Toxicity of mycotoxins to honeybees and its amelioration by propolis

Honeybees (Apis mellifera) and their resource-rich nests are hosts to a wide range of saprophytic fungi, including species that produce mycotoxins. The toxicity of aflatoxin B1 (AB1) and ochratoxin A (OTA), products of Aspergillus species often found in honeybee hives, was evaluated and LC50 values for both toxins were calculated. Workers can tolerate a wide range of concentrations of both OTA and AB1. At low concentrations, AB1 (1 mu g/g and 2.5 mu g/g diet) and OTA (1 mu g/g) did not have any apparent toxic effects on bees. Enhancement of the toxicity of AB1 by piperonyl butoxide (PBO), a known inhibitor of cytochrome P450 monooxygenases, indicates a role for P450s in AB1 detoxification in honeybees. Extracts of propolis, a complex mixture of plant-derived chemicals, including many flavonoids and other phenolic compounds, similarly ameliorated aflatoxin toxicity and delayed the onset of mortality. Collectively, these results suggest that tolerance of AB1 by honeybees may be due to P450-mediated metabolic detoxification. Propolis may serve a hitherto unrecognized role in honey bee health by enhancing the activity of P450 enzymes involved in mycotoxin detoxification.