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Santos R.C.,University of Coimbra | Salvador J.A.R.,University of Coimbra | Marin S.,IBUB | Cascante M.,IBUB | And 2 more authors.
Bioorganic and Medicinal Chemistry | Year: 2010

Chemical transformation studies were conducted on betulin and betulinic acid, common plant-derived lupane-type triterpenes. The concise synthesis, via a stepwise approach, of betulin and betulinic acid carbamate and N-acylheterocyclic containing derivatives is described. All new compounds, as well as betulinic acid were tested in vitro for their cytotoxic activity. Most of the compounds have shown a better cytotoxic profile than betulinic acid, including the synthesized betulin derivatives. Compounds 25 and 32 were the most promising derivatives, being up to 12-fold more potent than betulinic acid against human PC-3 cell lines (IC50 values of 1.1 and 1.8 μM, respectively). © 2010 Elsevier Ltd. All rights reserved.

Barragan F.,IBUB | Barragan F.,University of Barcelona | Lopez-Senin P.,IBUB | Salassa L.,University of Warwick | And 5 more authors.
Journal of the American Chemical Society | Year: 2011

A photoactivated ruthenium(II) arene complex has been conjugated to two receptor-binding peptides, a dicarba analogue of octreotide and the Arg-Gly-Asp (RGD) tripeptide. These peptides can act as "tumor-targeting devices" since their receptors are overexpressed on the membranes of tumor cells. Both ruthenium-peptide conjugates are stable in aqueous solution in the dark, but upon irradiation with visible light, the pyridyl-derivatized peptides were selectively photodissociated from the ruthenium complex, as inferred by UV-vis and NMR spectroscopy. Importantly, the reactive aqua species generated from the conjugates, [(η 6-p-cym)Ru(bpm)(H 2O)] 2+, reacted with the model DNA nucleobase 9-ethylguanine as well as with guanines of two DNA sequences, 5′dCATGGCT and 5′dAGCCATG. Interestingly, when irradiation was performed in the presence of the oligonucleotides, a new ruthenium adduct involving both guanines was formed as a consequence of the photodriven loss of p-cymene from the two monofunctional adducts. The release of the arene ligand and the formation of a ruthenated product with a multidentate binding mode might have important implications for the biological activity of such photoactivated ruthenium(II) arene complexes. Finally, photoreactions with the peptide-oligonucleotide hybrid, Phac-His-Gly-Met-linker-p 5′dCATGGCT, also led to arene release and to guanine adducts, including a GG chelate. The lack of interaction with the peptide fragment confirms the preference of such organometallic ruthenium(II) complexes for guanine over other potential biological ligands, such as histidine or methionine amino acids. © 2011 American Chemical Society.

Barragan F.,IBUB | Barragan F.,University of Barcelona | Carrion-Salip D.,University of Girona | Gomez-Pinto I.,CSIC - Institute of Physical Chemistry "Rocasolano" | And 8 more authors.
Bioconjugate Chemistry | Year: 2012

Conjugates of a dicarba analogue of octreotide, a potent somatostatin agonist whose receptors are overexpressed on tumor cells, with [PtCl 2(dap)] (dap = 1-(carboxylic acid)-1,2-diaminoethane) (3), [(η6-bip)Os(4-CO2-pico)Cl] (bip = biphenyl, pico = picolinate) (4), [(η6-p-cym)RuCl(dap)]+ (p-cym = p-cymene) (5), and [(η6-p-cym)RuCl(imidazole-CO 2H)(PPh3)]+ (6), were synthesized by using a solid-phase approach. Conjugates 3-5 readily underwent hydrolysis and DNA binding, whereas conjugate 6 was inert to ligand substitution. NMR spectroscopy and molecular dynamics calculations showed that conjugate formation does not perturb the overall peptide structure. Only 6 exhibited antiproliferative activity in human tumor cells (IC50 = 63 ± 2 μ in MCF-7 cells and IC50 = 26 ± 3 μ in DU-145 cells) with active participation of somatostatin receptors in cellular uptake. Similar cytotoxic activity was found in a normal cell line (IC50 = 45 ± 2.6 μ in CHO cells), which can be attributed to a similar level of expression of somatostatin subtype-2 receptor. These studies provide new insights into the effect of receptor-binding peptide conjugation on the activity of metal-based anticancer drugs, and demonstrate the potential of such hybrid compounds to target tumor cells specifically. © 2012 American Chemical Society.

News Article | December 2, 2016
Site: phys.org

Since it is based on a different principle, this method complements conventional tools and allows going forward in the path of rational drug design. ICREA researcher Xavier Barril, from the Faculty of Pharmacy and Food Sciences and The Institute of Biomedicine of the University of Barcelona (IBUB), has led this project, which has the participation of professor Francesc Xavier Luque and PhD student Sergio Ruiz Carmona, members of the same Faculty. The improvement on efficiency and effectiveness in the discovery of drugs is a key target in pharmaceutical research. In this process, the target are molecules that can be added to a target protein and modify its behavior according to clinical needs. "All current methods to predict if a molecule will join the wished protein are based on affinity, that is, in the complex's thermodynamic stability. What we are proving is that molecules have to create complexes that are structurally stable, and that it is possible to distinguish between active and inactive by looking at what specific interactions are hard to break", says Professor Xavier Barril. This approach has been applied in software that identifies molecules with more possibilities to join the targeted protein. "The method allows selecting molecules that can be starting points to create new drugs", says Barril. "Moreover, -he continues- the process is complementary with existing methods and allows multiplying five times the efficiency of the current processes with lower computational prices. We are actually using it successfully in several projects in the field of cancer and infectious diseases, among others". A new vision for the protein-ligand drugs This work introduces a new way of thinking regarding the ligand-protein interaction. "We don't look at the balancing situation, where two molecules make the best possible interactions, but we also think how the complex will break, which the breaking points are and how we can improve the drug to make it more resistant to separation. Now we have to focus on this phenomenon to understand it better and see if by creating more complex models we can still improve our predictions", says the researcher. The team of the University of Barcelona is already using this method, which is open to all the scientific community. Explore further: New therapeutic target for diseases caused by lack of oxygen More information: Sergio Ruiz-Carmona et al. Dynamic undocking and the quasi-bound state as tools for drug discovery, Nature Chemistry (2016). DOI: 10.1038/nchem.2660

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