Page 240 - Pharmacognosy 2 PG303

Pharmacognosy-2 (PG303) Level 2 Clinical Pharmacy-Pharm D

on which they are based. Ca. 60-80% of the mixture comprises anthraquinone
glycosides (of the 5 aglycones emodin, aloe-emodin, rhein, chrysophanol, and
physcion) and ca. 10-25 % dianthrone glycosides; minor cytotoxic anthraquinone
glycosides (pulmatin, 1,8-dihydoxy-3-methyl anthraquinone-l-O-B-D-glucoside)
and the congeners chrysophanein and physcionin. Chromone glycosides, including
aloesone. Ca 1% stilbene glucosides and rhaponticin (3,5-dehydroxy- and 3,5,3’-
trihydroxy-4'-methoxy stilbene-3-B-D-glucoside, respectively). Ca 5-10%
tannins, a mixture of gallotannins and related compounds (galloyl-, hydroxy-
cinnamoyl- (p-coumaroyl-), galloyl-dehydro-cinnamoyl-glucoses, galloyl-
sucroses,.. etc.). Ca. 2-3% favonoids as rutin.

Uses
Because of its content of anthracene derivatives and tannins, depending

on the dose, it is used as a laxative (1-2 gm) or as astringent and stomachic
(0.1-0.2 gm). An example of intersecting dose-response curves; however, the
drug is used mainly as a laxative, for constipation, when hemorrhoids or anal
injuries are present and after rectal operations.

The mechanism of action: owing to the anthracene derivatives, as a
powerful colonic laxative, aloe emodin anthrone, the presumed active substance,
is formed in the colon by enzymic or bacterial reductive cleavage of the
anthracene derivatives. The anthrones irritate the mucous membrane, leading to
an increase in the secretion of mucous, thus stimulating peristalsis. At the same
time, the reabsorption of water and electrolytes is inhibited. The mechanism of
action of anthraquinones-containing laxatives is such that chronic use often upsets
the electrolyte balance. In particular, there is loss of K and, at the same time, Na
ions are removed through the loss of water. The K depletion finally leads to
paralysis of the intestinal musculature and the laxative becomes less active.

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