Hypericum perforatum varieties

Flavonoids in the diet have been widely promoted as important antioxidant contributors. Their neuroprotective properties, because of this effect, have been demonstrated by several workers. However, they have also been demonstrated to have MAOI activity and this has been proposed as part of the explanation of the use of the common herb, St Johns Wort, Hypericum perforatum L., as an antidepressant. This dual role has now been proposed for a variety of flavonoids, such as kaempferol (22) from the leaves of Ginkgo biloba L., a widely used herbal product which has been suggested as a preventative agent against neurodegeneration. Quercetin (23), similarly, has also shown to inhibit MAO-B " and reverse the effects of induced catalepsy, which mimics the bradykinesia associated with PD. Tangeretin (24) also inhibits MAO-B and crosses the blood brain barrier in a rat model. 

St John s Wort (Hypericum perforatum, S JW) has been on the herbal pharmacopeia for many years. It is a traditional remedy for depression which has been validated in recent randomized clinical trials. Like many herbal preparations levels of active constituents vary from one preparation to another. As a consequence of its validation as an active preparation it has been widely promoted. Recently it has been shown to interact with a variety of other substances probably through the process of drug interaction. 

Some thirteen different varieties of St. John s Wort flourish in England, but Hypericum perforatum is the only one included in the herbal materia medica, and may be distinguished from the others by the small hole-like dots on the leaf. 

The market for herbal medieines and supplements in the Western world has markedly inereased in reeent years, and, not surprisingly, reports of interactions with conventional drugs have arisen. The most well known and documented example is the interaetion of St John s wort (Hypericum perforatum) with a variety of drugs, see below. There have also been isolated reports of other herbal drug interactions, attributable to various mechanisms, including additive pharmaeological effects. 

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