Achillea millefolium L. (Asteraceae)
Achillea, Milfoil, Nosebleed.
Achillea collina Becker and Achillea lanulosa Nutt. are closely related and are also frequently used.
Yarrow (British Ph 2009, European Ph, 6th ed., 2008 and Supplements 6.1, 6.2, 6.3 and 6.4).
Yarrow contains a volatile oil composed of various monoterpenes (including limonene and alpha-thujone), and sesquiterpene lactones (including achillicin, achillin, millefin and millefolide). Azulene is the major component in the closely related Achillea collina and Achillea lanulosa but it is reported to be absent in Achillea millefolium. Yarrow also contains pyrrolidine and pyridine alkaloids, flavonoids (including apigenin, quercetin and rutin), tannins and sugars.
Use and indications
Yarrow has been used in the treatment of bruises, swellings and strains, and for fevers and colds. It has also been used for essential hypertension, amenorrhoea, dysentery, diarrhea and specifically for thrombotic conditions. There is little, if any, clinical evidence to support these uses, but extracts and many of the constituents have reported anti-inflammatory and antiplatelet activity.
An in vitro study suggests that ethanol extracts of yarrow leaves and flowers markedly inhibit the cytochrome P450 isoenzyme CYP2C19 but have only weak inhibitory effects on CYP3A4. The clinical significance of the effects on CYP2C19 is unknown. For information on the pharmacokinetics of individual flavonoids present in yarrow, see under flavonoids.