Artemisia comprises hardy herbaceous plants and shrubs with powerful chemical constituents in their essential oils. Its species grow in temperate climates of both hemispheres, usually in dry or semiarid habitats. Notable species include A. vulgaris (common mugwort), A. tridentata (big sagebrush), A. annua (sagewort) and A. absinthium (wormwood). The leaves of many species are covered with white hairs. The largest collection of living Artemisia species, subspecies and cultivars is held in the National Collection of Artemisia in Sidmouth, Devon, UK, which holds about 400 taxa.
Artemisia absinthium, otherwise known as common wormwood, is native to North Africa and temperate regions of Eurasia and is widely naturalized in Canada and the northern United States. It is a herbaceous perennial plant with fibrous roots. The stems are straight, grooved, branched and silvery-green, growing to 0.8-1.2 m tall. The leaves are covered with silky silvery-white trichomes and bear minute oil-producing glands. Wormwood herb contains bitter substances from the group of sesquiterpene lactones, and absinthin, at 0.20 to 0.28%, is the main component of these. The essential oil contains (-)-thujone, (+)-isothujone, thujyl alcohol and its esters, chamazulene and other mono- and sesquiterpenes.
At least nine different chemotypes of A. absinthium have been recognized based on essential oil compositions. Six different chemotypes of European A. absinthium have been noted, among them the (Z)-6,7-epoxyocimene, sabinyl acetate and β-thujone chemotypes. Croatian A. absinthium essential oil belongs to the (Z)-epoxyocimene and β-thujone chemotype, while French oil belongs to the (Z)-epoxyocimene and chrysanthenyl acetate chemotype. A. absinthium from Tajikistan represents a new chemotype, a myrcene/cis-chrysanthenyl acetate chemotype. The oils of Tajikistan are markedly different from those of European, Middle Eastern or other Asian locations. In these Tajik oils, β-thujone ranged from 0.4 to 7.3%. In a Tunisian study, leaf oil contained 30.41% chamazulene and 25.75% β-thujone, and flower oil contained 29.9% chamazulene and 19.66% β-thujone. Chamazulene is a blue oil with the molecular formula C₁₄H₁₆.
Thujone is a ketone and a monoterpene that occurs predominantly in two diastereomeric forms, (-)-α-thujone and (+)-β-thujone. Alpha and beta thujones are found in wormwood, most notably A. absinthium, usually as a mix of isomers in a 1:2 ratio. One chemotype does not produce β-thujone but does contain terpenoids not seen elsewhere. In the European Union the maximum thujone level is 35 mg/kg in alcoholic beverages prepared with Artemisia species. Only one case of documented toxicity of wormwood exists: a 31-year-old man drank 10 mL of steam-distilled pure volatile oil of wormwood, wrongly believing it was absinthe liqueur.
Uses in food and drink
A. absinthium is used to make the highly potent spirit absinthe. Absinthe is an anise-flavoured spirit made from several plants: the flowers and leaves of A. absinthium, green anise, sweet fennel and other medicinal and culinary herbs. When water is added, the components that dissolve poorly, mainly those from anise, fennel and star anise, leave solution and cloud the drink. The milky opalescence that results is called the louche. A. absinthium is also used in the food industry to make aperitifs, bitters and spirits.
Tarragon, A. dracunculus, is a culinary herb of particular importance in French cuisine. Tree wormwood, A. arborescens (sheeba in Arabic), is an aromatic herb of the Middle East, used in tea, usually with mint.
—
Related: Alpha Pinene · Angelica · Angelica Root · Angelica Root Oil · Barrenwort · Basil · Bay Leaf · Beachheather
