Comparison of thermal effects of stilbenoid analogs in lipid bilayers using differential scanning calorimetry and molecular dynamics: correlation of thermal effects and topographical position with antioxidant activity.

In previous studies it was shown that cannabinoids (CBs) bearing a phenolic hydroxyl group modify the thermal properties of lipid bilayers more significantly than methylated congeners. These distinct differential properties were attributed to the fact that phenolic hydroxyl groups constitute an anchoring group in the vicinity of the head-group, while the methylated analogs are embedded deeper towards the hydrophobic region of the lipid bilayers. In this work the thermal effects of synthetic polyphenolic stilbenoid analogs and their methylated congeners have been studied using differential scanning calorimetry (DSC). Molecular dynamics (MD) simulations have been performed to explain the DSC results. Thus, two of their phenolic hydroxyl groups orient in the lipid bilayers in such a way that they anchor in the region of the head-group. In contrast, their methoxy congeners cannot anchor effectively and are embedded deeper in the hydrophobic segment of the lipid bilayers. The MD results explain the fact that hydroxystilbenoid analogs exert more significant effects on the pretransition than their methoxy congeners, especially at low concentrations. To maximize the polar interactions, the two phenolic hydroxyl groups are localized in the vicinity of the head-group region, directing the remaining hydroxy group in the hydrophobic region. This topographical position of stilbenoid analogs forms a mismatch that explains the significant broadening of the width of the phase transition and lowering of the main phase-transition temperature in the lipid bilayers. At high concentrations, hydroxy and nonhydroxy analogs appear to form different domains. The correlation of thermal effects with antioxidant activity is discussed.

New hydroxystilbenoid derivatives endowed with neuroprotective activity and devoid of interference with estrogen and aryl hydrocarbon receptor-mediated transcription.

We have synthesized a series of new (E) stilbenoid derivatives containing hydroxy groups at ring positions identical or similar to those of trans-resveratrol and bearing one or two bulky electron donating groups ortho to 4'-OH and we have evaluated their neuroprotective activity using glutamate-challenged HT22 hippocampal neurons to model oxidative stress-induced neuronal cell death. The most active derivatives, 5-{(E)-2-[3,5-bis(1-ethylpropyl)-4-hydroxyphenyl]ethenyl}-1,3-benzenediol (2), 5-[(E)-2-(3,5-di-tert-butyl-4-hydroxyphenylethenyl)]-1,3-benzenediol (4) and 5-{(1E,3E)-4-[3,5-bis(1-ethylpropyl)-4-hydroxyphenyl]-1,3-butadienyl}-1,3-benzenediol (6), had EC(50) values of 30, 45 and 12nM, respectively, and were ca. 100 to 400-fold more potent than resveratrol. Derivatives 2, 4 and 6 lacked cytotoxic activity against HT22 cells and estrogen receptor agonist or antagonist activity in estrogen response element-dependent gene expression and in estrogen-dependent proliferation of MCF-7 human breast cancer cells. In addition, they were incapable of interfering with aryl hydrocarbon receptor-mediated xenobiotic response element-dependent gene expression. Derivatives 2, 4 and 6 might assist in the development of lead candidates against oxidative stress-driven neurodegenerative diseases that will not increase endocrine cancer risk nor affect drug activation and detoxification mechanisms.

Synthetic and computational studies on the tricarboxylate core of 6,7-dideoxysqualestatin H5 involving a carbonyl ylide cycloaddition-rearrangement.

Reaction of diazodiketoesters 17 and 28 with methyl glyoxylate in the presence of catalytic rhodium(II) acetate generates predominantly the 6,8-dioxabicyclo[3.2.1]octanes 29 and 30, respectively. Acid-catalysed rearrangement of the corresponding alcohol 31 favours, at equilibrium, the 2,8-dioxabicyclo[3.2.1]octane skeleton 33 of the squalestatins-zaragozic acids. Force field calculations on the position of the equilibrium gave misleading results. DFT calculations were correct in suggesting that the energy difference between 31 and 33 should be small, but did not always suggest the right major product. Calculation of the NMR spectra of the similar structures could be used to assign the isomers with a high level of confidence.

Dendrimers as biopharmaceuticals: synthesis and properties.

Two general aspects which need to be considered for the successful application of dendrimers for biomedical purposes are their availability at an acceptable cost and their suitability as regards their pharmacodynamic and pharmacokinetic properties. These two aspects are covered in this review. In the first part, synthetic strategies for the preparation of dendrimers are outlined and emphasis is given to recent work on methodologies whose aim is the development of more efficient routes to dendrimers in terms of the materials used for their synthesis as well as in terms of the procedures required for their purification. These include procedures involving double-stage and double exponential synthesis, orthogonal coupling strategies, self-assembly and solid-phase approaches, as well as particularly useful synthetic protocols such as those used in "click chemistry". The second part of the review deals with the way in which the size, chemical constitution and physicochemical properties of dendrimers used for drug delivery may affect pharmacodynamic and pharmacokinetic parameters which are important considerations for drug bioavailability. This is illustrated by an overview of examples from recent work involving non-steroidal anti-inflammatory drugs, anticancer drugs and antibacterials.

Engineered chimeric enzymes as tools for drug discovery: generating reliable bacterial screens for the detection, discovery, and assessment of estrogen receptor modulators.

Engineered protein-based sensors of ligand binding have emerged as attractive tools for the discovery of therapeutic compounds through simple screening systems. We have previously shown that engineered chimeric enzymes, which combine the ligand-binding domains of nuclear hormone receptors with a highly sensitive thymidylate synthase reporter, yield simple sensors that report the presence of hormone-like compounds through changes in bacterial growth. This work describes an optimized estrogen sensor in Escherichia coli with extraordinary reliability in identifying diverse estrogenic compounds and in differentiating between their agonistic/antagonistic pharmacological effects. The ability of this system to assist the discovery of new estrogen-mimicking compounds was validated by screening a small compound library, which led to the identification of two structurally novel estrogen receptor modulators and the accurate prediction of their agonistic/antagonistic biocharacter in human cells. Strong evidence is presented here that the ability of our sensor to detect ligand binding and recognize pharmacologically critical properties arises from allosteric communication between the artificially combined protein domains, where different ligand-induced conformational changes in the receptor are transmitted to the catalytic domain and translated to distinct levels of enzymic efficiency. To the best of our knowledge, this is one of the first examples of an engineered enzyme with the ability to sense multiple receptor conformations and to be either activated or inactivated depending on the nature of the bound effector molecule. Because the proposed mechanism of ligand dependence is not specific to nuclear hormone receptors, we anticipate that our protein engineering strategy will be applicable to the construction of simple sensors for different classes of (therapeutic) binding proteins.