Lamiaceae
Vitex agnus-castus
Chaste tree · Chasteberry · Monk’s pepper
- Part used
- fruit
- Native range
- The Mediterranean and western Asia
- Morphology
- A deciduous aromatic shrub to five metres with palmate leaves of narrow leaflets and slender spikes of small lilac flowers, followed by peppercorn-like fruit.
What is in it
Evidence
Among the better-supported herbs for a specific indication. Several randomised trials and meta-analyses support it for premenstrual syndrome and for cyclical mastalgia, and it is used clinically in Germany. Evidence in infertility and menopause is weak.
Safety
Generally well tolerated. Acts on dopamine receptors and lowers prolactin, which is a real endocrine effect. Contraindicated with dopamine antagonists and dopamine agonists, and in pregnancy. May reduce the effectiveness of hormonal contraception.
Interactions: Opposes dopamine antagonists including antipsychotics and metoclopramide; Interacts with dopamine agonists such as bromocriptine; May reduce hormonal contraceptive efficacy
Regulatory: Permitted as a listed medicine ingredient in Australia.
How the traditions classify it
Three systems, rating the same plant. Where they disagree, none of them is correcting the others — they are separate frameworks that arrived at their categories independently.
Historical use
Used since antiquity for gynaecological complaints and, on the strength of the anaphrodisiac reputation, in monastic settings. The modern use for premenstrual symptoms is twentieth-century German.
Recorded as history and attributed where possible. Long use establishes that a plant was widely used, not that it worked, and not that it was safe.
Worth knowing
Chaste tree is one of the few plants in this collection with a genuine, characterised endocrine mechanism: its diterpenes act as dopamine D2 agonists on the pituitary, which lowers prolactin. That is a real hormonal action, it explains the premenstrual and mastalgia results, and it is the reason the interaction list is more serious than a herb for period pain would suggest.
The naming is also unusually revealing. Agnus castus means chaste lamb; monk's pepper says the same thing; the English chaste tree says it a third time. Three names in three languages all recording an anaphrodisiac reputation from Dioscorides, for a plant now sold almost exclusively for the opposite end of the reproductive system.
Nomenclature verified against GBIF backbone taxonomy.