Interactions between aqueous Hypericum perforatum extracts and drugs: in vitro studies

Physico-chemical interactions between drugs and plant extracts can result in the formation of nanoparticles, microparticles and precipitates. The extraction method may have an influence on the components of the plant preparations and the interactions between drugs and plant extracts. In this study the particle formation in different drug-containing preparations of Hypericum perforatum L. was compared. The formation of nanoparticles was investigated by PCS and scanning electron microscopy. Precipitates were separated from nanoparticles by centrifugation or filtration. The particle formation in drug-containing infusions and reconstituted methanolic extracts of Hypericum perforatum L. was different. In reconstituted dry extracts 21.5% 17alpha-ethinylestradiol and 36.6% levonorgestrel was bound to precipitates, in aqueous Hypericum infusions less than 4% of the hormones was bound. In infusions containing desipramine nanoparticles were formed while the formation of nanoparticles in desipramine-containing reconstituted extracts was negligible. Up to 10% of desipramine was bound to precipitates in reconstituted extracts, but only 4% was associated with the precipitate of infusions. The interactions between extracts of Hypericum perforatum L. and drugs depended on the extraction method. Reconstituted methanolic extracts showed a more intensive binding with oral contraceptives than aqueous infusions.