Extraction of Ginkgo biloba L. by carbon(IV)-oxide under pressure. [Doctoral dissertation] | Ekstrakcija ginka (Ginkgo biloba L.) ugljenik(IV)-oksidom pod pritiskom. Doktorska disertacija

Within this thesis preparative isolation of essential oil from leaves of ginkgo (Ginkgo biloba L.) by hydrodistillation was carried out, in order to determine some physico-chemicals parameters. The essential oil content in the leaves of ginkgo was determined by an officinal procedure and its value is 0.0083%. Ginkgo leaves were extracted with conventional solvents, i.e. alcohol-water mixture, were the alcohol concentration was 40% (w/w). The forementioned solvent was used to carry out a multi-stage counter-current extraction (five stages) by which the liquid extract (Extracta fluida) with a relatively high content of extractive matter (17.06%) was obtained. The liquid extract was directly used to obtain a dry extract of ginkgo leaves (Extracta sicca) by spay drying. The qualitative and quantitative characterization was based on the proceedings of thin layer chromatography (HPTLC). The content of total flavonoids expressed as rutin, as well as (+)-catechin, and the total phenol content expressed as chlorogenic and gallic acid, determined. The main part of the doctoral thesis is investigation of the extraction system of ginkgo leaves – carbon(IV)-oxide under pressure, in which the effect of the drug particle size on the extraction yield was studied, and as a measure of the kinetic behavior of extraction system the coefficient of fast and slow extraction was used. The obtained results showed a significant effect of the drug particle size on the rate of extraction, particularly, the extraction with supercritical carbon (IV)-oxide. In order to find the most favorable conditions of extraction, the response surface methodology by varying of extraction parameters (pressure, temperature and extraction time) was used. Based on the experimental results, a second order polynom for the calculation of the optimum yield of extraction was obtained, and the extraction conditions and the mutual influence of some parameters were determined.