In vitro growth-inhibitory effect of plant-derived extracts and compounds against Paenibacillus larvae and their acute oral toxicity to adult honey bees.
In total, 26 natural compounds of various chemical classes (flavonoids, alkaloids, terpenoids) and 19 crude extracts from selected plants were tested in vitro for antibacterial activity against three strains of P. larvae, the causal agent of American Foulbrood Disease of honey bees (AFB) by the broth microdilution method. Among the individual substances, sanguinarine (MIC 4 microg/ml), followed by thymoquinone, capsaicin, trans-2-hexenal and nordihydroguaiaretic acid (MIC 4-32 microg/ml) possessed the strongest antibacterial effect. In case of extracts, common hop (Humulus lupulus L.) and myrtle (Myrtus communis L.) methanolic-dichloromethane extracts exhibited the highest growth-inhibitory effect with MICs ranging from 2 to 8 microg/ml. Acute oral toxicity of the most active natural products was determined on adult honey bees, showing them as non-toxic at concentrations as high as 100 microg peer bee. Our study leads to identification of highly potent natural products effective against AFB in vitro with very low MICs compared to those reported in literature, low toxicity to adult honey bees and commercial availability suggesting them as perspective, low cost and consumer-acceptable agents for control of AFB.
Flesar
Jaroslav
J
Czech University of Life Sciences Prague, Faculty of Agrobiology, Food and Natural Resources, Department of Microbiology, Nutrition and Dietetics, Kamycka 129, Prague 165 21, Czech Republic.
Havlik
Jaroslav
J
Kloucek
Pavel
P
Rada
Vojtech
V
Titera
Dalibor
D
Bednar
Michal
M
Stropnicky
Michal
M
Kokoska
Ladislav
L
D000447:Aldehydes / Q000494:pharmacology; D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001516:Bees / Q000187:drug effects* / Q000382:microbiology; D053119:Benzophenanthridines / Q000494:pharmacology; D016227:Benzoquinones / Q000494:pharmacology; D002211:Capsaicin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005419:Flavonoids / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D009637:Masoprocol / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D056507:Paenibacillus / Q000187:drug effects* / Q000254:growth & development; D010936:Plant Extracts / Q000494:pharmacology*; D013729:Terpenes / Q000494:pharmacology
D000447:Aldehydes; D000470:Alkaloids; D000900:Anti-Bacterial Agents; D053119:Benzophenanthridines; D016227:Benzoquinones; D005419:Flavonoids; D007546:Isoquinolines; D010936:Plant Extracts; D013729:Terpenes; C051750:2-hexenal; D009637:Masoprocol; C005705:sanguinarine; C003466:thymoquinone; D002211:Capsaicin