Planta Med 2009; 75 - PJ95
DOI: 10.1055/s-0029-1234900

Thymoquinone is active in vitro against P. larvae and exhibits low toxicity against adult honey bees

J Flesar 1, J Havlik 1, P Kloucek 1, M Stropnicky 1, 3, D Titera 3, L Kokoska 2, V Rada 1
  • 1Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, Kamycka 129, Prague 6, 165 21, Czech Republic
  • 2Institute of Tropics and Subtropics, Czech University of Life Sciences Prague, Kamycka 129, Prague 6, 165 21, Czech Republic
  • 3Bee Research Institute at Dol, Libcice nad Vltavou, 252 66, Czech Republic

American foulbrood (AFB) is a serious worldwide spreading disease of honeybees caused by the spore-forming, Gram-positive bacterium Paenibacillus larvae. Antimicrobial natural products may provide a safe and acceptable alternative in prevention and treatment of AFB. The inhibiting action of thymoquinone (TQ) on P. larvae was previously studied in vitro [1] (MIC 8–16µg/mL). Laboratory and field trials were conducted to evaluate the acute oral toxicity and transfer of TQ to royal jelly or to honey. We determined in vivo acute oral toxicity on adult honey bees by technique ICBR (1993) [2], expressed as LD50. The defined amounts of TQ were dissolved in a feeding solution (50% v/v sucrose in distilled water). The second experiment transfer to royal jelly was conducted from September to October. Non-toxic dose of TQ was fed on honey bee colony. Amount of TQ was given with the aid of GC-MS methods.

LD50 value of thymoquinone was higher than 50µg per bee and would be classifying according to results as slightly or non-toxic compound. TQ occurred in royal jelly in concentrations potentially useful for application against P. larvae.

Acknowledgements: This research was supported by grants NAZV QH72144, CIGA 20082012 and GACR (No. 525/08/H060).

References: [1] Flesar, J. et al. (2008) Planta Med. 74:1135.

[2] ICPBR (1993) Hazard of Pesticides to Bees. Wageningen, The Netherlands.