Senna (herb)
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| Senna alexandrina Mill. |
Senna is the common name for many species in the genera Senna and Cassia, both in the family Fabaceae, subfamily Caesalpinioideae. The term "Senna" is often used specifically for the medicinal herb Senna alexandrina (syn. Cassia acutifolia).
Senna alexandrina is a small shrub, about 0.5-1 m high, with a pale green smooth erect stem, long spreading branches, bearing four or five pairs of leaves. The flowers are small and yellow, the pods broadly oblong and containing about six seeds.
Senna is an Arabian name, and the plant is grown mostly in Nubia. Twice a year the plants are cut down, dried in the sun, stripped and packed in palm-leaf bags and sent on camels to Essouan and Darao then up the Nile to Cairo or else to Red Sea ports.
It is a purgative, similar to aloe and rhubarb in having as active ingredients anthraquinone derivatives and their glucosides. Its action is on the lower bowel, and is especially useful in alleviating constipation. It increases the peristaltic movements of the colon.
The pods are milder in their effects than the seeds as they contain less of the resin responsible for griping.
Another species of senna, Cassia obovata, is used as a hair treatment with effects similar to henna, but without the red color. The active component is an anthraquinone derivative called chrysophanic acid, which is also found in higher concentrations in rhubarb root. It adds a slight yellow color. Cassia obovata is often called "neutral henna".
