![]() ![]() ![]() Compared to true comfrey ( Symphytum officinale ), species of comfrey such as Russian comfrey ( Symphytum x uplandicum ) and prickly comfrey ( Symphytum asperum ) contain the more toxic macrocyclic diester PAs (Hoffmann, 2003) and higher levels of echimidine, which has exhibited a more toxic effect (Gardner & McGuffin, 2013). PA levels also vary depending on the species of Symphytum. PA levels vary depending on the plant part used, with roots containing higher levels of PAs than mature leaves (Gardner & McGuffin, 2013 Mills & Bone, 2005). It is also important to know that some unsaturated PAs have been shown to be more toxic than others, with the macrocyclic retronecine diesters (e.g., senecionine) being more toxic than the retronecine monoesters (e.g., symphytine and echimidine) (Hoffmann, 2003 Rode, 2004). Saturated PAs are considered non-toxic, while unsaturated PAs are considered toxic (Hoffmann, 2003). Depending on their molecular structure, PAs can be either saturated (such as those found in arnica and echinacea) or unsaturated (such as those found in alkanet, borage, coltsfoot, and comfrey). While a number of plants contain PAs, such as alkanet ( Alkanna tinctoria ), arnica ( Arnica montana ), borage ( Borago officinalis ), coltsfoot ( Tussilago farfara ), comfrey ( Symphytum spp.), and echinacea ( Echinacea spp.), not all PAs are toxic. Despite this toxicity, scientific studies have also revealed that some types of PAs have several beneficial pharmacological properties, such as antimicrobial, anti-inflammatory, anti-cancer, and anti-HIV activity, as well as the ability to inhibit acetylcholinesterase enzyme (Moreira et al., 2018). Understanding Pyrrolizidine AlkaloidsĬertain types of pyrrolizidine alkaloids (PAs) are known hepatic and genetic toxins, and in some cases, respiratory toxins (Hoffmann, 2003). While comfrey is an herb with a long history of many different uses, its internal use has become quite controversial due to scientific studies, some dating back 40-60 years, that revealed potentially harmful effects of pyrrolizidine alkaloids (PAs) (Moreira et al., 2018), which are found in comfrey. A 2013 study concluded that a topical comfrey preparation probably eased osteoarthritis knee pain in a group of 220 participants (Cameron & Chrubasik, 2013). Its analgesic action could be due to its alkaloid content, but it could also be due to the astringent, anti-inflammatory, and demulcent properties as well. Because of this, it is often used to soothe hot, dry tissues, particularly those in the gastrointestinal, respiratory, and urinary tracts for digestive ulcers and diarrhea, coughs, or to ease symptoms associated with a urinary tract infection, respectively (Hoffmann, 2003 Tilgner, 2018).Ĭomfrey is sometimes used as a mild analgesic. While both comfrey leaf and root are well known for their mucilage content and associated demulcent action, the root is more demulcent than the leaf. ![]() Comfrey is even believed to help decrease inflammation of tendon sheaths (Tilgner, 2018), supporting its use for joint sprains. It is often used to slow bleeding and drainage from tissues and to tighten and tone relaxed tissues. ![]() In fact, topical applications of comfrey leaf can stimulate such prolific cell regeneration that it’s not recommended for use on deep wounds as it can promote surface-level tissue repair before the inner parts of the wound heal, thus creating an environment for bacterial growth and potential infection.Ĭomfrey leaf is also high in tannins, giving it astringent and anti-inflammatory properties. Comfrey leaf is prized for its allantoin content, making it useful for tissue repair and cell regeneration. ![]()
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