Semisynthesis, Characterization and Evaluation of New Adenosine Derivatives as Antiproliferative Agents

C2-linked alkynyl poly-ethylene glycol(PEG) adenosine conjugates as water-soluble adenosine receptor agonists

A series of 12 novel polyethylene-glycol(PEG)-alkynyl C2-adenosine(ADN) conjugates were synthesized using a robust Sonogashira coupling protocol and characterized by NMR spectroscopy and mass spectrometry analysis. The ADN-PEG conjugates showed null to moderate toxicity in murine macrophages and 12c was active against Mycobacterium aurum growth (MIC = 62.5 mg/L). The conjugates were not active against Mycobacterium bovis BCG. Conjugates 10b and 11b exhibited high water solubility with solubility values of 1.22 and 1.18 mg/ml, respectively, in phosphate buffer solutions at pH 6.8. Further, 10b and 11b induced a significant increase in cAMP accumulation in RAW264.7 cells comparable with that induced by adenosine. Analogues 10c, 11c and 12c were docked to the A₁ , A_2A , A_2B and A₃ adenosine receptors (ARs) using crystal-structures and homology models. ADN-PEG-conjugates bearing chains with up to five ethyleneoxy units could be well accommodated within the binding sites of A₁ , A_2A and A₃ ARs. Docking studies showed that compound 10b and 11b were the best A_2A receptor binders of the series, whereas 12c was the best binder for A₁ AR. In summary, introduction of hydrophilic PEG substituents at the C2 of adenine ring significantly improved water solubility and did not affect AR binding properties of the ADN-PEG conjugates.

Two New Adenosine Derivatives and their Antiproliferative Properties, an In Vitro Evaluation

BACKGROUND

Adenosine is a natural nucleoside present in various organs and tissues, where it acts as a modulator of diverse physiological and pathophysiological processes. These actions are mediated by at least four G protein-coupled receptors, which are widely and differentially expressed in tissues. Interestingly, high concentrations of adenosine have been reported in a variety of tumors. In this context, the final output of adenosine in tumorigenesis will likely depend on the constellation of adenosine receptors expressed by tumor and stromal cells. Notably, activation of the A3 receptor can reduce the proliferative capacity of various cancer cells.

OBJECTIVE

The objective of this study is to describe the anti-proliferative effects of two previously synthesized adenosine derivatives with A3 agonist action (compounds 2b and 2f) through in vitro assays.

METHOD

We used gastric and breast cancer cell lines expressing the A3 receptor as in vitro models and theoretical experiments such as molecular dynamics and determination of ADME properties.

RESULTS

The antiproliferative effects of adenosine derivatives (after determining IC50 values) were comparable or even higher than those described for IB-MECA, a commercially available A3 agonist. Among possible mechanisms involved, apoptosis was found to be induced in MCF-7 cells but not in AGS or MDA-MB-231 cells. Surprisingly, we were unable to observe cellular senescence induction upon treatment with compounds 2b and 2f in any of the cell lines studied, although we cannot rule out other forms of cell cycle exit at this point.

CONCLUSION

Both adenosine derivatives showed antiproliferative effects on gastric and breast cancer cell lines, and were able to induce apoptosis, at least in the MCF-7 cell line. Further studies will be necessary to unveil receptor specificity and mechanisms accounting for the antiproliferative properties of these novel semi-synthetic compounds.

Adenosine Derivates as Antioxidant Agents: Synthesis, Characterization, in Vitro Activity, and Theoretical Insights

In this work, we present results about the synthesis and the antioxidant properties of seven adenosine derivatives. Four of these compounds were synthesized by substituting the N6-position of adenosine with aliphatic amines, and three were obtained by modification of the ribose ring. All compounds were obtained in pure form using column chromatography, and their structures were elucidated by infrared spectroscopy (IR) and Nuclear Magnetic Resonance (NMR). All adenosine derivatives were further evaluated in vitro as free radical scavengers. Our results show that compounds 1c, 3, and 5 display a potent antioxidant effect compared with the reference compound ascorbic acid. In addition, the absorption, distribution, metabolism and excretion (ADME) calculations show favorable pharmacokinetic parameters for the set of compounds analyzed, which guarantees their suitability as potential antioxidant drugs. Furthermore, theoretical analyses using Molecular Quantum Similarity and reactivity indices were performed in order to discriminate the different reactive sites involved in oxidative processes.