Dissolution, solubility and cooperativity of phenolic compounds from Hypericum perforatum L. in aqueous systems.

The dissolution in water of phenolic constituents of St. John's wort (Hypericum perforatum L.) from a medicinal tea and a coated tablet formulation showed different dissolution profiles. In general, the flavonoid glycosides were well dissolved, followed by flavonoid aglycones and hypericin while hyperforin was only detectable at a very low level. Interestingly, hypericin exhibited much better extraction and dissolution rates than the similarly lipophilic hyperforin. When determining the octanol/water partition coefficient it became obvious that the solubility of pure hypericin in water increased upon addition of some phenolic constituents typical for Hypericum extracts. Most effective in solubilizing hypericin was hyperoside (hyperin, quercetin 3-O-beta-D-galactoside) which increased the concentration of hypericin in the water phase up to 400 fold in this model.