The Medicinal Plant Comfrey
By: David Lieu


Gardensoyvey. Permission Pending from http://www.gardensoyvey.com/catalog/images/comfrey-close.jpg

Table of Contents

Introduction

Comfrey has been around for centuries. It dates back all the way to 400 B.C. when the Greeks used it to stop severe bleeding and bronchial problems. It has also been mentioned in many books that have been writing by famous people such as the Greek historian Herodotus and the Roman naturalist Pliny the Elder who lived centuries apart. Since then comfrey has been used in almost every culture and society and in very many different ways. There are numerous benefits in using the herb which is too long to list here and I have listed below. At first glance this seem to be the miracle drug which could do away with all aliments and sicknesses. It was at one point even thought by some to end world hunger. It hasn't been till the past few decades that scientist have found some questionable chemicals in comfrey. Many toxins and carcinogens have been identified in its leaves and roots. Chemicals like pyrrolizidine alkaloid, which is a toxin and Symphytine, which is thought to be a carcinogen. There are still conflicting results depending on where you are getting your information. Some countries like Australia have band the plant all together. A few reports claim that there is so little concentration of the toxins and carcinogens in the plant that it would be very unlikely that someone could die from eating comfrey. A few reports even go out on a limb and say how much you would have to eat to die. No matter what the results are people are probably going to still be eating and drinking comfrey like they have been for centuries until some hard substantial evidence can be found to support the idea that you can die from eating comfrey.[8]


General Information

Common Names: Knitbone. Knitback. Consound. Blackwort. Bruisewort. Slippery Root. Boneset. Yalluc (Saxon). Gum Plant. Consolida. Ass Ear.[2] [5]

Scientific Name: Symphytum officinale.[2] [5]

Parts Used: The parts of comfrey that are usually used in different remedies are the roots, rhizomes and leaves.[3]

Habitats: Comfrey prefers to grow in banks of rivers and ditches and any other wet and moist places. Comfrey also prefers the shady areas.[4]

Cultivation: Comfrey can grow in any kind of soil and favors the shade of trees. To propagate the plant all that is needed is to take a little bit of the root and this will produce a new plant. They grow very easily in most location so it is very difficult to get rid of comfrey once it has entered an area where it is not wanted.[4]

Locations: Comfrey is native to Europe and temperate Asia but can be found in many other places around the world including the United States in woodlands and on riverbanks.[2]


Picture Pending Permission by USDA from http://plants.usda.gov/java/profile?symbol=SYOF

Picture courtesy of Camilla Fox from www.livejournal.com/users/cfox/43379.html

Medicinal Effects:

Pharmalogical effects: The active ingredient in comfrey is thought to be Allantoin which helps to speed up and repair damaged tissue. It is usually used for a wide variety of things such as bruises, sprains, dislocations, soar throat, stomach ache, ulcers, rheumatism, chest congestion, diarrhea, inflammation of the lungs, fractured, broken, painful or crumbling bones, as well as inflamed, arthritic joints and any traumatized or injured bones. If these things actually work is not very well known. In the case of what comfrey is used for has been changed from century to century. The list above is a list of ailments that I have found. It started out as a a paste that was made to stop severe bleeding and as well as problems in the lungs. Some how along the way it was discovered that it could help heal broken bones when applied externally and let to dry. This formed a makeshift cast which prevented the movement of the particular limb. It was later on thought to cure many stomach ailments as well and can be taking as a tea or cooked into a honey like viscous substance. Comfrey can be used both externally and internally.[5] [6] [8]

Adverse effects: Comfrey is known to contain trace amounts of carcinogens and toxins which have been discovered in just recent decades. If taken in large quantities there could be a slight possibility of poisoning. Tests on mice have shown a number of these adverse effects. However in these experiments the concentration is at much higher doses and also taking into consideration the different metabolisms of a mouse verus that of a human. Some studies show that it is very unlikely to intake enough of the plant to cause these adverse effects in humans. It has been agreed upon by most doctors and scientists that the ointments made from comfrey may be used on the skin should not be use for no more than a couple weeks at a time. Also comfrey should not be taken during pregnancy or while breastfeeding because the toxins and carcinogens may have a number of adverse effects on the unborn fetus or a new born baby with a very weak immune system.[5] [7]

Chemical Information:

Chemical names: Allantoin, Urea or 2,5-Dioxo-4-imidazolidinyl is thought to be the active ingredient in comfrey which is primarily found in its highest concentration (~0.6%) in the roots.[4]

Chemical structure:


This is a 2D structural drawing of Allantoin by me in Chemsketch. Allantoin is found with both R and S sterocenters.



