Do Portuguese propolis extracts have effects on DNA damage?

Abstract

Propolis is a natural resinous product produced by bees from tree buds and exudates that is used in the beehives as structural material. Among the various propolis biologically active compounds, flavonoids are some of the most important ones. Flavonoids have been valued by their antigenotoxic effect, which is a direct consequence of their antioxidant properties, as they are reactive oxygen species (ROS) scavengers. ROS are small molecules/free radicals whose effect is associated with various diseases. Extracts rich in flavonoids have been widely used in the food, drug and cosmetic industries.

Propolis has already been intensively studied worldwide, due to its biological properties and potential. However, studies with Portuguese propolis are relatively scarce. The aim of this study is to elucidate the influence of ethanol extracts (EE) of propolis collected between 2010 and 2014 in a Portuguese apiary - Pereiro (P.EEs) - at Beira Alta (district of Guarda), on DNA damage and recovery. Chemical analysis by HPLC shows only minor qualitative differences in the compounds that make up extracts (phenolic acids, flavonoids and derivatives) from propolis samples harvested every year from 2010 to 2014. However, different cytotoxicity is revealed in Saccharomyces cerevisiae cells depending on the respective year or mixture of extracts from different years. All the tested extracts and mixtures show antioxidant effects assessed by the DPPH radical scavenging activity and the reducing power assays, which correlates with their DNA-preventive activity against Fe2+-induced damage, assessed by the DNA topology assay. However, analysis by flow cytometry showed that yeast cells treated with P10.EE appear to be affected when it comes to cell cycle progression, which is in accordance with the high cytotoxicity shown by this extract. In conclusion, the extracts show cytotoxic activity, while their role in oxidative stress is still nuclear.