Best studies on comfrey:  properties, phytochemistry.

A Symphytum officinale Root Extract Exerts Anti-inflammatory Properties by Affecting Two Distinct Steps of NF-κB Signaling.
Seigner J, Junker-Samek M, Plaza A, D'Urso G, Masullo M, Piacente S, Holper-Schichl YM, de Martin R.
Front Pharmacol. 2019 Apr 26;10:289. doi: 10.3389/fphar.2019.00289

Tolerability and effectiveness of an antitrauma cream with comfrey herb extract in pediatric use with application on intact and on broken skin.
Kucera A, Barna M, Holcova S, Horacek O, Hladiková M, Ottillinger B.
Int J Pediatr Adolesc Med. 2018 Dec;5(4):135-141. doi: 10.1016/j.ijpam.2018.11.002.

Ethnoveterinary contemporary knowledge of farmers in pre-alpine and alpine regions of the Swiss cantons of Bern and Lucerne compared to ancient and recent literature - Is there a tradition?
Stucki K, Cero MD, Vogl CR, Ivemeyer S, Meier B, Maeschli A, Hamburger M, Walkenhorst M.
J Ethnopharmacol. 2019 Apr 24;234:225-244. doi: 10.1016/j.jep.2018.12.022.

Physicochemical properties and activities of comfrey polysaccharides extracted by different techniques.
Duan M, Shang H, Chen S, Li R, Wu H.
Int J Biol Macromol. 2018 Aug;115:876-882. doi: 10.1016/j.ijbiomac.2018.04.188.

Extraction condition optimization and effects of drying methods on physicochemical properties and antioxidant activities of polysaccharides from comfrey (Symphytum officinale L.) root.
Shang H, Zhou H, Duan M, Li R, Wu H, Lou Y.
Int J Biol Macromol. 2018 Jun;112:889-899. doi: 10.1016/j.ijbiomac.2018.01.198.

Is comfrey root more than toxic pyrrolizidine alkaloids? Salvianolic acids among antioxidant polyphenols in comfrey (Symphytum officinale L.) roots.
Trifan A, Opitz SEW, Josuran R, Grubelnik A, Esslinger N, Peter S, Bräm S, Meier N, Wolfram E.
Food Chem Toxicol. 2018 Feb;112:178-187. doi: 10.1016/j.fct.2017.12.051.

Comfrey and Buttercup Eaters: Wild Vegetables of the Imereti Region in Western Georgia, Caucasus.
Łuczaj Ł, Tvalodze B, Zalkaliani D.
Econ Bot. 2017;71(2):188-193. doi: 10.1007/s12231-017-9379-x.

Proliferative and antioxidant activity of Symphytum officinale root extract.
Sowa I, Paduch R, Strzemski M, Zielińska S, Rydzik-Strzemska E, Sawicki J, Kocjan R, Polkowski J, Matkowski A, Latalski M, Wójciak-Kosior M.
Nat Prod Res. 2018 Mar;32(5):605-609. doi: 10.1080/14786419.2017.1326492.

Comfrey (Symphytum officinale L.) is a perennial plant that belongs to the Boraginaceae family.

It reaches a height of 90 centimeters, large and hairy leaves, purple or white flowers.

Active components of the root of the Comfrey  are the compound of amino (allantoine), phenolic acids (rosemary acid, salicylic and caffeic), mucillosis polysaccarids and glicopeptids. Rosemary acid and root-isolated glicopeptids have been shown to have anti-inflammatory activity. In particular, rosemary acid inhibits the synthesis of prostaglandins and glycopeptids, at a dependent dose, inhibit the release of prostaglandins (1).

The root is used to treat inflammation of the skin and leg ulcers. It is not used internally because of its content of pyrolizidic alkaloids which demonstrates hepatotoxic, carcinogenic and mutagenic properties in rats (2).

Comfrey more studies

References_____________________________________________________________________

(1) European Scientific Cooperative on Phytotherapy. Symphyti radix. 2nd ed. Supplement. New York: Thieme; 2009. ESCOP Monographs; pp. 249–54.

(2) Schulz V, Hänsel R, Blumenthal M, Tyler VE. Rational phytotherapy. Berlin Heidelberg: Springer-Verlag; 2004. pp. 335–47.