General Description

Epilobium is a genus of some 200 species that typically grow at relatively high latitudes or high altitudes.¹ This perennial is found in all parts of the world. It has tall, erect, and somewhat woody stems, from 2 to 7 ft tall, crowded with long, narrow, alternate leaves that are from 2 to 6 in long. Its flowers range from lavender to pink to carmine-purple, and its pods are long, narrow, and filled with feathery seeds.² Most species have small flowers (e.g., Epilobium parviflorum, known as small-flowered willow herb). A few have large flowers (e.g., E. angustifolium, known as great willow herb). Despite the use of the term “willow,” there is no relationship between Epilobium spp. and Salix spp. (willow).

Chemical Composition

The aerial parts are rich in flavonoids³ and flavonol glycosides based on kaempferol, quercetin, and myricetin skeletons.⁴ The plants contain complex tannins such as ellagitannins (oenothein A and B) and gallotannins⁵; β-sitosterol; triterpenes⁶; and gallic, chlorogenic, and ellagic acids.⁷ In the small-flowered species, myricetin is the predominant flavonoid. The large-flowered species have a completely different flavonoid pattern, with isoquercitrin being predominant. The plant contains the highest content of the flavonoid myricetin 3-0-β-D-glucuronide shortly after flowering (Figure 89-1).

FIGURE 89-1 Quercitrin.

History and Folk Use

Fireweed has been widely used as a medicine and as a food in many parts of the world. Native Americans used it for burning urination, male urination problems, coughs and sore throats, stomachaches and intestinal discomfort, bowel hemorrhages, gastritis, tuberculosis, and as a panacea for pain.⁸ It was used as a poultice for boils; abscesses; carbuncles; bruises; infected sores, cuts, and wounds; and other skin ailments. Various Eskimo and Siberian tribes also used the plant to treat sores.⁹ Young shoots were widely consumed as food and fodder, as were the roots and leaves. The seed fluff was used for weaving cloth, making thread, and starting fires. Fireweed is named mjoelke in Scandinavia, a derivation of the word milk, because of centuries of observation that cows grazing on the plant produce more milk.

Eclectic physicians considered fireweed unequaled as a treatment for summer bowel troubles and also used it in other types of diarrhea, including cholera infantum and typhoid dysentery.¹⁰ The Eclectics often administered fireweed as an infusion, using frequent small doses (up to every 10 minutes). E. hirsutum was used in Egyptian and European folk medicine to treat inflammation, adenoma, and prostate tumors.¹¹ Europeans also used the plant to treat eczema, seborrhea, other skin conditions, and menstrual disorders.¹² The plant was also used for the treatment of benign prostatic hyperplasia.¹³

Pharmacology

Analysis of studies on fireweed is complex, given the subtle differences among species and differences in the actions of aqueous and alcoholic extracts. Overall, most fireweed species appear to have analgesic, antidiarrheal, antiinflammatory, antimicrobial, antineoplastic, and prostate-related activities.