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United States Department of Agriculture

Agricultural Research Service

Title: Laboratory Studies on the Photostability of Fumagillin, the Active Ingredient of Fumidil B

item Kochansky, Jan

Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 19, 2003
Publication Date: August 19, 2003
Citation: Kochansky, J.P., Nasr, M. 2003. Laboratory studies on the photostability of fumagillin, the active ingredient of fumidil b. Apidologie.

Interpretive Summary: Nosema is a serious disease of honey bees, leading to bee mortality and decreased honey production and pollination efficiency. There have been reports that the only antibiotic registered for control of nosema is ineffective when exposed to sunlight. We investigated the stability of this antibiotic when exposed to light and found that while the compound was rapidly transformed to a mixture of products, the product mixture exhibited no decrease in activity against nosema. This information is of primary interest to scientists and commercial and hobbyist beekeepers.

Technical Abstract: Fumagillin (as the dicyclohexylammonium salt) has been found to be extremely unstable when solutions in 50% ethanol are exposed to sunlight in small vials, undergoing a series of degradations with half-lives in the range of seconds to minutes. Similar results were obtained with photolyses of Fumidil B in either 50% ethanol or sugar syrup. Decomposition also occurred in fluorescent room light. The reactions involved in the photolyses are apparently reversible Z/E rearrangements in the unsaturated ester portion of the molecule, and do not involve the pharmacologically active part. Samples of fumagillin in syrup, irradiated for 0, 0.5, 5, 30, or 360 minutes were all effective in protecting caged bees from Nosema. While long exposures to sunlight should be avoided, brief exposure to sunlight causes no notable loss of activity.

Last Modified: 4/22/2015
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