11. Ethnomedicinal plants popularly used in Thailand as laxative drugs

Laxative drugs are usually organized according to their mode of action, i.e. bulk forming agents, stool softeners, lubricants, saline laxatives, stimulants including some combined formulations. Among them, bulk forming laxatives promote the mildest laxation. The popular bulk forming herbal laxatives in Thailand and Southeast Asian countries are dry fruits of hairy basil (Ocimum americanum) and Scaphium scaphigerum both of which contain high amounts of mucilage substances. Ripe fruits of banana and papaya which contain pectin, and the rhizome of Amorphophallus spp. containing high amounts of glucomannan polysaccharides, are also popularly used as bulk laxatives. Several plants containing anthraquinone glycosides, i.e. leaves and pods of Senna (Cassia angustifolia), pods of C. fistula, young leaves and flowers of Senna siamea, leaves and seeds of S. tora have been used for stimulant laxatives. The leaves of Senna alata, listed in the List of Herbal Medicinal Product of Thailand A.D. 2006, are recommended as a herbal laxative drug showing astringent properties, attributed to the presence of both anthraquinones and tannins as active components. Correspondence/Reprint request: Dr. Wandee Gritsanapan, Department of Pharmacognosy, Faculty of Pharmacy, Mahidol University, Bangkok, Thailand. E-mail: [email protected] Wandee Gritsanapan 296 Castor oil, containing high content of ricinoleic acid, is a safe and effective herbal drug for treating constipation. Moreover, pulp from the ripe fruits of tamarind, which contains several organic acids, also promotes mild laxative action. Although these plants have been used as laxatives since ancient days, some of them have not been evaluated in terms of modern pharmacological techniques and also needed to be validated with appropriate clinical studies. Besides being consumed as drug preparations, the described laxative plants can also be consumed in forms of foods and drinks.