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Parthenolide content of Canadian commercial feverfew preparations: label claims are misleading in most cases

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Andrew H. Draves BScPharm, BSc, is a community pharmacist in Barrie, Ontario. Scott E. Walker, MScPhm is the research coordinator, Department of Pharmacy, Sunnybrook & Women's College Health Science Centre, and an Associate Professor at University of Toronto. Contact: [email protected]

Background: The popularity of herbal supplements has been growing dramatically in North America. Concerns about the consistency of the products being consumed has resulted in many herbal supplement producers guaranteeing the content of marker compounds.

Objective: To investigate the accuracy of label claims on commercially prepared feverfew preparations and quantify parthenolide content.

Design: Liquid chromatography was used to quantify the parthenolide content of commercially purchased feverfew preparations. Following extraction into a methanol and water solution (50:50), the parthenolide concentration was determined by liquid chromatography with UV detection at 214 nm.

Results: A large variance in total parthenolide content in the commercial preparations was observed, ranging from below the Limit of Quantification (LOQ) of 21 [Symbol Not Transcribed] [mu]g to 996.3 [Symbol Not Transcribed] [mu]g per dosage unit. Tablets varied from a low of 40.4 [Symbol Not Transcribed] [mu]g to a high of 546.3 [Symbol Not Transcribed] [mu]g and percentages of label claim from 16.1% to 218.5%.

Tablet lot-to-lot variation varied from a CV% of 7.2 to 46.6%. Capsules had parthenolide contents that varied from <21.0 to 996.3 [Symbol Not Transcribed] [mu]g and percentage of label claim varying from <8.4 to 446.3%. Lot-to-lot variation ranged from a CV% of 4.5-84.9%. Only three of the tinctures tested had parthenolide content above the LOQ of 2.1 g/mL, and they ranged from 89.0 to 3535.1 [Symbol Not Transcribed] [mu]g. The tinctures did not make label claims of parthenolide content and only one of the three that had parthenolide content above the LOQ could be accurately measured due to the presence of co-eluting compounds. Two...