Study of resveratrol-salicylate hybrid analogues: design, synthesis and their biological evaluation as potential multi-target chemopreventive agents

• Author / Creator

  Aldawsari, Fahad Saeed A

• Nature is an important source of bioactive molecules with favorable biological properties. Resveratrol is a natural compound found in grapes and berries and is among other constituents of red wine. This polyphenol has been studied and extensively reported in the literature. Resveratrol exerts a wide range of activities including but are not limited to anti-inflammatory, cardio-protective, antioxidant, chemopreventive and anticancer. It is considered a “multi-target” agent that modulates many cellular signaling pathways. However, its poor pharmacokinetic profile and a track record of contradicting evidence have slowed down (or even precluded) its clinical use. Furthermore, the observed biphasic effects produced by this stilbene in which desirable/undesirable effects are concentration-dependent have raised many questions about its efficacy. Consequently, there are many reports in the scientific literature describing different approaches aimed at improving resveratrol’s pharmacological profile by medicinal chemistry concepts. Acetylsalicylic acid (aspirin) has been used for more than a century and it represents one of the most successful analgesic and anti-inflammatory agents. Despite its notoriously simple chemical formula, aspirin has proven high efficacy not only as an anti-inflammatory agent, but most recently as a potential chemopreventive agent in human cancers, particularly in colon cancer. Resveratrol and aspirin target similar (complementary) enzymes and receptors involved in the inflammation-to-cancer process. Therefore, we hypothesized that the chemical combination of resveratrol with a salicylate moiety would provide a new “hybrid” scaffold combining the biological properties of both parent compounds, and possibly, a novel series of resveratrol-salicylate derivatives with synergistic effects. The design of the new resveratrol-salicylate hybrids was based on the addition of a carboxylic acid (or carboxylate) group at position 3’- in resveratrol’s chemical structure. The biological evaluation (target selection) was based on literature reports describing (a) the role of these targets (COX-2, NF-κB, NO and ROS) in the inflammation-to-cancer process and (b) the effect of the parent resveratrol and/or aspirin. I conducted the synthesis of ten resveratrol-salicylate derivatives by three different chemical reactions, namely the Wittig reaction, the Horner-Wadsworth-Emmons reaction, and the Heck coupling. The Heck coupling produced the desired trans isomer as a major product (55% yield) while the Wittig reaction produced a mixture of both cis and trans isomers. The biological evaluation of the resveratrol-salicylate analogues started with an in vitro enzyme inhibition screening on the CYP1A1 enzyme. We observed a modulatory effect exerted by the test drugs in which some of them were inactive, some produced the desired CYP1A1 inhibition, but others seemed to increase CYP1A1’s enzymatic activity, which was somewhat unexpected. In this regard, compound 3 was the most potent derivative decreasing the activity and the expression (mRNA) of CYP1A1. Using the EROD assay in HT-29 cells, resveratrol at 5µM enhanced TCDD-induced CYP1A activity (unfavorable), showing a clear difference between the hybrid and the parent molecule, resveratrol. In the second study, we evaluated the activity of hybrid drugs to inhibit the catalytic activity of the DNA-methyltransferase (DNMT) enzymes DNMT-1 and DNMT3. Compounds 10 and 9 showed a selective inhibition of the DNMT-3 isoform. In this regard, resveratrol was weaker than the hybrids and it was non-selective. Compounds 3, 4 and 10 showed an in vitro cancer cell proliferation inhibition on three human cancer cells. However, 3 showed a significant cytotoxicity on the non-cancerous MCF 10A which is considered a serious side effect. To support the enzymatic inhibition of CYP1A1 and DNMT by hybrid resveratrol-salicylate molecules, we conducted series of molecular modeling (docking) studies. We observed key binding interactions within the active sites of these two enzymes, correlating the in vitro activity with computer-assisted drug simulations. Finally, we carried out screening assays using compound 10 to evaluate its ability to suppress inflammation both in vitro and in vivo. In these studies, compound 10 exhibited an in vitro inhibition of COX-2 and NF-κB and a significant decrease in ROS production. Furthermore, compound 10 induced cell apoptosis in Jurkat cells. When tested in vivo, compound 10 reduced carrageenan-induced peritonitis and carrageenan-induced paw edema in mice, which were higher than that exerted by resveratrol and its natural analogue, TMS. Compound10 reduced the myeloperoxidase (MPO) activity in the inflamed tissue, particularly at a low dose (10mg/kg). Despite its relatively low stability profile, compound 10 is a promising candidate for future experiments. The favorable activities produced by compound 10 support the overall design of the hybrid resveratrol-salicylate analogues.

• Subjects / Keywords

  • Aspirin
  • Resveratrol
  • Chemoprevention

• Graduation date

  Spring 2016

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3QR4NZ6S

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.