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Analysis of herbal teas made from the leaves of comfrey (Symphytum officinale): reduction of N-oxides results in order of magnitude increases in the measurable concentration of pyrrolizidine alkaloids

Published online by Cambridge University Press:  02 January 2007

Nicholas H Oberlies ,
Nam-Cheol Kim ,
Dolores R Brine ,
Bradley J Collins ,
Robert W Handy ,
Charles M Sparacino ,
Mansukh C Wani  and
Monroe E Wall
Nicholas H Oberlies*
Affiliation:
Natural Products Laboratory, RTI International, PO Box 12194, Research Triangle Park, NC 27709, USA
Nam-Cheol Kim
Affiliation:
Natural Products Laboratory, RTI International, PO Box 12194, Research Triangle Park, NC 27709, USA Lovelace Respiratory Research Institute, Albuquerque, NM, USA
Dolores R Brine
Affiliation:
Health Sciences Unit, RTI International, Research Triangle Park, NC, USA
Bradley J Collins
Affiliation:
National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
Robert W Handy
Affiliation:
Health Sciences Unit, RTI International, Research Triangle Park, NC, USA
Charles M Sparacino
Affiliation:
Health Sciences Unit, RTI International, Research Triangle Park, NC, USA
Mansukh C Wani
Affiliation:
Natural Products Laboratory, RTI International, PO Box 12194, Research Triangle Park, NC 27709, USA
Monroe E Wall
Affiliation:
Natural Products Laboratory, RTI International, PO Box 12194, Research Triangle Park, NC 27709, USA
*
*Corresponding author: Email [email protected]
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Abstract

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Objectives:

To determine the relative quantities of two hepatotoxic pyrrolizidine alkaloids, symphytine and echimidine, in teas prepared from comfrey leaves (Symphytum officinale), and to determine the potential contribution of the N-oxide forms of these alkaloids to levels of the parent alkaloids.

Design:

Comfrey leaves were purchased from three commercial sources and used to prepare tea in a manner consistent with the methods used by consumers. An extraction scheme was devised for extraction of the alkaloids, and a gas chromatographic method was developed to quantify the two major alkaloids, symphytine and echimidine. Recognising that the N-oxide derivatives of these alkaloids have also been identified in comfrey preparations, chemical reduction was applied to determine the total quantities of the alkaloids as free bases and as N-oxide derivatives.

Results:

The concentration of symphytine and echimidine varied considerably between teas prepared from leaves purchased from the different vendors of plant material. Moreover, a much higher concentration of symphytine was found in the tea when steps were included to reduce N-oxides prior to analysis. The treatment of pure symphytine with hot water did not generate the N-oxide derivative de novo.

Conclusions:

Since the pyrrolizidine alkaloids are known to be hepatotoxic, consumption of herbal teas made from comfrey leaves may be ill-advised. The concentration of pyrrolizidine alkaloids in such teas may be underestimated substantially unless the concentration of N-oxides is taken into consideration.

Keywords

ComfreyPyrrolizidineN-oxideSymphytum officinaleSymphytineEchimidine
Type
Research Article
Information
Public Health Nutrition , Volume 7 , Issue 7 , October 2004 , pp. 919 - 924
Copyright
Copyright © The Authors 2004

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