Pharmacognosy - medicinal plants (herbs)

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Theme VII: Analysis of extracts

Analysis of extracts

Extracts. Definition. Analysis of extracts. Production. Identification. Trials. Quantitative determination. Labelling.

To certify the quality of the extraction methods of medicinal plants should be subjected to a set of tests to verify through indicators and titrations that the product is suitable and meets the specifications that were expected.


The methods presented are general, for each product are described the specific tests.


The following trials and definitions were taken from:

British Pharmacopoeia Monographs Volume III Formulated Preparations: General Monographs EXTRACTS


Defining Extracts


The extracts are preparations of liquid consistency (fluid extracts and tinctures) or semisolid (soft or dense extracts), or solid (dry extracts); obtained from plant drugs or animal tissues on generally dry state.


There are different types of extracts. The adjusted extracts are within an acceptable tolerance of the content of constituents with known therapeutic activity.


Standardized extracts are achieved by adjusting the extract with inert substances or mixing batches of extracts.


Quantified extracts are adjusted to a defined range of constituents. The adjustments are made by mixing batches with the extract or adding specific material.


Other extracts are essentially defined by its production process (by the state of the plant drug or animal tissue to be extracted, by the solvent, by the extraction conditions) and its specifications.


The extracts are prepared with appropriate methods using ethanol or other suitable solvent. Different batches of drug plant or animal tissue can be mixed prior the extraction. The plant drug or animal tissue to be extracted must be subjected to a preliminary treatment, for example, enzyme inactivation, milling or grinding. Furthermore, undesirable materials must be removed before the extraction.


Plant drugs, animal tissues and organic solvents used for preparing extracts meet either of the pharmacopoeias. For dense and dry extracts wherein the organic solvent is eliminated by evaporation, can be used solvent recovered or recycled, provided that the recovery procedure is controlled and monitored so that the solvent meets the appropriate standards before reuse or mix with other accepted materials.


The water used for the preparation of extracts should have appropriate quality. Except for the bacterial endotoxin test, the water meets the purified water section of the monograph. Drinking water may be used if it meets the specification defined for the production of a certain extract.


If applicable, to achieve the concentration of the consistency there are methods such as reducing pressure at a temperature in which the deterioration of the components is minimized.


Essential oils that have been separated during the process can be replaced at a proper stage during the manufacturing process. The excipients used may be added conveniently at different stages of the manufacturing process for example, to improve the technological quality such as homogeneity or consistency. The stabilizers and antimicrobial preservatives may also be added.


The extraction with a given solvent leads to the typical proportions of a constituent characterized in the extractable material. However during the standardization and quantification process, can be applied purification procedures to increase such proportions with respect to the expected value, such extracts are referred as “refined”.

Extracts identification

Extracts are identified using the specified methods of each monograph.


Trials applicable to plant drugs or animal tissues are depending of the production process used: microbiological tests, heavy metals, toxins and pesticide residues.

Quantitative determination

Whenever possible, the extracts must be analyzed by specific methods.


Labeling of extracts

In the identification of a product obtained from a plant drug or animal tissue must be specified: If the extract is fluid, soft, dry or a tincture.


For the standardized extract: content of known active ingredients.


For quantified extracts: the content of constituents used for the quantification, the proportion of the starting material added to the original extract. The solvent or solvents used for extraction.


If applicable specify if the drug plant or animal tissue used is fresh. If applicable specify if the extract is refined. The name and amount of any excipient used including stabilizers and antimicrobial preservatives. If appropriate, specify the percentage of dry residue.

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Extracts. Definition. Analysis of extracts. Production. Identification. Trials. Quantitative determination. Labelling.