ABSTRACT
Although comfrey has been one of the most common herbs sold to the American public over the past thirty years, there is reason to believe that using it internally is definitely hazardous to the health. All comfrey species investigated have been found to contain hepatotoxic pyrrolizidine alkaloids (PAs), but the literature on the subject is confused due to a glaring lack of attention to proper botanical identification of the various Symphytum species studied. Common comfrey contains principally 7-acetylintermedine and 7-acetyllycopsamine in addition to their unacetylated precursors and symphytine. It does not contain high levels of echimidine, probably the most toxic comfrey PA. Echimidine has been identified, along with symphytine and six other PAs, in Russian comfrey. Russian comfrey was heavily promoted in the back-to-the-land movement, and most of the comfrey cultivated in home gardens is the Russian hybrid. The former alkaloid is also present in prickly comfrey. Comfrey root contains about ten times the concentration of PAs found in the leaves.12,13
Using echimidine as a marker, it becomes relatively easy to determine if samples of common comfrey are properly labeled. A Canadian study of thirteen commercial samples labeled either "comfrey" or "comfrey/Symphytum officinale" revealed that six of them contained echimidine and were therefore probably not derived from common comfrey (S. officinale) but from prickly comfrey (5. asperum) or Russian comfrey (S. x uplandicum).14 Products containing echimidine are barred from sale in Canada for medicinal purposes, but, lacking chemical analysis, this cannot be determined accurately because the commercial labeling is so unreliable. However, the specific prohibition against echimidine products should not cause anyone to underestimate the potential danger of common comfrey that
does contain other hepatotoxic PAs. All comfrey root-containing prod ucts are no longer acceptable in Canada.
