The seeds of the coffee plant, grown in Arabia, yield the alkaloid caffeine (which is also obtained from plants belonging to different families, viz., Paullinia sorbilis, guarana). The coffee seeds also contain sugar, tannic acid, caffeic acid, a volatile oil, etc.

The qualities of coffee as a beverage are too familiar to need mention. In moderation, and when well made, it aids digestion and has laxative effect. In excess, or when improperly made and allowed to boil, it causes dyspepsia by the astringent action of its tannic acid. The plant itself is not official, but its alkaloid is so.