs published in the last few years, mainly devoted to RAAS inhibition and/or NO donors hybrid drugs, herein the most significant results obtained and the benefits and limitations of these approaches will be highlighted.

Acetylcholinesterase inhibitors: SAR and kinetic studies on omega-[N-methyl-N-(3-alkylcarbamoyloxyphenyl)methyl]aminoalkoxyaryl derivatives.

In this work, we further investigated a class of carbamic cholinesterase inhibitors introduced in a previous paper (Rampa et al. J. Med. Chem. 1998, 41, 3976). Some new omega-[N-methyl-N-(3-alkylcarbamoyloxyphenyl)methyl]aminoalkoxyaryl analogues were designed, synthesized, and evaluated for their inhibitory activity against both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). The structure of the lead compound (xanthostigmine) was systematically varied with the aim to optimize the different parts of the molecule. Moreover, such a structure-activity relationships (SAR) study was integrated with a kinetic analysis of the mechanism of AChE inhibition for two representative compounds. The structural modifications lead to a compound (12b) showing an IC(50) value for the AChE inhibition of 0.32 +/- 0.09 nM and to a group of BuChE inhibitors also active at the nanomolar level, the most potent of which (15d) was characterized by an IC(50) value of 3.3 +/- 0.4 nM. The kinetic analysis allowed for clarification of the role played by different molecular moieties with regard to the rate of AChE carbamoylation and the duration of inhibition. On the basis of the results presented here, it was concluded that the cholinesterase inhibitors of this class possess promising characteristics in view of a potential development as drugs for the treatment of Alzheimer's disease.

A new class of nonsteroidal aromatase inhibitors: design and synthesis of chromone and xanthone derivatives and inhibition of the P450 enzymes aromatase and 17 alpha-hydroxylase/C17,20-lyase.

Aromatase (P450arom) is a target of pharmacological interest for the treatment of breast cancer. In this paper, we report the design, synthesis, and in vitro biological evaluation of a series of new (di)benzopyranone-based inhibitors of this enzyme. The design of the new compounds was guided by a CoMFA model previously developed for a series of nonsteroidal aromatase inhibitors. Both the chromone and the xanthone nuclei were taken as molecular skeletons, and the functions supposed to be critical for binding to the aromatase active site - a heterocyclic ring (imidazole or 1,3,4-triazole) linked to the aromatic moiety by a methylene unit and an H-bond accepting function (CN, NO(2), Br) located on the aromatic ring at a suitable distance from the heterocyclic nitrogen carrying the lone pair--were attached to them. The chromone, xanthone, and flavone derivatives were prepared by conventional synthetic methods from the appropriate methyl analogues. Aromatase inhibitory activities were determined by the method of Thompson and Siiteri, using human placental microsomes and [1 beta,2 beta-(3)H]testosterone as the labeled substrate. All the compounds were also tested on 17 alpha-hydroxylase/C17,20-lyase (P450 17), an enzyme of therapeutic interest for the treatment of prostatic diseases. The goal to find new potent inhibitors of aromatase was reached with the xanthone derivatives 22d,e (IC(50) values 43 and 40 nM, respectively), which exceeded the potency of the known reference drug fadrozole and also showed high selectivity with respect to P450 17. Moreover, compounds 22g-i based on the same xanthonic nucleus showed fairly high potency as P450 17 inhibitors (IC(50) values 220, 130, and 42 nM, respectively). Thus, they might be new leads for the development of drug candidates for androgen-dependent diseases.

In vitro evaluation of newly developed chalcone analogues in human cancer cells.

