Antimicrobial and antioxidant activities of a Portuguese honey harvested over two consecutive years

Abstract

Honey, a natural mixture produced by honeybees from the nectar collected from flowers and other parts of plants and mixed with substances resulting from bee’s metabolism[1], is mainly composed by carbohydrates, particularly fructose and glucose, other sugars, water, and also other bioactive substances including flavonoids and phenols[2]. These compounds have been associated with diverse bioactivities such as antibacterial, antifungal and antioxidant activities, among others[2]. The aim of this work is related with the investigation on two Portuguese honey samples, collected in 2017 and 2018, from an apiary located in a National Park in the North of Portugal, a protected area from Gerês region, particularly regarding its antimicrobial activity, antioxidant potential and chemical composition. Total phenolic and ortho-diphenol contents were determined for the aqueous extracts of honey obtained from both samples. Antimicrobial activity of the honey extracts was evaluated by the agar dilution method in a panel of seven bacterial and two yeast species, the results being expressed as minimum inhibitory concentration (MIC). DPPH• scavenging assay was performed to evaluate the in vitro antioxidant capacity of the same honey extracts. Both Portuguese honey samples showed antimicrobial activity and antioxidant potential, with the sample from 2018 exhibiting stronger antifungal activity and higher ability to scavenge DPPH free radicals. For this sample, ortho-diphenol compounds were present in higher amounts, being strongly correlated with the bioactivities studied in this work. These results exalt the potentialities of these Portuguese honey samples to be used for several applications, specifically in health[1,3].