Intensification of ultrasounic extraction of active compounds from Hypericum perforatum using bio-solvents

Intensification of ultrasounic extraction of active compounds from Hypericum perforatum using bio-solvents

Oral presentation

Maria Boykova, Ilonka Saykova
Department of Chemical Engineering, University of Chemical Technology and Metallurgy, Sofia, Bulgaria

The objective of this study is to determine the optimum conditions for obtaining Hypericum perforatum extracts, which are enriched in hypericins, characteristic condensed anthraquinones, involved in several biological activities of this medicinal plant. The improvement of a process for obtaining extracts commonly in therapeutic use (according to the European pharmacopeia, standardized to containing at least 0.3% hypericines, 6% flavonoids, and maximum 6% hyperforin) is justified by a small and variable amount of hypericins, low solubility and lack of stability in solution under light and oxygen. Experiments are conducted in an ultrasounic bath with input power of 100 W at a frequency of 36 kHz. The solvents used were water, ethanol/water (10-96%), and glycerol-water mixtures (10-89%).The extracts are characterized by the total yield, the content of hypericins, flavonoids and phenolics, and the antioxidant activity. Parameters such as mechanical agitation (300-1000 rpm), temperature (20-80°C), solvent-to-solid ratio (0.01-0.06 m3/кg), and duration of treatment, with and without ultrasound, are evaluated. The experiments demonstrated that the influence of solvent on the efficiency of ultrasound irradiation is related to the variation of the acoustic power density (20.4-35.7 W/l), mainly associated with the dissimilar acoustic impendance and viscosity of a liquid. Ultrasonication alone could be not effective because of the insufficient mixing and homogenization under concentrated dispersions. However, the combination with moderate agitation and heating is an effective approach for better controlling cavitation intensity, and leading to substantial shortening of extraction time, higher yields and purity of active compounds.
Keywords: Hypericum perforatum, bio-solvents, glycerol, hypericin, ultrasound