Propolis from New Zealand and international sources: analysis and comparison of antioxidant and polyphenolic profiles

Abstract

Propolis is a sticky residue derived from the resin of tree bud exudates, consisting of waxes, essential oils, pollen, inorganic substances and polyphenolic constituents. As well as providing protection for plants against micro-organisms and UV damage, propolis is associated with various bioactivities such as anti-inflammatory, anti-tumour and antioxidant properties. Due to these beneficial properties, propolis is used as an active ingredient in dietary supplements to treat various health conditions. Factors such as plant source and geographic origin influence the polyphenolic profiles and bioactivities of these different types of propolis. The aim of this project was to characterise the chemical constituents and associated bioactivities of propolis, and determine its potential as a health-promoting agent. In order to characterise New Zealand propolis, total phenolic and flavonoid contents, polyphenolic profiles and antioxidant activities of 46 New Zealand propolis samples were examined and compared with overseas propolis samples from Germany, Argentina and Uruguay, and commercially available propolis samples. In general, New Zealand propolis samples contained higher phenolic and flavonoid contents as well as higher levels of antioxidant activities compared to overseas propolis samples. New Zealand and overseas propolis samples all contained high levels of pinocembrin, pinobanksin acetate, galangin and chrysin, but New Zealand propolis samples contained higher concentrations of galangin. Rutin, a phenolic compound, was only detected in some New Zealand propolis samples. Commercial propolis samples showed a wide variability in their phenolic and flavonoid contents and antioxidant activities. However, the polyphenolic profiles of brown commercial propolis samples were similar with the polyphenolic profiles of New Zealand and overseas samples, with high concentrations of pinocembrin, galangin, chrysin and cinnamic acid. This similarity indicated that the brown propolis samples examined in this study share similar plant sources, most likely from the Populus genus. This study demonstrated that New Zealand propolis may be a good source of polyphenolic compounds with high level of antioxidant activities, suggesting its potential for health-promoting benefits.