Biochemical activities of extracts from Hypericum perforatum L. 2nd Communication: inhibition of metenkephaline- and tyrosine-dimerization.

Extracts from the herb "St. John's wort" (Hypericum perforatum L.), besides other activities such as wound healing, antigout, antirheumatic and diuretic properties, are widely used to counteract neurological disorders such as depressive situations, nervousness and sleeplessness. The characteristic and leading component in these extracts, the dianthraquinone hypericin, is very likely not to represent the main active principle mediating the desirable effects. Thus, standardization of the drug is no longer based on the quantification of total hypericin and since several years simply the determination of dry matter content is in use instead. As biochemical background of depression the lack of catecholamine neurotransmitters or decreased beta-endorphins such as methionine- or leucine-enkephalins have to be envisaged. This communication reports on the inhibition of myeloperoxidase-catalyzed dimerization of enkephalins by Hypericum extracts. The substitution for enkephalins by tyrosine and for myeloperoxidase by horseradish peroxidase may represent a simple and inexpensive biochemical model reaction of pathological events during the manifestation of depressive events suitable for drug standardization.