Herb-Drug Interactions: The effect of herbs, other PLANTS, or PLANT EXTRACTS on the activity, metabolism, or toxicity of drugs.Echinacea: A genus of perennial herbs used topically and internally. It contains echinacoside, GLYCOSIDES; INULIN; isobutyl amides, resin, and SESQUITERPENES.Hydrastis: A plant genus of the family RANUNCULACEAE. Members contain BERBERINE.Kava: Dried rhizome and roots of Piper methysticum, a shrub native to Oceania and known for its anti-anxiety and sedative properties. Heavy usage results in some adverse effects. It contains ALKALOIDS; LACTONES; kawain, methysticin, mucilage, STARCH, and yangonin. Kava is also the name of the pungent beverage prepared from the plant's roots.Plant Preparations: Material prepared from plants.Cimicifuga: A plant genus of the family RANUNCULACEAE that contains triterpenoid saponins. Remifemin from C. racemosa is used to suppress LUTEINIZING HORMONE. It is reclassified by some to ACTAEA. The common name of black snakeroot is also used with ASARUM and SANICULA.Herbal Medicine: The study of medicines derived from botanical sources.Milk Thistle: The plant Silybum marianum in the family ASTERACEAE containing the bioflavonoid complex SILYMARIN. For centuries this has been used traditionally to treat liver disease. Silybum marianum (L.) Gaertn. = Carduus marianus L.Hypericum: Genus of perennial plants in the family CLUSIACEAE (sometimes classified as Hypericaceae). Herbal and homeopathic preparations are used for depression, neuralgias, and a variety of other conditions. Hypericum contains flavonoids; GLYCOSIDES; mucilage, TANNINS; volatile oils (OILS, ESSENTIAL), hypericin and hyperforin.Ginkgo biloba: The only specie of the genus Ginkgo, family Ginkgoacea. It is the source of extracts of medicinal interest, especially Egb 761. Ginkgo may refer to the genus or species.Epimedium: A plant genus of the family BERBERIDACEAE which is used in DRUGS, CHINESE HERBAL. Members contain flavonol glycosides including epimedins, icariin and noricariin.Plant Extracts: Concentrated pharmaceutical preparations of plants obtained by removing active constituents with a suitable solvent, which is evaporated away, and adjusting the residue to a prescribed standard.Phytotherapy: Use of plants or herbs to treat diseases or to alleviate pain.Plants, Medicinal: Plants whose roots, leaves, seeds, bark, or other constituent parts possess therapeutic, tonic, purgative, curative or other pharmacologic attributes, when administered to man or animals.Drugs, Chinese Herbal: Chinese herbal or plant extracts which are used as drugs to treat diseases or promote general well-being. The concept does not include synthesized compounds manufactured in China.Cytochrome P-450 Enzyme System: A superfamily of hundreds of closely related HEMEPROTEINS found throughout the phylogenetic spectrum, from animals, plants, fungi, to bacteria. They include numerous complex monooxygenases (MIXED FUNCTION OXYGENASES). In animals, these P-450 enzymes serve two major functions: (1) biosynthesis of steroids, fatty acids, and bile acids; (2) metabolism of endogenous and a wide variety of exogenous substrates, such as toxins and drugs (BIOTRANSFORMATION). They are classified, according to their sequence similarities rather than functions, into CYP gene families (>40% homology) and subfamilies (>59% homology). For example, enzymes from the CYP1, CYP2, and CYP3 gene families are responsible for most drug metabolism.