Artemisia is an aromatic plant found as a pervasive weed in China. It is thus found both in wild and is also cultivated. It is a single-stemmed, hairless, sweetly aromatic annual growing to a height of 1 m. The stem is erect, ribbed, brownish, or violet brown in colour with very slender and glabrous branches. Leaves are fern-like, 3-pinnatisect, 3–5 cm long, 2–4 cm wide with upper leaves being 2-pinnatisect, smaller and sessile. Inflorescence is a compound raceme with the tiny flower heads being inconspicuous greenish or yellowish, globose, 2–2.5 mm in diameter having a camphor-like scent. Flowers are hermaphrodite, disciform, and made up of outer filiform florets (female) and inner disc like bisexual florets. The involucre of bracts around the flower head are over lapping and hairless. Outer bracts are green, linear-oblong with inner bracts shiny and oval in shape. Fruit is a yellow to brownish, small and thin-walled cypsela, 0.6–0.8 mm long, with a shiny surface marked with vertical grooves and bears a single seed. Oil glands are present on leaves, stems, and florets.

Constituents

The plant yields a sweet-smelling essential oil of about 0.01–0.5% composed of camphor (44%), germacrene (16%), trans-pinocarveol, β-selenin (9%), β-caryopyllene (9%), artemisia ketone (3%), α-terpinene, β–phellendrene, 1,4-cineole, 1,8-cineole, β–thujone, nerol, α–phenanthrene, citral, chamazulene, and citronellal. The concentration and composition of the volatile oil is dependant on the drug source with the Chinese chemotype being rich in irregular monoterpenes like artimisia ketone and Vietnamese chemotype being rich in germacrene and camphor.

Search for effective anti-malarials in the 1970s resulted in the isolation of artemisinin, a bitter sesquiterpene lactone. Called “Quinghaosu,” chemically it has a 1, 2, 4-trioxane structure with a unique endo-peroxide bridge without a nitrogen containing ring system. The endoperoxide moiety is essential for activity. It is isolated in the yield of 0.06–0.16% from the aerial parts with artemisinic acid (0.4%), dihydroartemisinin, arteannuin A & B (0.1%) as the other sesquiterpene constituents.

The plant contains several methylated flavonoids—artemetin, chrysosplenetin, quercetagetin, eupatorin, and castian.