Extract

Extracts are concentrated preparations of liquid, dry or viscous nature, usually prepared from dried parts of plants (medicinal drugs) by maceration or perlocation. Drugs usually contain about 20% extractable substances, which corresponds to a drug/extract ratio (DEV) of 5:1.

In comparison to the previous extract framework monograph 0765 (1997), the European Pharmacopoeia proposes the following for the preparation: "that extracts should be prepared by suitable validated methods with the appropriate solvents". Methods of percolation and maceration are only described for the classical pharmaceutical form of tinctures.

Furthermore, the European Pharmacopoeia defines herbal extracts "as liquid, solid or semi-solid preparations of dried plant or animal material. Extracts may be subjected to purification and enrichment processes, in which case the extracts should be described as "enriched" or "purified"".

Purity tests: For this purpose, the European Pharmacopoeia prescribes tests for microbial purity and for contamination with heavy metals, mycotoxins, radioactivity and pesticides, unless risks can be excluded by other means.

Plant extracts can be assigned to certain categories:

Extract category type A . Extracts containing ingredients (individuals or groups) with a known and scientifically documented therapeutic activity that are solely responsible for the clinical efficacy of these extracts. A standardization of these extracts (normalization) to defined ingredients should be provided for. An example of this is standardised Senna extract.

Extract category of type B. Extracts with chemically defined ingredients (individual or groups) for which scientifically relevant pharmacological properties are known. These substances are believed to make significant contributions to clinical efficacy. However, there is usually no evidence that they are solely responsible for clinical efficacy; example: ginkgo extract or St. John's wort extract. Monographs for this type B extract should define important parameters of extract production as far as possible.

Extract category type C: Extracts for which no chemically defined substances can currently be identified as responsible for pharmacological or clinical efficiency. Alternatively, chemically defined ingredients (markers or lead substances) may be used for control purposes, even if they have not been shown to contribute to therapeutic activity. These marker or reference substances should be named to enable GMP-compliant manufacture; example: valerian or nettle root extract.

The composition of an extract is usually complex due to its manufacturing process. This also applies to phytopharmaceuticals not obtained by extraction. In spite of this complexity, the entire extract (according to AMG §3, para. 2) is by definition always referred to as "active ingredient".

As a rule, in a herbal extract there are efficacy determining ingredients to which those components are added to which the therapeutic properties of the native drug are wholly or predominantly bound.

Furthermore, an extract contains accompanying substances which are not worthless in terms of the reproducible overall effect but which can support the main effect. They can, for example, promote the absorption of certain active components or increase their stability (co-effectors).

Furthermore, an extract usually contains little defined matrix substances (varying according to the use of the solvent used), which are important as matrix formers of the extract.

Thus, a plant extract is always a multi-component mixture which in its complex composition has an effect on the organism. It is difficult to impossible to correlate pharmacological or clinical data obtained with an extract in vivo and in vitro qualitatively and quantitatively with the pharmacological or clinical data of individual components. Studies on the effect of individual ingredients in the various pharmacological models can only insufficiently answer the question whether exactly one particular ingredient is responsible for the particular clinical efficacy. In vivo data are generally considered to be more meaningful than in vitro data.

In addition to the efficacy determining or co-determining ingredients, undesirable components (toxins, allergens, etc.) may also be present in the concomitant substances and matrix substances, which can be removed from an extract by modifying an extraction procedure accordingly, e.g. by depletion.

Sequence extract types are distinguished:

• Liquid extracts (fluid extracts) are produced exclusively by using ethanol, water or mixtures of ethanol and water
• Dry extracts are solid preparations obtained by evaporation of the solvent used to prepare them (native dry extract).
• Essential oils which are generally obtained from the drug directly by distillation processes or, more rarely, via lipophilic extracts can be regarded as active substance concentrates. The drug extract ratio (DEV) of essential oils is about 50 - 100:1 (1-2% essential oil).

It is desirable to carry out the greatest possible standardisation of extracts on the market, at least for Europe. It is difficult to carry out a comparison (essential similarity) of the extracts currently available and the finished medicinal products manufactured from them or to postulate comparability.

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