Medicinal Value of Comfrey Root Bark
Answered by: Conrad Richter
Question from: Tom Chung
Posted on: September 22, 1999

I want to harvest a wonderful patch of comfrey root. I was instructed to remove the dark outer bark before drying in order to attain a very smooth powder. Will I lose any significant amount of the medicinal properties?

We are not aware of any studies to localize the medicinal components in comfrey roots. All of the chemical analysis studies we are aware of were done on whole root.

In the absence of scientific evidence, we can only guess from indirect evidence the importance of the rootbark. It is worth noting that the rootbark is the most medicinally active part in some herbs. Before drying these herbs, the rootbark is separated from the root. In the case of comfrey, the whole roots are considered medicinal, and users are not normally instructed to separate the rootbark before drying. This may suggests that both the root cortex and the rootbark contribute to the medicinal effect.

The main medicinal components of the root are allantoin, a hormone-like cell-proliferant that promotes cell division and speeds healing, and mucilage. The mucilage likely comes from the cortex of the root. Mucilage is important in providing a soothing cover over inflamed and damaged tissue. Allantoin could be concentrated in the rootbark, or both the bark and the cortex – there is no way of knowing without proper analyses.

The harvest season is critical for the allantoin content. Allantoin is maximal (up to 0.8% by dry weight) in roots during the winter and early spring months before comfrey regrows from the roots. Once the leaves appear, it appears that allantoin is redistributed from the roots to the above-ground parts. By mid-summer, the allantoin level in the roots drops to almost nil. For this reason, roots should be harvested in the late fall after the frosts have killed back the leaves.

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