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What do dry extracts mean?

Sep 15, 2020
Categories:  Scientific publication
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Author:  Vita Forest

Dry extracts are concentrated extracts obtained from medicinal plant raw materials. It looks like loose powders with a moisture content no more than 5%.

Dry extracts can be divided into:

  • extracts with a limited upper limit of active substances (standardized extracts). It is obtained from raw materials containing highly active biological compounds, therefore its content in the extract should be in a strictly defined amount. To do this, the dry plant extract is mixed with neutral materials (dextrin, lactose, glucose, etc.) or another extract containing more or less active ingredients.
  • extracts with an unlimited upper limit of active substances. It is obtained without adding carrier/excipients from medicinal raw materials containing non-potent substances.

There are two schemes for the production of dry extracts:

1. Extraction

2. Cleaning

3. Extract thickening

4. Drying of the thickened extract

1. Extraction

2. Cleaning

3. Drying of the liquid extract


Dry extracts are obtained by extraction. It is carried out by a special solvent suitable for specific plant materials. Water, alcohol of various concentrations, organic solvents can be used. Sometimes glycerin or some types of acids are added to the composition.

All existing extraction methods are classified into static and dynamic according to the process. In static methods, the raw material is periodically filled with an extractant and infused for a certain time. In dynamic methods, a constant change of extractant or raw materials and extractant is provided.

Due to the flow direction of the extractant and raw material, there are straight-flow (extractant and material in the same flow) and countercurrent (active movement towards each other of the extractant and plant material) extraction.

In order to prepare a high-quality extract, the following extraction techniques are used:

  1. Maceration and remaceration.
  2. Percolation.
  3. Repercolation.
  4. Countercurrent extraction.
  5. Different techniques, which include grinding raw materials inside the extractant, vortex extraction, the use of ultrasonic waves, pulsed magnetic field, electrical impulse exposure, and so on.

Water, as well as water-alcohol extracts, which have a small amount of ethanol (20-40%), contain a lot of high-molecular compounds (sugar, water-soluble proteins, etc.). It is very important to remove it from the extract before the evaporation process begins.

Depending on the quantity and properties of ballast substances, different cleaning methods must be used. In some situations, boiling can be used (if, under the influence of elevated temperatures, inactivation of biologically active substances does not occur). Proteins that coagulate during this treatment flake off very quickly. Sometimes adsorbents (bentonites, talc or kaolin) can be used, as well as its combination with subsequent boiling. An alcohol precipitation method is often used for ballast removal.

The resulting extracts are thickened. To do this, it is evaporated under vacuum to the required consistency. Depending on the production scheme, this stage may be skipped.

The drying of the liquid extract can be carried out in spray or sublimation (lyophilic, molecular) dryers. The slightly thickened extract is dried in a vacuum dryer.

Dry extracts contain all the biologically active substances inherent in this type of raw material. It is convenient to store and transport. The high concentration of dry substances allows you to use extracts in the finished form in a small amount. Dry extracts are convenient for use in the production of beverages, dietary supplements, medical cosmetics and other functional products (for example, veterinary medicine or sports nutrition).