Comparative study between Chinese propolis and Brazilian green propolis: metabolite profile and bioactivity
Propolis, a gift of nature produced by bees, is a resinous mixture of products from plants and bee’s secretions. Among different types, Chinese propolis (ChPs) and Brazilian green propolis (BrGPs) have been shown to contain excellent medicinal properties by virtue of their high content of phenolic acids and flavonoids. Despite extensive research in the field, reports comparing propolis from different geographical areas are still seldom, compromising our current understanding of the potential therapeutic effect associated to propolis and its derived compounds. In the present study, the content of ethanol extract, total flavonoids and total phenolic acids of 12 batches of ChPs and 12 batches of BrGPs were quantified. Then, UPLC-ESI-qTOF-MS metabolic profiling and pattern recognition of all samples were carried to unambiguously identify novel phenolics present in propolis, followed by comparative quantification in Chinese and Brazilian samples by HPLC. Additionally, the anti-oxidant activity of propolis against DPPH free radicals and hydroxyl free radicals generated by Fenton reaction were evaluated. Finally, experiments using an in vivo model for LPS-induced inflammation on C57BL/6J mice confirmed the anti-inflammatory activity of ChPs and BrGPs. Both groups of propolis inhibited LPS-induced hepatic IL-1β, IL-6 and TNF-α expression and down regulated the levels of these pro-inflammatory cytokines in serum. Interestingly, even when ChPs and BrGPs show similar anti-inflammatory potential, our results show that they contain very different levels of ethanol extract, total flavonoids and total phenolic acids and in fact, LC-MS metabolic profiling and pattern recognition can effectively distinguish ChPs and BrGPs. Moreover, all the propolis tested showed good anti-oxidant activity and no significant difference of free radical scavenging capacity existed between ChPs and BrGPs. In conclusion, ChPs and BrGPs have a distinct chemome, but their antioxidant and anti-inflammatory activities are similar. Results generated in this study provide proof of concept that propolis from different geographical locations can be used as a novel source of new anti-inflammatory drugs.