Mesembryanthemum tortuosum

Mesembryanthemum tortuosum (many synonyms, including Sceletium tortuosum) is a succulent plant in the family Aizoaceae native to the Cape Provinces of South Africa. It is known as kanna, channa, kougoed (kauwgoed/ 'kougoed', prepared from 'fermenting' M. tortuosum )—which literally means, 'chew(able) things' or 'something to chew'.

Eight species related to M. tortuosum have also been placed in the genus Sceletium: M. crassicaule, M. emarcidum, M. exalatum, M. expansum, M. archeri (S. rigidum), M. ladismithiense (S. strictum), M. tortuosum and M. varians.

History
The plant has been used by South African pastoralists and hunter-gatherers as a mood-altering substance from prehistoric times. The first known written account of the plant's use was in 1662 by Jan van Riebeeck. The traditionally prepared dried plant was often chewed and the saliva swallowed, but it has also been made into gel caps, teas and tinctures. It has also been used as a snuff and smoked.

Uses
M. tortuosum is traditionally used to fight stress and depression, relieve pain and alleviate hunger.

M. tortuosum has been studied to alleviate excessive nocturnal barking in dogs, or meowing in cats, in pets diagnosed with dementia.

Cultivation
M. tortuosum can be grown from seeds and be propagated from cuttings. Its cultivation and care are similar to cactaceae like Echinopsis. The optimal temperature is at least 16°C and it does not tolerate frost.

Pharmacology
M. tortuosum contains about 1–1.5% total alkaloids. A standardised ethanolic extract of dried M. tortuosum had an IC50 for SERT of 4.3 μg/ml and for PDE4 inhibition of 8.5 μg/ml.

Mesembrine
Mesembrine is a major alkaloid present in M. tortuosum. There is about 0.3% mesembrine in the roots and 0.86% in the leaves, stems, and flowers of the plant.

General
Traditional and contemporary methods of preparation serve to reduce levels of potentially harmful oxalates found in M. tortuosum. An analysis indicated levels of 3.6–5.1% oxalate, which falls within the median range for crop plants, just like spinach or kale. It is speculated that physical crushing of the plant and the fermentation process reduce the potentially harmful effects of oxalic acid. In particular, free oxalic acid is likely to complex with cell wall-associated calcium salts and precipitate as calcium oxalate when plant material is crushed.

Human studies
In a study evaluating its safety, a 2:1 standardised extract consumed by healthy adults at a dose of up to 25 mg once daily over a three-month period was well tolerated, with adverse effects such as headache not occurring more than when taking a placebo.