Achillea collina

Deep-blue sesquiterpene formed during steam distillation from the guaianolide proazulene matricin. The presence of chamazulene marks the tetraploid A. collina as a proazulene-rich chemotype of the yarrow aggregate; it is credited with anti-inflammatory and antioxidant activity and gives the oil its characteristic colour.

A major monoterpene of the oil; its abundance alongside chamazulene is regarded as a chemotaxonomic signature of the tetraploid form. Contributes to the oil's aroma and to reported antibacterial and mild anti-inflammatory effects.

A widespread sesquiterpene and dietary cannabinoid (CB2) ligand associated with anti-inflammatory and analgesic activity; a consistent major component of A. collina oil.

Oxygenated monoterpene with documented antimicrobial, mucolytic and anti-inflammatory properties; a prominent oxygenated component of the oil.

Bitter guaianolide lactones (matricin-type) are the precursors of chamazulene and underlie the plant's classification as a proazulene chemotype. They contribute anti-inflammatory and spasmolytic activity but are also the sesquiterpene-lactone allergens responsible for Asteraceae contact dermatitis.

Like other members of the A. millefolium aggregate, the aerial parts contain caffeoylquinic acids and flavonoids (apigenin/luteolin glycosides) that account for much of the strong DPPH radical-scavenging and lipid-peroxidation-inhibiting antioxidant activity measured for the extracts.

As with common yarrow, 1-2 g of dried flowering herb is steeped in ~150 mL hot water for 10-15 minutes and taken as a bitter digestive/diaphoretic tea. People allergic to Asteraceae (ragweed, chamomile, chrysanthemum) may react to the sesquiterpene lactones and should avoid it.

Steam distillation yields a blue, chamazulene-rich oil used topically (well diluted) for its anti-inflammatory reputation. The tetraploid chamazulene chemotype is preferred for this purpose; the oil is for external or aromatherapeutic use, not undiluted internal use.