This app contains in-depth information about medicinal herbs. Some plants contain phytochemicals that have effects on the body. There may be some effects when consumed in the small levels that typify culinary "spicing", and some herbs are toxic in larger quantities. For instance, some types of herbal extract, such as the extract of St. John's-wort (Hypericum perforatum) or of kava (Piper methysticum) can be used for medical purposes to relieve depression and stress.[medical citation needed] However, large amounts of these herbs may lead to toxic overload that may involve complications, some of a serious nature, and should be used with caution note.