[The influence of extraction method on the quality of the liquid extract of St John's wort].

: The liquid extract of St John's wort was produced by methods of remaceration, percolation, and repercolation. Extraction by remaceration did not result in the complete extraction of herbal raw material; therefore, this method was rejected. Extraction by percolation requires the process of evaporation of the weak extract to take place, during which the active substances can decompose. This method was found to be not efficient. The liquid extract of St John's wort was produced by the complete-cycle repercolation: by dividing the raw material into unequal parts, and by dividing it into equal parts. It has been found that the highest concentration of hypericine, flavonoids and the dry remainder is obtained in the extract produced by repercolation with raw material divided into equal parts. The optimal method of extraction for St John's wort has been confirmed to be the complete-cycle repercolation with raw material divided into equal parts. In the course of the experiment, it was observed that the release of active substances from the raw material is influenced by the density of raw material filling. The optimal density of raw material filling has been found to be 0.11 g/cm3. The most suitable usage period was found to be 2 years.