Comparative study of different Portuguese samples of propolis: pollinic, sensorial, physicochemical, microbiological characterization and antibacterial activity.

The aim of this work was to study four propolis samples from Trás-os-Montes region of Portugal. The propolis samples' color was different, which pollen analysis showed to be due to different botanical sources: Populus sp., Pinus sp., Quercus sp. and Castanea sativa. The data from physicochemical analysis (moisture, soluble and insoluble solids content, pH, conductivity, ash content, wax, total phenolics and flavonoids content) was treated using multivariate statistical tools as cluster heat map, principal components analysis and linear discriminant analysis with the purpose of classifying the sample accordingly to the botanical/geographical origin. The discriminant analysis was applied with stepwise to select the variables that most contribute to sample identification accordingly to pollinic profile. The cross-validation technique was applied, using the leave-one-out procedure, which showed good prediction capabilities of the samples. Microbiologically, the commercial quality was satisfactory, since the samples didn't contain deterioration or pathogenic microorganisms. All the samples studied presented antimicrobial activity against Methicillin-resistant Staphylococcus aureus, in a dose dependent way. The antimicrobial activity was strictly related to the physicochemical composition. This work will allow connecting a particular chemical propolis type to a specific type of biological activity, what is essential for the use in therapeutic applications.