Citrus aurantium is commonly referred to as bitter orange. Zhi shi is the immature dried fruit of citrus aurantium. Zhi shi has bee used in Traditional Chinese Medicine to treat chest congestion and stimulate gastrointestinal functions. In recent years this supplement has been promoted for appetite control.
The extract of bitter orange (and bitter orange peel) has been used in dietary supplements as an aid to fat loss and as an appetite suppressant; although in traditional Chinese medicine it is always prescribed in concert with other support herbs, not in isolation. Bitter orange contains synephrine, a substance, which acts on the α1 adrenergic receptor to constrict blood vessels and increase blood pressure and heart rate. Synephrine is the main "active" compound found in the fruit of a plant called Citrus aurantium. The fruit is also known as zhi shi (in traditional Chinese medicine), and as green orange, sour orange and bitter orange in other parts of the world.