Response to #7

7. Symphytum officinale contains hepatoprotective constituents that help protect the liver from damage, these substances are not included in tests of this plant and would effect the outcome of these tests.

James Duke; United States Department of Agriculture Phytochemical and Ethnobotanical Database. (Search for all active constituents of S. officinale was conducted and included later in this report).
Search for Hepatoprotective and Anti-Tumor principles of Symphytum officinale

This data base shows at least five substances in comfrey that have a protective effect on the liver; they are Caffeic acid, Chlorogenic acid, Glucuronic acid, Lasiocarpine, and Rosmarinic acid. Caffeic acid has anti-hepatotoxic, anti-tumor, and hepatoprotective actions. Chlorogenic acid which has anti-cancer, anti-hepatotoxic, anti-mutagenic, anti-tumor, and hepatoprotective actions. Glucuronic acid is a anti-hepatotoxic, Lasiocarpine exhibits anti-tumor actions, and Rosmarinic acid is a anti-hepatotoxic.

Since Symphytum officinale has been used as animal feed and forage for centuries with safe results, it is likely that these hepatoprotective and anti-tumor qualities of the plant act to counter the plant's Pyrrolizidine alkaloids content. This is why the most damaging studies done on comfrey were conducted using Pyrrolizidine alkaloids isolated from the plant while disregarding the plant's significant liver protecting constituents that would have a profound effect on the results of the study.