Gentian root has a long history of use as an herbal bitter and is an ingredient of many proprietary medicines. The name is a tribute to Gentius, an Illyrian king who was thought to have found out that the herb had tonic properties.
The bitter principle of gentian root is primarily gentiopicrin (also called gentiopicroside), a glycocide. A 2007 paper by a Japanese group identified 23 compounds in fresh gentian root. Gentiopicrin was absent from fresh root, so it possibly develops during drying and storage of the root.
"Just how long have the benefits of bitter herbs been known? In Traditional Chinese Medicine, an intact system of medicine that is more than 5,000 years old, gentian was called lung tan, meaning dragon’s gall because of its exceedingly bitter taste. Bretschneider, physician to the Russian Legation at Peking in the late 19th century, wrote in his Botanicon Sinicum that gentian was first recorded from around the time of Christ in the Shen nung Pen ts’ao king, one of China’s oldest and most revered works on materia medica. Traditionally, the Chinese did not usually differentiate individual species of a genus, and thus lung tan could have been any number of Gentiana species, although the most important species used today is Gentiana scabra, known as Lung-tan. Since the days of the Pen King, and probably before the beginning of recorded history, this herb has been used in China to help ease a variety of ailments." Dr. Christopher Hobbs: Gentian A hard pill to swallow