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Alkaloids are bitter-tasting chemicals, very widespread in nature, and often toxic, found in many medicinal plants.  There are several classes with different modes of action as drugs, both recreational and pharmaceutical. Medicines of different classes include atropine , scopolamine , and hyoscyamine (all from nightshade ),  the traditional medicine berberine (from plants such as Berberis and Mahonia ), [b] caffeine ( Coffea ), cocaine ( Coca ), ephedrine ( Ephedra ), morphine ( opium poppy ), nicotine ( tobacco ), [c] reserpine ( Rauwolfia serpentina ), quinidine and quinine ( Cinchona ), vincamine ( Vinca minor ), and vincristine ( Catharanthus roseus ).