Propolis has been proposed as a polyphenolic-rich natural product potentially able to be used for human consumption or even for medicinal proposes. To guarantee a minimum phenolic and flavonoid content and as consequence of their related-biological activities, international requirements of propolis quality are commonly applied. In this work we assessed phenolic and flavonoid contents of propolis; the antioxidant capacity (toward peroxyl radicals and hypochlorous acid); the ability to generate nitric oxide (NO); and, finally the antimicrobial activity of 6 propolis samples from the VI region of Chile. Our results show that the total phenolic and flavonoid content of propolis samples are not always in agreement with their polyphenolic-associated in vitro activities. For example, P03 and P06 samples showed the lowest (25 ± 4 GAE/g propolis) and the highest (105 ± 3 GAE/g propolis) total phenolic content, respectively. This was in agreement with flavonoid content and their Oxygen Radical Absorbance Capacity (ORAC) activity. However, this dependence was not observed toward HOCl, NO release and antimicrobial activity. Based on our results, we consider that, in order to guarantee the antioxidant or antimicrobial in vitro effects, the international regulations of propolis quality should contemplate the convenience of incorporating other simple analytical test such as ORAC or antimicrobial tests.

R. Bridi, G. Nuñez-Quijada, P. Aguilar, P. Martínez, E. Lissi, A. Giordano, and G. Montenegro. 2017. Differences between phenol content and antioxidant capacity of quillay Chilean honeys and their phenolic extracts. Cien. Inv. Agr. 44(3): 252-261. The differences between entire quillay honeys and their separated phenolic extracts in terms of phenolic content, flavonoid content and scavenging activity assessed through an Oxygen Radicals Absorbance Capacity (ORAC) assay were determined. The separated phenolic extracts of honey were obtained using Amberlite XAD-2, which is the procedure most used in analytical methods, biological assays and functional food development. The results showed that phenolic and flavonoid contents and antioxidant activity were higher in entire honeys than in their separated phenolic extracts. The recovery of phenolic acids and flavonoids was variable and depended upon the method employed. The application of polyvinylpolypyrrolidone (PVPP), a water insoluble synthetic polymer, in the separated extracts indicated an important influence of non-phenolic reducing compounds in the polyphenolic content measured by the FolinCiocalteu method. This showed the elution with methanol of these compounds together with phenolic compounds using an Amberlite XAD-2 column. The antioxidant capacity assessed through ORAC-FL and ORAC-PGR was less influenced by the interference of non-phenolic compounds than by that of total phenolic and flavonoid contents.

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