PURPOSE: Among flavonoids, chalcones have been identified as interesting compounds having chemopreventive and antitumor properties. We studied a panel of newly developed chalcone analogues (S1-S10) using MDA-MB 231 and MCF-7 ADRr breast cancer cells and the T-leukemic Jurkat cell line. Quercetin was used as the reference compound. METHODS: Antiproliferative activity was evaluated by cell counts performed after 72 h of exposure to the drugs. DNA analysis and redox activity were evaluated using flow cytometry. Apoptosis was assessed by morphological analysis, using YOYO-1 as DNA dye; p-glycoprotein function was ascertained by quantitating the efflux of rhodamine 123. RESULTS: All cells were sensitive to chalcone analogues yielding IC50 in micromolar concentrations with the following order regardless of the multidrug resistance (MDR) status: S1 > S2 > quercetin. S1 and S2, the most active compounds, were selected to evaluate their effect on the cell cycle, apoptosis, redox activity, and modulation of the p-glycoprotein function. No significant perturbation in cell cycle was seen with concentration up to 1 microM after 24 h. After 72 h a slight increase in G2/M block and DNA fragmentation occurred at 10 microM. Morphological analysis of apoptosis showed that chalcone analogues induced apoptosis to a higher extent than quercetin. Redox analysis demonstrated that all substances were able to increase intracellular thiol levels, which returned to baseline value after 24 h for all drugs except quercetin. Production of reactive oxygen species was essentially unaffected by all compounds. Finally, in MDR-positive MCF-7 ADRr cells chalcone analogues were unable to modulate p-glycoprotein function while quercetin was able to. CONCLUSIONS: Newly developed S1 and S2 chalcones have a different but higher antitumor activity than quercetin and could be considered as potential new anticancer drugs.

Synthesis and biological activity of some rigid analogues of flavone-8-acetic acid.

Some rigid analogues of flavone-8-acetic acid are described. Direct in vitro toxicity of the synthesised compounds was evaluated towards four tumoral cell lines and the ability of these compounds to stimulate mouse peritoneal macrophages in culture to become tumoricidal (indirect toxicity) was also studied. All compounds were able to induce direct cytotoxicity only at very high concentrations but showed a remarkable indirect activity. In particular compound 4d was able to significantly increase macrophage lytic properties and has been selected for further investigations.

SAR of 9-amino-1,2,3,4-tetrahydroacridine-based acetylcholinesterase inhibitors: synthesis, enzyme inhibitory activity, QSAR, and structure-based CoMFA of tacrine analogues.

In this study, we attempted to derive a comprehensive SAR picture for the class of acetylcholinesterase (AChE) inhibitors related to tacrine, a drug currently in use for the treatment of the Alzheimer's disease. To this aim, we synthesized and tested a series of 9-amino-1,2,3,4-tetrahydroacridine derivatives substituted in the positions 6 and 7 of the acridine nucleus and bearing selected groups on the 9-amino function. By means of the Hansch approach, QSAR equations were obtained, quantitatively accounting for both the detrimental steric effect of substituents in position 7 and the favorable electron-attracting effect exerted by substituents in positions 6 and 7 of the 9-amino-1,2,3,4-tetrahydroacridine derivatives. The three-dimensional (3D) properties of the inhibitors were taken into consideration by performing a CoMFA analysis on the series of AChE inhibitors made by 12 9-amino-1,2,3, 4-tetrahydroacridines and 13 11H-indeno[1,2-b]quinolin-10-ylamines previously developed in our laboratory. The alignment of the molecules to be submitted to the CoMFA procedure was carried out by taking advantage of docking models calculated for the interactions of both the unsubstituted 9-amino-1,2,3,4-tetrahydroacridine and 11H-indeno[1,2-b]quinolin-10-ylamine with the target enzyme. A highly significant CoMFA model was obtained using the steric field alone, and the features of such a 3D QSAR model were compared with the classical QSAR equations previously calculated. The two models appeared consistent, the main aspects they had in common being (a) the individuation of the strongly negative contribution of the substituents in position 7 of tacrine and (b) a tentative assignment of the hydrophobic character to the favorable effect exerted by the substituents in position 6. Finally, a new previously unreported tacrine derivative designed on the basis of both the classical and the 3D QSAR equations was synthesized and kinetically evaluated, to test the predictive ability of the QSAR models. The 6-bromo-9-amino-1,2,3,4-tetrahydroacridine was predicted to have a pIC(50) value of 7.31 by the classical QSAR model and 7.40 by the CoMFA model, while its experimental IC(50) value was equal to 0.066 (+/-0.009) microM, corresponding to a pIC(50) of 7.18, showing a reasonable agreement between predicted and observed AChE inhibition data.

