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.
Synephrine is chemically very similar to the ephedrine and pseudo-ephedrine found in many OTC cold/allergy medications and in a number of weight loss and energy supplements which contain Ma Huang
Increases metabolic rate
Increases caloric expenditure
Promotes weight loss
Increases energy levels
Because synephrine is a stimulant, similar to caffeine and ephedrine, it is thought to have similar effects in terms of providing an energy boost, suppressing appetite and increasing metabolic rate and caloric expenditure.
Although synephrine and several other compounds found in zhi shi are structurally similar to ephedrine and are known to act as stimulants (via adrenergic activity), zhi shi does not appear to have the same negative central nervous effects of ma huang (ephedra)
The effects of synephrine alone or in combination with other ingredients such as kola nut and guarana (both are caffeine sources)) generally fall into the category of acting as a mild stimulant.
The extract of citrus aurantium, in addition to synephrine, also contains tyramine and octopamine. Octopamine may be related in some way to appetite control