Artemisia absinthium

Description and background

Artemisia absinthium of the Asteriaceae or Compositae family, other names: Absinth(e), Wormwood, Common wormwood, Absinthii herba. Not to be confused with Artemisia annua (Sweet wormwood).  

Artemisia abinthium is a perennial plant, which grows as a small bush with feathery leaves and pale yellow flowers.  The applicable parts are those that are above ground. (NMD 2022) The plant is native from Europe to Siberia and Western Himalaya but is now found in other countries including Australia and India (POWO 2022) and across the northern United States and in Canada (US Forestry Service). The medical use of the wormwood plant dates back to at least Roman times and it was used as an anthelmintic (for removal of intestinal worms) and purgative, gradually becoming a general remedy for various diseases (Lachenmeier 2010). Use as a ‘cure-all’ continued through to the 19^th century. The adoption of wormwood-flavoured alcoholic extracts and distillates as aperitifs as well as patent medicine led to large scale production and mass use. Chronic use was linked with a syndrome known as absinthism consisting of addiction, hyperexcitability, epileptic fits and hallucination (although this has since been disputed) and this led to a decline in use (Lachenmeier 2010). Interest in the plant was renewed due to research in conditions such as Crohn’s disease (Krebs 2010) and stroke (Bora 2010). These have not, however, been replicated.

No data are available on the prevalence of use in cancer patients.

Ingredient and quality issues

Wormwood’s aerial parts contain bitter principles (absinthin and anabsinthin), resins and organic acids. A volatile oil is present the composition of which has been found to vary with the largest part formed by monoterpenes. In some cases, the oil contains between 10% and 90% of thujone (a monoterpene ketone) which has been linked to adverse and toxic effects (Lachenmeier 2010; Judpentiene 2004). High concentrations of other monoterpenes including myrcene, and trans-sabinyl acetate have also been identified.

Alleged indications

Traditional use is based on wormwood as a bitter tonic for digestive disorders and loss of appetite. It is promoted as a sedative and anti-inflammatory and for external use for wounds, ulcers, skin blotches and insect bites. The European Medicines Agency Committee on Herbal Medicinal Products (HMPC) concluded that, on the basis of its long-standing use, wormwood herb preparations can be used for temporary loss of appetite or for mild heartburn and stomach/gut disorders (HMPC 2017, 2020).

In the context of cancer, A. absinthium has been investigated in in vitro studies for its potential cytotoxic effects.

Mechanisms of action

Wormwood has bactericidal, insecticidal and vermicidal activity mainly due to the thujone oils (Blagojevic 2006; Lopes-Lutz 2008). The thujone constituent is also a central nervous system stimulant which acts by modulating gamma-aminobutyric acid (GABA) type A receptors. However, this effect is more closely linked with observed toxic effects of wormwood (Lachenmeier 2010). Wormwood has been reported to reduce levels of tumour necrosis factor α (TNF-α), and may have a beneficial effect in a range of conditions influenced by pro-inflammatory cytokines such this (Krebs 2009; Krebs 2010).

In vitro studies in breast cancer and leukaemia cell lines indicate anti-proliferative activity together with promotion of apoptosis (programmed cell death) (Shafi 2012; Wegiera 2012). Crude extracts of the above ground parts of the plant have been reported to have induced anti-proliferative effects on human breast cancer cells which could possibly trigger apoptosis (Shafi 2012). A pilot study in leukaemia cell lines found that various plants from the Asteraceae family induced cell death by apoptosis but the correlation between polyphenol content and activity was inconsistent (Wegiera 2012). Subsequent in vitro studies have reported various anticancer effects in breast cancer cells including apoptosis and suppression of proliferation (Mughees 2020), and reduced migration and viability (Moacă 2019). Effects on apoptosis have also been observed in human colorectal cancer cells (Nazeri 2020) and liver cancer cells (Wei 2019). Migration and viability of melanoma cells were reduced (Moacă 2019) but proliferation of colorectal cancer cells appeared unaffected (Sultan 2020) by Artemisia absinthe extracts.

Application and dosage

There is no documented safe or effective dose for the use in treatment of cancer. Traditionally, wormwood has been used orally and topically. Based on traditional use, in temporary loss of appetite and mild dyspeptic/gastrointestinal disorders, a tea or tincture has been used containing the equivalent of 2-3g of the herb divided into 2 or 3 doses orally for not more than 2 weeks (HMPC 2020). Typical doses for other therapeutic uses are not available but the European Medicines Agency has advised that, due to potential for neurotoxicity, chemotypes with low content of thujone are preferred and the intake of thujone should not exceed 6 mg/day (HMPC 2020). Wormwood above ground parts have been used in flavouring alcoholic drinks including absinthe but use was banned in many countries due to toxicity related to thujone. Many countries now regulate absinthe and either specify maximum content of thujone or that absinthe should be thujone free.

Legal issues

Wormwood was classified as an unsafe drug and banned in many countries including the USA although "thujone-free" wormwood extract has been approved by the US Food and Drug Administration (FDA) for use in foods and as a flavouring in alcoholic drinks (Bora 2010). In Europe, Artemisia absinthium L. has been recognised by the European Medicines Agency as a herb for which use is based on traditional use (HMPC 2020).