# Walnut, middle bark of (Juglans regia)

**Scorza mezzana della noce**

**Known today as.** The inner bark of *Juglans regia*.

Kind: Plant

## What did Canale use it for?

Powdered, a dram at a time, as a vomit (ch. 5).

## What does modern science say?

Walnut bark is purgative, with a bitter, astringent taste. Juglone, the quinone that stains the hands and kills the plants beneath the tree, is a strong irritant and purgative; a dram of the bark powder would act as Canale says, and would not be given now.

## Pharmacognosy and toxicology

- **juglone**: 5-hydroxy-1,4-naphthoquinone, in the green husk, leaf, and inner bark
- **tannins**: 
- **ellagic acid**: 

**Mechanism.** Juglone is a reactive quinone that irritates the gut, which is Canale’s vomit at a dram of the bark, and is antifungal and allelopathic, poisoning the plants under a walnut tree. The leaf’s tannins are the astringent of the leaf tea.

**Dose.** The bark at Canale’s dram nauseates; the leaf tea is safe; juglone stains the skin and sensitises.

**Standing.** Walnut leaf has an EMA monograph (2014) for minor skin inflammation and sweating of the hands and feet; the bark has none.

## What lore surrounds it?

The walnut tree, *Juglans*, is Jove’s nut; the witches of Benevento were said to gather under a great walnut, and the tree’s poisonous shade is an old Italian belief that modern botany explains by the juglone its roots exude.

## What did the older authorities say?

**Dioscorides.** Gives the green rind and the leaves of the walnut as astringent, and the Latin herbals the inner bark, boiled, as a purge and a vomit, “the middle bark” being that between the outer rind and the wood.

**Pliny.** Says the walnut was brought from Persia by the kings, and that its shade and its smell are heavy and hurt the head, whence its ill name among the old.

## Sources

- Pliny, *Natural History* XV–XVII.
- Dioscorides, *De materia medica* I.
- EMA/HMPC (2014). *Community herbal monograph on Juglans regia L., folium* (EMA/HMPC/346737/2011).
- Strugstad, M. P., and Despotovski, S. (2012). “A summary of extraction, synthesis, properties, and potential uses of juglone.” *Journal of Ecosystems and Management* 13.

---

*Walnut, middle bark of.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-10-01. The Thinking Press. https://thethinkingpress.org/materia-medica/walnut-middle-bark-of

Historical description, not medical advice.