Constituents of Hondurian Propolis with Inhibitory Effects on Saccharomyces cerevisiae Multidrug Resistance Protein Pdr5p

Chemical investigation of a propolis sample collected in Honduras has led to the isolation of the new (E,Z)-cinnamyl cinnamate (2) together with 14 known compounds: 6 cinnamic ester derivatives, 2 flavanones, 1 chalcone, 2 triterpenes, and 3 aromatic acids. Structural determination was accomplished by spectroscopic analysis, particularly two-dimensional (2D) nuclear magnetic resonance (NMR) and electrospray ionization–tandem mass spectrometry (ESI–MS/MS) techniques. Futhermore, we checked the ability of the propolis extract and the most representative compounds of each class (1, 5, 8, and 10) to inhibit the activity of Pdr5p, a protein responsible for a multidrug resistance phenotype in yeast. The present study appears to be the first report on Honduras propolis. Isolated cinnamic ester derivatives indicated the possible relation between Honduras propolis and the genus Liquidambar.