Pharmacognosy - medicinal plants (herbs)
Pharmacognosy - medicinal plants (herbs)

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Theme V: Drug analysis methods

Drugs analysis methods

Determination of tannins in herbal drugs

For the determination of tannins in herbal drugs or dry extract, add 150 ml of water to a set amount of powdered drug or to the extract, in a round bottom flask of 250 ml.
Warm up on a steam bath for 30 min. Cool off under running water and transfer quantitatively the contents to a 250 ml volumetric flask. Rinse the round bottom flask and collect the rinse water in the volumetric flask, then dilute to 250 ml with water.


Leave the solid to settle and then filter with paper of 125 mm of diameter. Discard the first 50 ml of the filtrated. In case of a fluid extract or a tincture, dilute the set amount to 250 ml with water. Filter the mixture through a filter paper of 125 mm of diameter. Discard the first 50 ml of filtrate. Note: Perform all extractions and dilutions protected from light.


Total polyphenols


Dilute 5 ml of filtrate to 25 ml with water. Mix 2 ml of this solution with 1 ml of reagent phosphomolybdic-acid and 10 ml of water and dilute to 25 ml with a solution of sodium carbonate to 29%. After 30 min measure the absorbance using water as a blank.

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