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Interactions between aqueous Hypericum perforatum extracts and drugs: in vitro studies
R S Müller1, J Breitkreutz, R Gröning
1Department of Pharmaceutical Technology and Biopharmaceutics, Westfälische Wilhelms-Universität, Corrensstr. 1, 48149 Münster, Germany. rsmuller@uni-muenster.de
Phytotherapy Research : PTR
|March 3, 2005
Summary
The extraction method significantly impacts drug-plant interactions. Aqueous Hypericum infusions minimize drug precipitation compared to methanolic extracts, affecting nanoparticle formation and drug binding.
Area of Science:
- Pharmacognosy
- Pharmaceutical Chemistry
- Materials Science
Background:
- Physico-chemical interactions between drugs and plant extracts can lead to particle formation (nanoparticles, microparticles, precipitates).
- The extraction method influences the composition of plant preparations and subsequent drug-extract interactions.
- Hypericum perforatum L. (St. John's Wort) is a widely used medicinal plant, and understanding its interactions with co-administered drugs is crucial for patient safety and efficacy.
Purpose of the Study:
- To compare particle formation in different drug-containing preparations of Hypericum perforatum L.
- To investigate the influence of extraction methods (aqueous infusion vs. reconstituted methanolic extract) on drug-particle interactions.
- To quantify the binding of specific drugs (ethinylestradiol, levonorgestrel, desipramine) to precipitates and nanoparticles.
Main Methods:
- Particle formation was assessed using Photon Correlation Spectroscopy (PCS) and scanning electron microscopy.
- Precipitates were separated from nanoparticles via centrifugation or filtration.
- Quantification of drug binding to precipitates was performed for aqueous infusions and reconstituted methanolic extracts of Hypericum perforatum L.
Main Results:
- Reconstituted methanolic extracts showed significantly higher drug binding to precipitates: 21.5% ethinylestradiol and 36.6% levonorgestrel, compared to <4% in aqueous infusions.
- Aqueous Hypericum infusions containing desipramine led to nanoparticle formation, whereas reconstituted extracts showed negligible nanoparticle formation.
- Desipramine binding to precipitates was higher in reconstituted extracts (up to 10%) than in infusions (4%).
Conclusions:
- The extraction method critically influences the physico-chemical interactions between Hypericum perforatum L. extracts and drugs.
- Reconstituted methanolic extracts exhibit more pronounced binding of oral contraceptives compared to aqueous infusions.
- Aqueous infusions may offer a safer formulation approach by reducing drug precipitation and promoting nanoparticle formation for certain drugs like desipramine.