Abstract
Bee propolis, especially Euro-Asian poplar propolis, is among the most well-known natural products traditionally used to treat pharyngitis and minor wounds. The aim of this research was to investigate the pharmacological properties responsible for poplar propolis effectiveness using, for the first time, different in vitro approaches applied to a chemically characterized sample. The anti-inflammatory activity was compared with flurbiprofen by determining pro-inflammatory cytokines released by lipopolysaccharide-stimulated human peripheral blood mononuclear cells (PBMC). The antibacterial activity against Gram+ and Gram- bacteria was assessed, as well as antiviral effects on H1N1 influenza a virus. Poplar propolis (5 and 25 µg/mL) exerted a concentration-dependent anti-inflammatory activity. In this range of concentrations, propolis effect was not inferior to flurbiprofen on cytokines released by lipopolysaccharide (LPS)-stimulated human PBMC. Poplar propolis was found to upregulate IL-6 and IL-1β in non-stimulated PBMC. S. aureus, S. pyogenes, and S. pneumoniae were the most susceptible bacterial strains with inhibitory concentrations ranging from 156 to 625 µg/mL. A direct anti-influenza activity was not clearly seen. Effective anti-inflammatory concentrations of propolis were significantly lower than the antibacterial and antiviral ones and results suggested that the anti-inflammatory activity was the most important feature of poplar propolis linked to its rationale use in medicine.
Highlights
Propolis is one of the most precious products produced by bees and mankind has learned to appreciate and use it since immemorial times
Total flavonoids expressed as galangin in PP were 157.48 ± 15.02 mg/g
High concentration of pinocembrin was HPLC analysis showed that the main flavonoid of PP was galangin, at a concentration of
Summary
Propolis is one of the most precious products produced by bees and mankind has learned to appreciate and use it since immemorial times. It is a resinous product made by honeybees: they first collect the resins from gems, buds, and exudates of the plants and mix with bee enzymes, wax, and Biomedicines 2019, 7, 73; doi:10.3390/biomedicines7040073 www.mdpi.com/journal/biomedicines. Flavanones, flavonols, isoflavones, and isoflavans are present in various types of propolis, which differ in quality and abundance of such compounds. Caffeic acid phenethyl ester (CAPE) is another active component present in propolis produced by European, Asian, and American honeybees [4]. Tetracyclic and pentacyclic triterpenes occur [3]
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