# Chaste tree (Vitex agnus-castus)

**Agnus castus*, *vitex*; monk’s pepper*

**Known today as.** *Vitex agnus-castus*, a Mediterranean shrub with spikes of lilac flowers and peppery fruit.

Kind: Plant

## What was it used for?

To cool desire, as its names say; for the womb and to bring on the milk.

## What does modern science say?

One of the few old women’s herbs with trial support: extracts of the fruit have eased premenstrual symptoms in controlled studies, likely by acting on prolactin.

## Pharmacognosy and toxicology

- **agnuside**: 
- **casticin**: 
- **rotundifuran**: 

**Mechanism.** Extracts bind dopamine D2 receptors in the pituitary and so lower prolactin, the likeliest basis of the effect on the premenstrual syndrome.

**Dose.** No serious harm; headache and nausea in a few.

**Standing.** A German trial in 2001 found it better than placebo for premenstrual symptoms; approved in Germany for that use.

## What lore surrounds it?

The peppery fruit was said to be eaten in monasteries to keep vows of chastity, hence monk’s pepper.

## What did the older authorities say?

**Pliny.** Reports that the women of Athens, keeping chaste for the festival of the Thesmophoria, strewed their beds with its leaves.

**Dioscorides.** Gives the seed to take away the desire for coition.

## Sources

- Pliny the Elder, *Natural History*.
- Dioscorides, *De materia medica*.
- Schellenberg, R. (2001). “Treatment for the premenstrual syndrome with agnus castus fruit extract.” *BMJ* 322.
- Schellenberg, R. (2001). *BMJ* 322.
- Wuttke, W., et al. (2003). “Chaste tree (*Vitex agnus-castus*): pharmacology and clinical indications.” *Phytomedicine* 10.

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*Chaste tree.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-09-30. The Thinking Press. https://thethinkingpress.org/materia-medica/chaste-tree

Historical description, not medical advice.