Design, Synthesis, and Biological Evaluation of New Type of Gemini Analogues with a Cyclopropane Moiety in Their Side Chain.

We synthesized two new gemini analogues, UG-480 and UG-481, that incorporate a modified longer side chain containing a cyclopropane group. The evaluation of the bioactivities of the two gemini analogues indicated that the 17,20 threo (20S) compound, UG-480, is the most active one and is as active as 1,25(OH)2D3. Docking and molecular dynamics (MD) data showed that the compounds bind efficiently to vitamin D receptor (VDR) with UG-480 to form an energetically more favorable interaction with His397. Structural analysis indicated that whereas the UG-480 compound efficiently stabilizes the active VDR conformation, it induces conformational changes in the H6-H7 VDR region that are greater than those induced by the parental Gemini and that this is due to the occupancy of the secondary channel by its modified side chain.

Synthesis of a novel analog of calcitriol and its biological evaluation as antitumor agent.

Calcitriol analogs have shown promising potential as compounds to be used in cancer chemotherapy. This report presents the synthesis of a novel vitamin D3 derivative with an amide and a carboxyl group in its side chain, called ML-344. In addition, we report its in vitro antitumor activity and its in vivo calcemic effects. We demonstrate that the analog decreases cell viability and retards cell migration of different breast, glioblastoma and head and neck cancer cell lines. Additionally, unlike calcitriol, ML-344 does not display citotoxicity to the murine non-malignant mammary cells and human astrocytes. In concordance with the antimigratory effects found in breast cancer cells, ML-344 decreased the invasive capacity and induced a rearrangement of the actin cytoskeleton in the LM3 breast cancer cell line. In relation to the in vivo studies, the analog did not cause hypercalcemic effects in CF1 mice administered daily at 5 µg/Kg of body weight during a period of 264 h. Finally, computational studies were performed to evaluate the potential binding of the analog to the vitamin D receptor and the in silico assays showed that ML-344 is able to bind to VDR with interesting particularities and greater affinity than calcitriol. Altogether, these results suggest that ML-344 has a promising potential as an antitumor agent with a differential effect between tumor and non-malignant cells.

Synthesis and characterization of supramolecular systems containing nifedipine, ß-cyclodextrin and aspartic acid.

The purpose of this work was to characterize complexes of nifedipine with ß-cyclodextrin (ß-CD), with and without auxiliary agents, to improve aqueous solubility and the dissolution profile of nifedipine. Complexes were characterized using infrared spectroscopy, thermoanalytical methods, powder X-Ray diffraction, scanning electron microscopy, phase solubility analysis and dissolution studies. Spatial configurations were determined by NMR and further examined using computational techniques. This investigation showed that the amino acid Asp was the most efficient auxiliary agent for multicomponent complexes. The spatial configurations were consistent with those obtained by molecular modelling; evidencing that nifedipine inserted its aromatic ring into ß-CD, in all complexes, with Asp interacting with the wide hydrophilic rim of ß-CD. The dissolution rates of nifedipine:ß-CD:Asp complexes were significantly increased compared to those of the pure drug or nifedipine:ß-CD. These results indicate that the nifedipine:ß-CD:Asp system is a promising approach for the preparation of optimized formulations of nifedipine.

Antitumoral effects of the alkynylphosphonate analogue of calcitriol EM1 on glioblastoma multiforme cells.

Glioblastoma multiforme (GBM) is the worst and most common brain tumor, characterized by high proliferation and invasion rates. The current standard treatment is mainly based on chemoradiotherapy and this approach has slightly improved patient survival. Thus, novel strategies aimed at prolonging the survival and ensuring a better quality of life are necessary. In the present work, we investigated the antitumoral effect of the novel analogue of calcitriol EM1 on GBM cells employing in vitro, in silico, and in vivo assays. In vitro, we demonstrated that EM1 treatment selectively decreases the viability of murine and human tumor cells without affecting that of normal human astrocytes. The analysis of the mechanisms showed that EM1 produces cell cycle arrest in the T98G cell line, which is accompanied by an increase in p21, p27, p57 protein levels and a decrease in cyclin D1, p-Akt-S473, p-ERK1/2 and c-Jun expression. Moreover, EM1 treatment also exerts in GBM cells anti-migratory effects and decreases their invasive capacity by a reduction in MMP-9 proteolytic activity. In silico, we demonstrated that EM1 is able to bind to the vitamin D receptor with greater affinity than calcitriol. Finally, we showed that EM1 treatment of nude mice administered at 50ug/kg body weight during 21days neither induces hypercalcemia nor toxicity effects. In conclusion, all the results indicate the potential of EM1 analogue as a promising therapeutic alternative for GBM treatment.

