SUMMARY
For the first time quantitative effects of liquefied gas extraction temperature, the correlation of the extractant volume and the raw material mass, humidity and the average size of the raw material particles have been analyzed in the lipophilic complex (LC) yield from the overground part of yellow bedstraw (Galium verum L.) using the response surface methodology (RSM). For this research, the four-factor and the three-level Box-Behnken design has been chosen; it contains four covariates, namely the extraction temperature – X1, the ratio of the extractant volume (ml) and the raw material mass (g) – X2, the raw material humidity – X3 and the average size of the raw material particles – X4 based on the results of one-factor test. Twenty seven experimental studies have been conducted with three repeats in the centre of the design to assess the proper operational margin of the sum of squares. The experimental results obtained have been set at the polynomial equations of the second order using the multiple regression analysis, and analyzed by the corresponding statistical methods. With the help of solving the regression equation and by means of the analysis of the response surface of contour plots the optimal conditions of the LC extraction have been determined: the extraction temperature – 35°C, the ratio of the extractant volume (ml) and the raw material mass (g) – 8, the raw material humidity – 7% and the average size of the raw material particles – 1 mm. It has been found that the most significant factors for the process under research are the extraction temperature, the ratio of the extractant volume (ml) and the raw material mass (g), and the raw material humidity. Comparison of the data obtained with the data of literature sources confirms the relevance of the subcritical difluorochloromethane choice as an extractant for the LC obtaining. Summarizing all above-mentioned information it may be concluded that the use of liquefied difluorochloromethane for the LC extraction from the overground part of yellow bedstraw (Galium verum L.) is promising from the viewpoint of the modern pharmaceutical technology, and the use of the RSM as an instrument for the process optimization allows reducing the costs for carrying out the pharmaceutical development.