Piero Valenti

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 μM after 24 h. After 72 h a slight increase in G2/M block and DNA fragmentation occurred at 10 μM. 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.

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 Alzheimers 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 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.

Acetylcholinesterase inhibitors as a starting point towards improved Alzheimer's disease therapeutics.

The knowledge about the pathogenesis and the development of the neurodegeneration associated with Alzheimers disease (AD) has been organised throughout the years into two theories, namely the cholinergic and the amyloid hypotheses. The loss of cholinergic neurotransmission and the abnormal aggregation and deposition of the amyloid-beta peptide (A beta) in the brain are retained as the central events by the two theories, respectively. These phenomena and their pathological consequences are the main targets of the drug discovery strategies based on each hypothesis. However, the two paradigms share some common aspects as shown by several experimental evidences, such that they might even fit into a unifying scenario of neuropathology and neurodegeneration. In this context, in a perspective of drug discovery, the enzyme acetylcholinesterase (AChE) holds a key position, as it is a main target for cholinomimetic AD drugs being responsible for the breakdown of the neurotransmitter, and it is also involved in the aggregation of A beta and the formation of the neurotoxic fibrils. Following this view, in recent years, a drug design strategy has emerged, directed to finding molecules able to inhibit both of these actions exerted by AChE. In this review, we will briefly introduce the biological basis of this strategy, and then will account for the early results obtained in this field in our and in other laboratories. The main focus will be on potential lead compounds for which some experimental evidence exists supporting the hypothesis of their dual action, as AChE inhibitors and blockers of the AChE-induced A beta aggregation.

Design, synthesis, and evaluation of benzophenone derivatives as novel acetylcholinesterase inhibitors

Starting from a structure-based drug design, new acetylcholinesterase inhibitors were designed and synthesized as analogues of donepezil. The compounds were composed by an aromatic function and a tertiary amino moiety connected by a suitable spacer. In particular, the benzophenone nucleus and the N,N-benzylmethylamine function were selected. The easily accessible three-step synthesis of these compounds resulted to be significantly less difficult and expensive than that of donepezil. Several compounds possess anti-cholinesterase activity in the order of micro and sub-micromolar. Particularly, compounds 1 and 10 were the most potent inhibitors of the series.

Chemiluminescence imaging in bioanalysis

The development, analytical performance and applications of chemiluminescence imaging as a tool for quantitative analyte localization in target biological specimens are described. The detection of acetylcholinesterase activity both in array format and on a target surface are described. A proposed application of the method is a 384 well microtiter format assay for high throughput screening of acetylcholinesterase inhibitors such as tacrine, a drug widely used in the treatment of Alzheimers disease, and two recently developed analogues. The chemiluminescent system in conjunction with optical microscopy allowed localization of acetylcholinesterase in brain tissue sections. We also describe the chemiluminescent immunohistochemical localization of interleukin 8 in Helicobacter pylori infected gastric mucosa cryosections and an in situ hybridization assay for the detection of herpes simplex virus DNA in single cells.

Cardiovascular hybrid drugs: new benzazepinone derivatives as bradycardic agents endowed with selective β1-Non-competitive antagonism

The synthesis and pharmacological profile of some hybrid compounds bearing both the benzazepinone moiety present in Zatebradine and typical beta-blocker aryloxypropanolamine groups are described. The new compounds proved to be endowed with negative chronotropic and inotropic activity and are weak vasorelaxant agents. The cardiodepressant action is probably due to selective beta(1)-noncompetitive reversible antagonism. Both enantiomers of the most active compound 5c were synthesized and they showed a different cardiovascular profile, that is (+)-(R)-enantiomer displays affinity for cardiac beta(1)-adrenoceptors, while (-)-(S)-enantiomer shows specificity for vessel smooth muscle.

Acetylcholinesterase inhibition by tacrine analogues

Abstract Analogues of tacrine were synthesized and evaluated for acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory activity. Compound 2a was the most potent inhibitor of AChE with a higher selectivity than tacrine for AChE over BuChE. Tacrine, on the other hand, showed the opposite behaviour with a weaker inhibitory effect on AChE than on BuChe. The compounds displayed correlated activities in isolated enzymes as well as in rat brain homogenates.

Flavone and xanthone derivatives related to fluoroquinolones

A number of flavone and xanthone derivatives bearing some characteristic features of fluoroquinolones such as the fluorine atom and an ortho piperazine ring are described. The new compounds have been tested for possible cytotoxic and antimicrobial activities. Cytotoxicity of both groups of compounds is rather poor, while the antibacterial activity is restricted to xanthones.

RM values of xanthone derivatives in structure-activity studies

Abstract The RM values of a series of xanthone derivaties obtained in a chromatographic system were correlated with the calculated log P values. The relationship between lipophilic character and acute toxicity in mice was also studied. The equations describing the structure-activity relationship indicate the importance of lipophilic character in determining the acute toxicity of xanthone derivatives in mice.