Noble yarrow

The dominant volatile in most reported Achillea nobilis oils. α-Thujone contributes to the plant's aromatic, bitter character and antimicrobial and anthelmintic actions, but it is a GABA-A receptor antagonist and neurotoxin/convulsant at higher doses, which is the principal safety concern limiting internal use of the essential oil.

An expectorant and mucolytic monoterpene with documented anti-inflammatory and antimicrobial activity; contributes to the camphoraceous odour and to the herb's traditional use for respiratory and abdominal complaints.

A characteristic ketone of many Artemisia and Achillea oils, contributing to aroma and to reported antioxidant/antimicrobial properties of the volatile fraction.

Rubefacient and mildly antiseptic terpenoids that underpin topical use of yarrow oils for aches and skin conditions; camphor is toxic if ingested in quantity.

Chemotype-defining constituents; their high proportion in certain populations illustrates the strong intraspecific variability of A. nobilis oil composition.

These flavones and their glycosides account for much of the antioxidant, anti-inflammatory and acetylcholinesterase-inhibitory activity reported for the aqueous and ethanolic extracts.

Potent radical scavengers contributing to the strong antioxidant capacity measured in DPPH/ABTS assays and to anti-inflammatory effects.

Impart the bitter tonic and antiparasitic character typical of the genus; sesquiterpene lactones are also the class most often responsible for allergic contact dermatitis from Asteraceae.

Traditionally, roughly 1–2 g of dried flowering tops is steeped in a cup of hot water for 5–10 minutes and taken for digestive complaints, flatulence, abdominal pain or as an emmenagogue in the folk medicine of Anatolia and the Balkans. Because the essential oil is rich in α-thujone (a neurotoxic GABA-A antagonist), prolonged or high-dose internal use is discouraged and the herb should be avoided in pregnancy and lactation.

A stronger decoction or the crushed fresh herb is applied topically to wounds, rashes, psoriasis and haemorrhoids in Balkan and Iranian folk practice. Patch-test first: the sesquiterpene lactones can provoke allergic contact dermatitis in Asteraceae-sensitive individuals.

The steam-distilled oil is used externally in dilution. Owing to high thujone and camphor content it is not recommended for internal consumption; ingestion risks neurotoxicity and seizures.

Achillea nobilis is among the medicinal plants contextualised within Traditional Kazakh Medicine described in this text; the species is still used in Kazakh folk practice for urethritis, bronchitis and psoriasis.

Dried flower heads used as a diuretic, emmenagogue and wound remedy, and against abdominal pain, flatulence and diarrhoea in Turkey; blood purification and dermatological use recorded in Bosnia-Herzegovina.