Investigator: Seann Mulcahy, Providence College

Mentor: Bongsup Cho, University of Rhode Island

Scientific Theme: Molecular Toxicology

Abstract: The proposed research focuses on a class of molecules known as β-carbolines. These molecules are best known for their neurological activity, but they have also shown strong anticancer, antifungal, antibacterial, and antiviral activities. We are particularly interested in the marine metabolite eudistomin U, which has been reported to have antimicrobial and anticancer activity, as well as an ability to bind strongly to DNA. Eudistomin U has a unique structure among β-carbolines, which is characterized by aromatic indole functionality at the 1-position of the β-carboline ring. It is hypothesized that this substitution is important for its biological effects, but a detailed study of the relationship between structure and function is missing. Thus, in order to evaluate its potential as a novel therapeutic agent, the proposed research will study which structural features are necessary for biological activity in detail. First, a short, divergent synthesis of eudistomin U analogs will be developed that will allow for rapid modification at the 1-position of the β-carboline framework with unique aromatic groups. The key step in this sequence is a late-stage Suzuki cross-coupling reaction involving a fully functionalized β-carboline core and a diverse set of boronic acids. The size, electronic nature, substitution pattern, and hydrophobicity of groups at this position will be investigated. Next, the eudistomin U derivatives’ binding to DNA will be characterized through the use of spectroscopic and biophysical techniques. For this, DNA melting, viscosity, and induced ellipticity at increasing ratios of DNA:ligand will establish a preliminary mode of binding. Next, differential scanning calorimetry and surface plasmon resonance will be used to calculate equilibrium binding constants and establish any sequence-specificity. Finally, the cytotoxicity of these synthetic derivatives will also be measured simultaneously in both bacteria and human cancer cells. With these preliminary results, we will be able to understand the relationship between structure and function in this class of molecules, and potentially uncover new drugs with novel mechanisms of action, a goal central to the mission of the NIH.

Human Health Relevance: The development of novel therapies to treat disease is central to improving public health in the 21st century. One route to this goal is to use naturally occurring substances as lead molecules in drug discovery. Eudistomin U is a biologically active metabolite isolated from a marine ascidian that has unique structural features. In order to evaluate its potential as a new drug, we will synthesize several derivatives to determine which structural features are required for its biological effects.