The term herbal medicine is something of a misnomer. Although they do not fit the botanical definition of herb, the bark of trees and rhizomes, roots, and bulbs serve as the basis of many plant remedies. Herbs usually contain more than one active ingredient. In some cases, herbal remedies are made from more than one plant. In contrast, pharmaceutical drugs derived from plants generally consist of a only one compound isolated from a plant.
Herbal remedies vary widely.
In some cultures, they are are likely to be dried and chopped or pulverized into powders to be used in teas or infusions. In others, they may be extracted to standard specifications and formed into tablets or capsules. In Europe, where many herbal remedies are available only by prescription, the standards for herbal extracts are set by the German Commission E. Standardized botanical products are made from raw plant material, but they contain a minimum amount of the substance or substances most important for therapeutic effects. Pharmaceutical companies have taken this process a little farther and have isolated only the substance that appears to be responsible for a herb's effectiveness. In the mid-1950s, the pharmaceutical company, Eli Lilly, began screening medicinal plants for antitumor activity, selecting plants used in traditional medicine.