Most pharmaceutical drugs are single chemical entities that are highly refined and purified and are often synthesized. In 1987 about 85% of modern drugs were originally derived from plants. Currently, only about 15% of drugs are derived from plants. In contrast, herbal medicines are prepared from living or dried plants and contain hundreds to thousands of interrelated compounds. Science is beginning to demonstrate that the safety and effectiveness of herbs is often related to the synergy of its many constituents.