Synephrine occurs in virtually all citrus products, and is consumed by humans in small amounts if citrus is included the diet. A wide variety of citrus materials containing synephrine are used in Chinese medicine and have generally been regarded as non-toxic; indeed, synephrine is used as a marker for chemical identification and relatively high synephrine content is a measure of herb quality. Positive effects of synephrine, mainly for anti-allergy applications, has been reported in the literature. The crude herb materials that contain synephrine, such as citrus (chenpi) and chih-shih (zhishi), have been reported to have anti-allergy effects, which are also partly due to their flavonoid content (e.g., hesperidin, nobiletin). In Chinese literature, these herbs are described as non-toxic. A combination of zhiqiao, chenpi, and foshou is included in a Chinese remedy called Weisu Granules, used for treating stomach upset and abdominal distention.
Following is a description of synephrine and the citrus materials, their pharmacology, clinical applications, and toxicology. SYNEPHRINE
Synephrine is found mainly in the medicinal products derived from citrus; it is also present in small amounts in the Chinese herb evodia. The alkaloids appear to be present in slightly higher quantities in the unripe fruit than in the ripe fruit (2). The amount of synephrine in blue citrus (qingpi), an immature citrus fruit, is 0.26% and in citrus (chenpi), a mature citrus fruit, the level is 0.22% (3). In an evaluation of four different dried citrus fruits used in Japanese herbal medicine, the content of synephrine did not show much difference (4). Some citrus materials that have been assayed in China have a higher synephrine content; in one study, synephrine levels in citrus fruits and peels ranged from as little 0.1% to a very high 2.0% (9), while most reports place the level at about 0.25%.