Acetylcholinesterase inhibitors for potential use in Alzheimer's disease: molecular modeling, synthesis and kinetic evaluation of 11H-indeno-[1,2-b]-quinolin-10-ylamine derivatives.

Continuing our work on tetracyclic tacrine analogues, we synthesized a series of acetylcholinesterase (AChE) inhibitors of 11H-indeno-[1,2-b]-quinolin-10-ylaminic structure. Selected substituents were placed in synthetically accessible positions of the tetracyclic nucleus, in order to explore the structure-activity relationships (SAR) and the mode of action of this class of anticholinesterases. A molecular modeling investigation of the binding interaction of the lead compound (1a) with the AChE active site was performed, from which it resulted that, despite the rather wide and rigid structure of 1a, there may still be the possibility to introduce some small substituent in some positions of the tetracycle. However, from the examination of the experimental IC50 values, it derived that the indenoquinoline nucleus probably represents the maximum allowable molecular size for rigid compounds binding to AChE. In fact, only a fluorine atom in position 2 maintains the AChE inhibitory potency of the parent compound, and, actually, increases the AChE-selectivity with respect to the butyrylcholinesterase inhibition. By studying the kinetics of AChE inhibition for two representative compounds of the series, it resulted that the lead compound (1a) shows an inhibition of mixed type, binding to both the active and the peripheral sites, while the more sterically hindered analogue 2n seems to interact only at the external binding site of the enzyme. This finding seems particularly important in the context of Alzheimer's disease research in the light of recent observations showing that peripheral AChE inhibitors might decrease the aggregating effects of the enzyme on the beta-amyloid peptide (betaA).

Synthesis of flavone-2'-carboxylic acid analogues as potential antitumor agents.

Some flavone-2'-carboxylic acid analogues are described. Direct in vitro toxicity of the synthesized compounds was evaluated towards four tumoral cell lines, and the ability of these compounds to stimulate mouse peritoneal macrophages in culture to become tumoricidal (indirect toxicity) was also studied. Direct cytotoxic activity was very low for all derivatives. However, almost all compounds showed a remarkable increase of indirect cytotoxicity. In particular, compound 3i, which has an F atom in the 7 position of the flavone ring, was able to increase significantly the macrophage's lytic properties, and has been selected for further investigations.

Synthesis, cytotoxicity and SAR of simple geiparvarin analogues.

Some simple geiparvarin analogues, in which the coumarin moiety has been replaced with an X-substituted benzene ring, are described. The compounds were tested on LoVo cells (human colon carcinoma cell line) and some of them show a cytotoxicity comparable with that of the prototype. A QSAR analysis was also attempted, but it did not provide satisfactory results, mainly because of the limited range of variation of the biological activity.

Some geiparvarin bioisosteres and homologues: synthesis and biological evaluation against human colon carcinoma cells (LoVo).

Some geiparvarin bioisosteres and homologues are described. The compounds were tested on LoVo cells (human colon carcinoma cell line). The EC50 values of the synthesized compounds ranged from 35.04 microM (compound 3) to 11.88 microM (compound 4), while the EC50 value of geiparvarin 1 was 13.30 microM.

Synthesis of a series of Homopterocarpane derivatives with potential antitumor and anti-AIDS activity.

The synthesis of a series of derivatives related to (+/-) cis 6a, 12a-dihydro-6H,7H-[1]-benzopyrano-[4,3-b]-[1]-benzopyran (Homopterocarpane) is described. The synthesized derivatives have been tested at National Cancer Institute in its in vitro anti-cancer and anti-AIDS screening programs. The synthesized compounds are inactive in anti-HIV assay, while some show a GI50 < 100 microM (and < 50 microM in several cell lines) in NCI antitumor screening.