Pharmacognosy - medicinal plants (herbs)

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Theme VI: Extraction methods

Extraction methods

To achieve a suitable concentration of the active ingredients contained in the plants and that their action can be more effective, it is necessary to perform several procedures through which are extracted the active ingredients with the adequate solvents, selected according to the solubility and stability of the beneficial substances.


Extraction methods allow to obtain products in pharmaceutical forms suitable for oral or external dosage according to the place of action recommended.


These preparations are known as: decoctions, infusions, fluid extracts, dense or dry (according to their content of liquids) and tinctures.


They are also known as galenic formulations, in honor to Claudius Galen the precursor of preparing drugs from plants.


From these procedures have been developed extractive techniques that allow to obtain active ingredients in pure form for more sophisticated medications processing: in the form of pills, liquids, ointments, capsules, etc., but they have failed to displace the original preparations which have become more booming at present, because of being more innocuous and the lower unwanted reactions.


Pharmacopoeias have included within its specifications regulations scientifically based to ensure the quality of these preparations, which do not require an accurate control as the official drugs, although some care must be taken in terms of preservation and storage time.


Immediate use is preferred because of its ease of preparation and be available at any time from the medicinal plant.


Prior to extraction treatment the plant must be cleaned carefully to avoid contamination with other plants or foreign mechanical particles. The aim is the extraction of substances using an appropriate solvent called menstruum solvent.


These extractions are distinguished from real solutions in which suspended substances are present.

The main extraction methods are:

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