This is a 3D optimized ball and stick model of Allantoin by me in Chemsketch

Isolation and Synthesis:

Isolation: While working on the degradation of xanthine in young and aged leaves of immature and mature fruit of Coffea arabica and Coffea dewevrei the Universidade Estadual de Campians found considferable levels of endogenous allantoin and allantoic acid in the fruits and leaves. In a different experiment by the Ochanomizu University Department of Biology on the biosynthesis and catabolism of caffeine they found allantoin as part of the specific pathway for the production of caffeine. So historically the leaves and roots of the comfrey plant were used to produce their medicines which is probably true since the active compound allantoin has been found in a number of other plants and if it is a product of the catalysis of urea then there should be many more plants that contain allantoin. The main difference is that comfrey contains a substatial amount of allantoin.[13] [14]

Synthesis: The synthesis of Allantoin is a very confusing and multi-step process. The University of Missouri-Columbia's Department of Biochemistry has thought to have finally delineate the production pathway. It is still not entirely understood, however experiments have shown that Allantoin is syntheszed by Urea. Urea goes through a oxygen dependant oxidation with the help of the catalytic enzyme urate oxidase. This then produces substantial intermediates called 5-hydroxyisourate and hydrogen peroxide. The rest of the production pathway for this compound is occurs nonenzymatically. It begins with the hydrolysis of the N1-C6 bond and then an unusual 1,2-carboxylate shift and decarboxylation. This then forms allantoin along with carbon dioxide. The Massachusetts Institute of Technology Department of Chemistry has however found a number of other minor trace products formed from 5-hydroxisourate such as spirodihydantoin, spiroiminodihydantoin and guanidinohydantoin, which are significantly different from allantoin.[10] [11]



This is a simplfied mechanism of the production of allantoin. Permission requested.[10]

Interesting Facts and Figures:

Facts: Pyrrolizidine alkaloid has been isolated from Comfrey and in high concentrations can be toxic and cause liver damage. To die from eating comfrey one would have to consume 66,300 comfrey leaves which is more than a person's body weight in leaves. Symphytine is the carcinogen found in Comfrey but is only 5% of the total alkaloids in comfrey. Comfrey also makes a very good green fertilizer. In Latin the name Symphytum is derived from the Greek word meaning to unite and the current name Comfrey is derived from the phrase "con firma" or "making firm".[1] [6]

Figures:

Bibliography:


[1] Henriette's Herbal Homepage: The Medicinal HerbFAQ 2.15 Comfrey hepatotoxicity Retrieved February 27, 2007, from http://www.henriettesherbal.com/faqs/medi-2-15-comfrey.html

[2] Botanical.com: A Modern Herbal Retrieved February 27, 2007, from http://botanical.com/botanical/mgmh/c/comfre92.html

[3] Wildcrafted Herbal Products: Comfrey (Symphytum officinale) Retrieved February 27, 2007, from http://www.wildcrafted.com.au/Botanicals/Comfrey.html

[4] NewCROP: Comfrey Retrieved February 27, 2007, from http://www.hort.purdue.edu/newcrop/afcm/comfrey.html

[5] PDRHealth: Comfrey Retrieved February 27, 2007, from http://www.pdrhealth.com/drug_info/nmdrugprofiles/herbaldrugs/100840.shtml

[6] Akamuti: Plant Profile Comfrey (Symphytum officinalis) Retrieved February 27, 2007, from http://www.akamuti.co.uk/Comfrey.htm

[7] GardenWEB: Comfrey - The Facts Retrieved February 27, 2007, from http://forums2.gardenweb.com/forums/load/herbal/msg080635098259.html?23

[8] Herbal Legacy: History of Comfrey Retrieved February 27, 2007, from http://www.herballegacy.com/history295.htm

[9] Natural Resource Conservation Services: Plants Profile Comfrey Retrieved February 28, 2007, from http://plants.usda.gov/java/profile?symbol=SYOF

[10] Kahn, K.; Serfozo, P.; Tipton, P. A.J. Am. Chem. Soc.; (Article); 1997; 119(23); 5435-5442. "Identification of the True Product of the Urate Oxidase Reaction" http://mutex.gmu.edu:2106/10.1021/ja970375t

[11] Yu, H.; Niles, J. C.; Wishnok, J. S.; Tannenbaum, S. R. Org. Lett.; (Letter); 2004; 6(19); 3417-3420. "Spirodihydantoin Is a Minor Product of 5-Hydroxyisourate in Urate Oxidation" http://mutex.gmu.edu:2106/10.1021/ol048547w

[12] Lin, Y.-L.; Tsai, Y.-L.; Kuo, Y.-H.; Liu, Y.-H.; Shiao, M.-S. J. Nat. Prod.; (Article); 1999; 62(11); 1500-1503. "Phenolic Compounds from Tournefortia sarmentosa" http://mutex.gmu.edu:2106/10.1021/np9901332

[13] Ashihara, H.; Crozier, A.J. Agric. Food Chem.; (Article); 1999; 47(8); 3425-3431. "Biosynthesis and Catabolism of Caffeine in Low-Caffeine-Containing Species of Coffea" http://mutex.gmu.edu:2106/10.1021/jf981209n

[14] Vitoria, A. P.; Mazzafera, P.J. Agric. Food Chem.; (Article); 1999; 47(5); 1851-1855. "Xanthine Degradation and Related Enzyme Activities in Leaves and Fruits of Two Coffea Species Differing in Caffeine Catabolism" http://mutex.gmu.edu:2106/10.1021/jf980892a

Web Search Log

Home Page
Personal Page
CHEM 350 Projects
GMU Links
Off-Campus Links
GMU Chemistry Department
CHEM 350 Course Website