Ask A Scientist© Biology Archive

Author:      Linda Martin
Text:        What exactly is the astringent that is found in persimmons that 
makes your mouth pucker?

Response #:  1 of 1
Author:      wizkid
Text:        The astringents in persimmons are tannins (tannic acid) and other 
polyphonously compounds.  There are many forms of tannins, but generally there 
are two groups:  1) flavonol derivatives and 2) esters of sugar, usually 
glucose, with one or more trihydroxybenzenecarboxylic acids.  Tannins can be 
found in many plants and trees, including oak, sumac, myrobalan, and the 
Chinese nutgall.  How do astringents work?  Basically, they reduce the 
permeability of cell membranes and hardens the cement substance of the 
capillary endothelium (the inner cell layer of capillaries).  In effect, this 
inhibits movement of plasma protein through capillaries, which thus reduces 
local edema (swelling) and inflammation.  Muscle contraction and tissue 
wrinkling accompanies the effect.  Since astringents do not penetrate very 
deeply into cells, the action is limited to the cell surface and interstitial 
(in-between cells) spaces.  The American Indians had many uses for persimmons 
(scientific name:  Diospyros virginiana L.).  The infusion of the fruit was 
used to treat diarrhea, dysentery, uterine hemorrhages, and sore throats.  The 
powdered seeds were mixed with water to make a drink for kidney stones.  The 
boiled bark was used for sores of the mouth, lips and throat.  A lot of good 
from a simple tree and its fruit!