# Senna (Senna alexandrina)

**Sena**

**Known today as.** The leaves and pods of *Senna alexandrina*.

Kind: Plant

## What did Canale use it for?

Infused or powdered, in nearly every purge for every complexion; “choice” senna is specified (chs. 2, 4).

## What does modern science say?

Confirmed. Senna’s sennosides are among the most reliable stimulant laxatives and remain in pharmacies today. Its sennosides are converted by the bacteria of the colon into compounds that stimulate the bowel wall some six to twelve hours after a dose, which is why it was given at night. It is on the World Health Organization’s list of essential medicines; long daily use stains the lining of the colon brown (melanosis coli), which is harmless, and can cause dependence.

## Pharmacognosy and toxicology

- **sennoside A**: 
- **sennoside B**: 

**Mechanism.** Gut bacteria free the anthrone, which stimulates the nerves of the colon and holds water in it.

**Dose.** Overdose brings cramps and dehydration; chronic use, dependence and a brown colon.

**Standing.** On the WHO list of essential medicines as a laxative.

## What lore surrounds it?

Mecca senna, Tinnevelly senna, and Alexandrian senna were long argued over in the trade, the Alexandrian leaf fetching the most; the pods, milder than the leaves, were steeped overnight as “senna tea.”

## What did the older authorities say?

**The Arab physicians.** Brought senna into the pharmacopoeia in the ninth century: Serapion and Mesue prescribe it, and the Alexandrian leaf, shipped from Nubia and the Sudan through Alexandria, gave the plant its Latin name and its reputation as the gentlest of the strong purges.

**The Salernitan school.** Took it up from the Arabs, and by the fourteenth century senna stood in nearly every European purge for every complexion, usually corrected with ginger, aniseed, or raisins against its griping.

## Sources

- Mesue, *De simplicibus*.
- World Health Organization, *Model List of Essential Medicines*.
- World Health Organization, *Model List of Essential Medicines*.

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

Historical description, not medical advice.