3-Acyl dihydroflavonols from poplar resins collected by honey bees are active against the bee pathogens Paenibacillus larvae and Ascosphaera apis. (June 2017)

• Record Type: Journal Article
• Authors: Wilson, Michael B.; Pawlus, Alison D.; Brinkman, Doug; Gardner, Gary; Hegeman, Adrian D.; Spivak, Marla; Cohen, Jerry D.
• Is Part Of: Phytochemistry. Volume 138(2017)
• Page Start: 83
• Page End: 92
• Publication Date: 2017-06
• Subjects: Populus -- Salicaceae -- Honey bees (Apis mellifera) -- Paenibacillus larvae -- Ascospharea apis -- Plant resins -- Antimicrobial activity -- Dihydroflavonol -- Propolis; Botanical chemistry -- Periodicals; Biochemistry -- Periodicals; Botany -- Periodicals; Chimie végétale -- Périodiques; 572.2
• DOI: 10.1016/j.phytochem.2017.02.020
• Languages: English
• ISSNs: 0031-9422

Abstract

Abstract: Honey bees, Apis mellifera, collect antimicrobial plant resins from the environment and deposit them in their nests as propolis. This behavior is of practical concern to beekeepers since the presence of propolis in the hive has a variety of benefits, including the suppression of disease symptoms. To connect the benefits that bees derive from propolis with particular resinous plants, we determined the identity and botanical origin of propolis compounds active against bee pathogens using bioassay-guided fractionation against the bacterium Paenibacillus larvae, the causative agent of American foulbrood. Eleven dihydroflavonols were isolated from propolis collected in Fallon, NV, including pinobanksin-3-octanoate. This hitherto unknown derivative and five other 3-acyl-dihydroflavonols showed inhibitory activity against both P. larvae (IC50 = 17–68 μM) and Ascosphaera apis (IC50 = 8–23 μM), the fungal agent of chalkbrood. A structure-activity relationship between acyl group size and antimicrobial activity was found, with longer acyl groups increasing activity against P. larvae and shorter acyl groups increasing activity against A. apis . Finally, it was determined that the isolated 3-acyl-dihydroflavonols originated from Populus fremontii, and further analysis showed these compounds can also be found in other North American Populus spp. Graphical abstract: This work investigates the identity and botanical sources of propolis compounds important to bee health in North America. Six 3-acyl dihydroflavonols from Populus fremontii with differential activity against Ascosphera apis and Paenibacillus larvae were isolated from Fallon, NV, propolis. Further analysis showed these compounds have a variable distribution among other North American poplar species. Highlights: Isolated 3-acyl dihydroflavonols from propolis that inhibit bee pathogens. Discovered a structure-activity relationship related to antimicrobial selectivity. Determined that Populus fremontii was the botanical source of isolated compounds. Surveyed other North American Populus spp. resins for active compounds. Correlated specific poplar resin compounds with the activity of continental U.S. propolis.