Experimental and Theoretical Investigations of the Chemotherapeutic Drug Capecitabine

Capecitabine (CAP) is a pro-drug of the anti-metabolites group, mainly used in treating breast, gastro-intenstinal and genito-urinary tracts cancers. In spite of the great number of studies reporting about its side-effects, pharmacokinetic and crystal structure investigations, there is a lack of data related to its structure and vibrational properties, as well as an analysis of its behavior at very low concentrations. Considering the complexity and the biological importance of this drug, we considered highly important to obtain a complete structural and vibrational characterization of the title compound. Such investigations could be the starting point for detecting and monitoring the compound in more complex systems like body fluids. Therefore, in this work, we present a joint experimental and theoretical analysis of CAP, using Raman and IR spectroscopic techniques coupled to DFT calculations, aiming to analyze the relative stability of its solid-state tautomers and to explain the vibrational features of the molecule. SERS measurements were also performed on CAP and obtained a very good signal even at low concentrations (0.5·10−4 M). SERS analysis along with the molecular electrostatic potential (MEP) map enabled us to conclude about the adsorption geometry and orientation of the molecules on the gold surface.