The principal anthraquinones are found in Rhamnus frangula and R. purshiana, Aloe ferox, A. barbadensis, A. succotrina, A. vera and A. africana. Rheum palmatum and R. officinale, Cassia acutifolia and C. angustifolia. The common name for the last group is Indian or African senna; these plants contain sennosides with anthranoid structures like those found in the Rhamnus and Aloe plants. The anthraquinones usually occur in nature as glycoside derivatives of anthracene. The glycosides behave like pro-drugs, liberating the aglycone that acts as the laxative. Figures 7 and 8 show the principal glycoside forms of natural anthraquinones and their metabolism to the active aglycones. The metabolism takes place in the colon (Fig. 9), where bacterial glycosidases remove D-glucose or L-rhamnose (Longo 1980; Hattori et al. 1982; Dreessen and Lemli 1988). Germ-free animals do not have a laxative response to orally administered anthraquinones. The products obtained are poorly absorbed and act by evoking secretory and motility changes in the colon (Hardcastle and Wilkins 1970; Garcia-Villar et al. 1980; Leng-Peschlow 1980; Beubler and Kollar 1985; Leng-Peschlow 1986; Frexinos et al. 1989; de Witte et al. 1991). The effect on secretion is probably the consequence of exaggerated intestinal production of prostaglandins and of other autacoids (Beubler and Juan 1979; Capasso et al. 1986; Autore et al. 1990a, 1990b; Nijs et al. 1991).
KeywordsAlginic Acid Ricinoleic Acid Botanical Origin Laxative Effect Laxative Action
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