Fabaceae
Senna alexandrina
Senna · Alexandrian senna · Sanay
- Part used
- leaffruit
- Native range
- The Nile valley, the Arabian peninsula and India
- Morphology
- A small shrubby legume to a metre with pinnate leaves of narrow leaflets, yellow flowers and flat papery pods.
- Also known as
- Cassia senna, Cassia angustifolia
What is in it
Evidence
Unambiguously effective as a stimulant laxative and a registered over-the-counter medicine worldwide. The sennosides are hydrolysed by gut bacteria into the active form, which acts directly on the colon.
Safety
Effective and easily misused. Prolonged use causes electrolyte disturbance, particularly potassium loss, and dependence in the sense that bowel function becomes reliant on it. Chronic use produces melanosis coli, a harmless pigmentation used clinically as a marker that someone has been taking laxatives. Heavily misused in eating disorders, and in weight-loss teas where it is often the undeclared active ingredient.
Interactions: Potassium loss compounds digoxin toxicity and diuretics; Reduces absorption of other oral drugs
Regulatory: A registered over-the-counter medicine. Permitted as a food ingredient in some contexts, which is how it ends up in slimming teas.
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
Introduced to European medicine by Arabic physicians around the ninth century — one of the clearest cases of the Islamic tradition adding a genuinely new and effective drug to the inherited Greek pharmacopoeia rather than merely preserving it.
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
Senna is one of the very few unambiguous successes in this collection: it works, it is a registered medicine, and nobody disputes it.
It is also the answer to anyone who thinks Arabic medicine merely preserved Greek learning. Senna is not in Dioscorides. It entered European practice around the ninth century through Arabic physicians who had added it from their own materia medica — a genuinely new and effective drug contributed to a tradition that is usually described as having been handed down intact.
Its modern problem is misuse rather than efficacy. It is the most common undeclared active in weight-loss and "detox" teas, where the dramatic result people report is a stimulant laxative doing exactly what it does, and it is heavily used in eating disorders. A drug that works can be misused precisely because it works.
Nomenclature verified against GBIF backbone taxonomy.