Nanoparticles in plant extracts: influence of drugs on the formation of nanoparticles and precipitates in black tea infusions.

The influence of the neuroleptics fluphenazine and promethazine on the formation of nanoparticles in aqueous tea infusions was investigated using photon correlation spectroscopy. Formation of nanoparticles and of precipitates was observed in decaffeinated tea and caffeine-containing tea. The amount of drug in the nanoparticle fraction was determined at different starting concentrations using high-performance liquid chromatography. In the case of fluphenazine, between 8 and 30% are assigned to the nanoparticles fraction, in the case of promethazine between 30 and 56%. The concentration of free active principle is reduced by about 99% for fluphenazine or by about 90% for promethazine. A loss of pharmacological activity of the neuroleptics is probable. The addition of promethazine to infusions of caffeine containing tea resulted in the formation of nanoparticles with a small size distribution; their mean size was comparable to the diameter of nanoparticles in pure tea infusions. In the case of fluphenazine the mean particle size grew with increasing concentration. Adding promethazine to infusions of decaffeinated tea resulted in the formation of nanoparticles with a broad size distribution. Two different size classes were formed after addition of fluphenazine. Caffeine and neuroleptics both take part in the formation of nanoparticles in caffeine containing tea. The particles were visualized using scanning electron microscopy. Molecular modelling calculations were performed to investigate probable geometries between neuroleptics and thearubigins.