The UVB1 Vitamin D analogue inhibits colorectal carcinoma progression.

Vitamin D has been shown to display a wide variety of antitumour effects, but their therapeutic use is limited by its severe side effects. We have designed and synthesized a Gemini vitamin D analogue of calcitriol (UVB1) which has shown to display antineoplastic effects on different cancer cell lines without causing hypercalcemia. The aim of this work has been to investigate, by employing in silico, in vitro, and in vivo assays, whether UVB1 inhibits human colorectal carcinoma progression. We demonstrated that UVB1 induces apoptotic cell death and retards cellular migration and invasion of HCT116 colorectal carcinoma cells. Moreover, the analogue reduced the tumour volume in vivo, and modulated the expression of Bax, E-cadherin and nuclear ß-catenin in tumour animal tissues without producing toxic effects. In silico analysis showed that UVB1 exhibits greater affinity for the ligand binding domain of vitamin D receptor than calcitriol, and that several characteristics in the three-dimensional conformation of VDR may influence the biological effects. These results demonstrate that the Gemini vitamin D analogue affects the growth of the colorectal cancer and suggest that UVB1 is a potential chemotherapeutic agent for treatment of this disease.

Homodiselenacalix[4]arenes: Molecules with Unique Channelled Crystal Structures.

A synthetic route towards homodiselenacalix[4]arene macrocycles is presented, based on the dynamic covalent chemistry of diselenides. The calixarene inner rim is decorated with either alkoxy or tert-butyl ester groups. Single-crystal X-ray analysis of two THF solvates with methoxy and ethoxy substituents reveals the high similarity of their molecular structures and alterations on the supramolecular level. In both crystal structures, solvent channels are present and differ in both shape and capacity. Furthermore, the methoxy-substituted macrocycle undergoes a single-crystal-to-single-crystal transformation during which the molecular structure changes its conformation from 1,3-alternate (loaded with THF/water) to 1,2-alternate (apohost form). Molecular modelling techniques were applied to explore the conformational and energetic behaviour of the macrocycles.

Increasing doxycycline hyclate photostability by complexation with ß-cyclodextrin.

Doxycycline hyclate (DOX) is a highly photosensitive drug, a feature that limits the stability of the corresponding dosage forms. The main objectives of this work were the preparation and characterization of an inclusion complex of DOX with ß-cyclodextrin (ßCD) and to investigate if this approach could improve the photostability of the drug. Guest-host interactions were investigated using nuclear magnetic resonance, which were afterwards combined with molecular modeling methods to study the complex formation and its three-dimensional structure was proposed. A freeze-drying method was applied to obtain the complex in the solid state, which was further confirmed by thermal and spectroscopic techniques. To evaluate the complexation effect on DOX integrity, the photostability of the inclusion complex was studied, with a significant decrease in the photodegradation of DOX being found in aqueous solution upon complexation. Finally, the photoprotection produced by the complexation was evaluated by means of an antimicrobial assay. Overall, the presented results suggest that the formulation of DOX complexed with ßCD constitutes an interesting approach for the preparation of pharmaceutical dosage forms of DOX with enhanced stability properties.

In vitro and in vivo pharmacokinetic characterization of two novel prodrugs of zidovudine.

This work deals with the in vitro and in vivo pharmacokinetic characterization of 3'-azido-2',3'-dideoxy-5'-O-oxalatoylthymidine (AZT-Ac) and 3'-azido-2',3'-dideoxy-5'-O-isonicotinoyl-thymidine (AZT-Iso), two novel prodrugs of the anti-HIV agent zidovudine [3'-azido-2',3'-dideoxythymidine (AZT)]. AZT, AZT-Ac and AZT-Iso intestinal permeation properties and plasma concentration profiles in rats after intravenous administration were studied. Using the everted gut sac intestinal permeation assay, it was observed that AZT was subjected to saturable transport mechanisms in the jejunum and the proximal ileum, while no saturation was found in the distal ileum. AZT-Ac was able to permeate the intestinal segment at a lower rate than AZT but resisting enzymatic hydrolysis, while no evidence of saturation was found. On the other hand, AZT-Iso was completely hydrolyzed in the intestinal tissue, with AZT being found in the permeated samples. In vivo studies demonstrated that AZT plasma half-life (t(1/2)) is extended after administration of AZT-Ac compared to AZT (2.16 and 0.96h, respectively), while after administering AZT-Iso the t(1/2) of the regenerated AZT was shorter (0.38h). A relationship is proposed between these observed in vivo pharmacokinetic features and previous studies of protein-binding properties, concluding that AZT-Ac is a very promising prodrug of AZT in the search for more effective and safer anti-HIV agents.