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Upper Midwest Environmental Sciences Center

Fisheries Restoration

Evaluation of a method to determine eugenol concentrations in the edible fillet tissue from fish

Principal Investigator: Jeff Meinertz

Rainbow troutImpact of UMESC Science

The results from this study will provide the base for drug residue studies that are required by the U.S. Food and Drug Administration to evaluate the risk to people that might eat a recently sedated fish. These data will support the potential approval of an immediate release fish sedative that can be efficiently used by fishery managers throughout the U.S.


There is a critical need in U.S. fishery management programs and public aquaculture for an immediate-release sedative, i.e. a compound that would safely and effectively sedate fish to a handleable state allowing for their release immediately after sedation. The sedative would have applications for nearly all freshwater fish species during field procedures that involve handling of fish (e.g. data collection, spawning and tagging).

Currently, tricane methanesulphonate (MS-222) is the only fish sedative approved by the U.S. Food and Drug Administration (FDA). Use of MS-222 is constrained by a FDA imposed 21-day withdrawal period meaning fish exposed to MS-222 cannot be made available for human consumption for at least 21 days.

AQUI-S® 20E (AQUI-S® New Zealand Ltd., Lower Hut, New Zealand) is the candidate sedative that is currently being pursued for approval as an immediate-release sedative. Among the data the FDA will review when considering AQUI-S® 20E for approval are data describing the depletion of an AQUI-S® 20E primary residue (the marker residue, i.e. the parent compound, metabolite, or combination of residues that persist in the skin-on fillet tissue for an appreciable period of time) from the fillet tissue of exposed fish. The depletion studies will provide the data for the FDA to establish a withdrawal time for AQUI‑S® 20E ensuring all AQUI-S® 20E residues reach safe concentrations before fish become available for human consumption. To develop those data, a validated analytical method is needed to determine marker residue concentrations in the fillet tissue.

AQUI-S® 20E is comprised of 10% eugenol (the active ingredient) and 90% inert emulsifiers. A eugenol total residue depletion study was completed at UMESC. The data indicate that eugenol is the primary 14C-residue (>90% of all14C-residues) in extracts from fillet tissue taken from fish sampled immediately after the exposure (0 min) and from fish sampled at 30 and 60 min after the exposure (exposure = 10 mg/L 14C-eugenol for 60 min). In addition, the data indicated the depletion of 14C-eugenol residues from the fillet tissue was rapid (t1/2 = 26.25 min) after transferring the exposed fish to fresh flowing water.  Because eugenol was the primary residue and persisted as the primary residue for an appreciable amount of time, eugenol will be presumed to be selected by the FDA as the marker residue for AQUI‑S® 20E.

A method to determine eugenol concentrations in fish fillet tissue has been developed. The method will undergo comprehensive validation as a determinative method following guidance in FDA Guidance for Industry #3, “General principles for evaluating the safety of compounds used in food-producing animals.”  A safe concentration of 400 µg/g eugenol in fish fillet tissue has been established by the FDA (INAD submission I-011475-H-0012-OT). This safe concentration applies only to the use of AQUI-S® 20E during fishery management activities. A tolerance concentration has not been established. Results from recently completed studies at UMESC indicated that eugenol concentrations in fish fillet tissue do not approach the safe concentration of 400 µg/g. The greatest concentrations generated in fillet tissue, even after extreme exposure conditions, were near 60 µg/g. Therefore, because a tolerance concentration for eugenol has not been established and fillet tissue concentrations will most likely never exceed 60 µg/g, we are proposing to validate the method for determining eugenol concentrations in fillet tissue as a determinative method at concentrations ranging from 0.15 to 60 µg/g.


To evaluate the method used to determine the residue of eugenol in the edible fillet tissue of rainbow trout after exposure to AQUI-S® 20E for future FDA safe concentration determinations.


Meinertz, J.R., S.L. Greseth, T.M. Schreier, J.A. Bernardy, and W.H. Gingerich.  2006.  Isoeugenol concentrations in rainbow trout (Oncorhynchus mykiss) skin on fillet tissue after exposure to AQUI-S® at different temperatures, durations, and concentrations.  Aquaculture 254: 347-354.

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