Abstract In this study the effect of pollen source (mesquite and catclaw) on the sensory characteristics (appearance, color, aroma, taste, consistency and visible impurities), and physicochemical properties of raw propolis, and the phenolic content and biological activities of propolis extracts (PEs) was determined. The phenolic composition of PEs was determined by the total phenolic (TPC), flavone and flavonol (FFC), and flavanone and dihydroflavonol content (FDC). The individual phenolic components were analyzed by HPLC-DAD. The antioxidant activity was determined by the ferric-reducing power (FRAP) and free-radical scavenging activity (FRS). The antibacterial activity was evaluated against Gram-positive (Staphylococcus aureus and Listeria innocua) and Gram-negative (Echerichia coli and Salmonella thyphimurium) bacteria. The results showed that sensory characteristic and physicochemical properties of mesquite and catclaw propolis complied with international quality regulations. Fifteen phenolic compounds were identified, of which pinocembrin, naringenin, galangin, chrysin and quercetin were found a high concentration (> 3 mg/g). Mesquite propolis had the highest phenolic content (TFC and FDC), as well as antioxidant activity (> 2.5 mg Fe (II) equivalent/g; > 40% of DPPH radical inhibition) and antibacterial activity against Gram-positive bacterias in the order S. aureus > L. innocua (> 50% of inhibition for both bacterias at 500 µg/mL). These results indicating that pollen source affect the sensory characteristics and physicochemical properties of propolis, as well as the biological activity of their extracts.

Resumen En este estudio se determinó el efecto de la fuente de polen (mezquite y uña de gato) sobre las características sensoriales (apariencia, color, aroma, sabor, consistencia e impurezas visibles) y la propiedades fisicoquímicas del propóleos crudo, así como el contenido fenólico y la actividad biológica de los extractos de propóleos (EP). La composición de fenoles de los EP se determinó por el contenido total de fenoles (CFT), flavonas y flavonoles (CFF), y flavanonas y dihidroflavonoles (CFD). Los componentes fenólicos individuales se analizaron por HPLC-DAD. La actividad antioxidante se determinó por el poder reductor férrico (FRAP) y la inhibición de radicales libres (FRS). La actividad antimicrobiana se evaluó contra bacterias Gram-positivas (Staphylococcus aureus y Listeria innocua) y Gram-negativas (Escherichia coli y Salmonella typhimurium). Los resultados demostraron que las características sensoriales y las propiedades fisicoquímicas del propóleo de mezquite y uña de gato cumplieron con las normas internacionales de calidad. Quince compuestos fenólicos fueron identificados, de los cuales pinocembrina, naringenina, galangina, crisina y quercetina fueron encontrados a mayor concentración (> 3 mg/g). El propóleo de mezquite presentó el mayor contenido fenólico (CFT y CFD), así como actividad antioxidante (> 2.5 mg equivalentes de Fe (II)/g; > 40% de inhibición de radicales DPPH) y antimicrobiana frente a bacterias Gram-positivas en el orden S. aureus > L. innocua (> 50% de inhibición para ambas bacterias a 500 µg/mL). Estos resultados indican que la fuente de polen afecta las características sensoriales y propiedades fisicoquímicas del propóleo, así como la actividad biológica de sus extractos.

O comportamento eletroquímico em função da estrutura de uma série de derivados dos ácidos cafeico e ferúlico, assim como de seus precursores catecol e guaiacol, eletroquimicamente ativos, foi avaliado por voltametria cíclica. Os resultados revelaram que as condições experimentais são a chave para as mudanças no mecanismo de oxidação do guaiacol e ácido ferúlico. A oxidação eletroquímica dos derivados amida do ácido ferúlico revelou que o átomo de nitrogênio desempenha um papel importante na derivatização da superfície do eletrodo. Além disso, a atividade sequestradora de radicais dos compostos, avaliada através da porcentagem de inibição do radical 2,2'-difenil-1-picril-hidrazila, mostrou uma boa correlação com os potenciais de oxidação.

We studied the electrochemical behaviour as a function of the structure of a series of caffeic and ferulic acids derivatives as well as their corresponding redox moieties catechol and guaiacol by cyclic voltammetry. Results revealed that the medium is key for changes in the oxidation mechanism of guaiacol and ferulic acid. Electrochemical oxidation of the ferulic acid amide derivatives revealed that the nitrogen atom plays an important role in the derivatization of the electrode surface. In addition, radical scavenging activity of the compounds evaluated through the percentage of inhibition of the 2,2'-diphenyl-1-picrylhidrazyl radical showed a good relationship with the oxidation potentials.