# Goat’s rue (Galega officinalis)

**Ruta capraria*; *galega**

**Known today as.** *Galega officinalis*, French lilac.

Kind: Plant  
Toxic: yes

> **Caution.** 

## What did Canale use it for?

Seed in a powder for the bewitched; flowers in a conserve; juice in the oil; among the amulets (chs. 6, 9, 10).

## What does modern science say?

Here the old herbalists hit on something real: goat’s rue is rich in guanidine compounds such as galegine, which lower blood sugar, and the modern diabetes drug metformin descends from this line of research. Its folk reputation was against plague and fevers, and to increase milk.

## Pharmacognosy and toxicology

- **galegine**: a guanidine

**Mechanism.** Galegine lowers blood sugar and was too toxic to use; the biguanides made from it in the 1920s gave, after Jean Sterne’s trials in 1957, metformin, the most prescribed drug for diabetes in the world.

**Dose.** The plant has killed sheep; galegine in the clinic was abandoned for its toxicity.

**Standing.** Metformin is on the WHO list of essential medicines; the herb is not used.

## What lore surrounds it?

Its folk use against the plague was widespread enough in medieval Europe to survive into the modern record, beside its uses for worms and snakebite and to increase milk. The road from folklore to pharmacy is unusually direct here: galegine, the blood-sugar-lowering compound the herbalists were unknowingly using, led researchers to the biguanide drugs, of which metformin is still prescribed today.

## Sources

- Wikipedia, “*Galega officinalis*.”
- Bailey, C. J., and Day, C. (2004). “Metformin: its botanical background.” *Practical Diabetes International* 21.
- Sterne, J. (1957). “Du nouveau dans les antidiabétiques: la NN diméthylamine guanyl guanidine.” *Maroc Médical* 36.

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*Goat’s rue.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-09-25. The Thinking Press. https://thethinkingpress.org/materia-medica/goats-rue

Historical description, not medical advice.