The Bitter Orange tree is indigenous to eastern Africa, Arabia, and Syria, and cultivated in Spain, Italy, and North America. The dried outer peel of the fruit of Bitter Orange, with the white pulp layer removed, is used medicinally. The leaves are also commonly used in many folk traditions. It is also called seville orange, zhi shi, chongcao, green orange, and sour orange.

The Botanical name for Bitter Orange is Citrus Aurantium and it's main "active" compound is Synephrine. 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. But Synephrine differs from ephedrine in that Synephrine is considered a semi-selective sympathomimetic (because it targets some tissues such as fat, more than it targets others such as the heart) versus a non-selective sympathomimetic (like ephedra which targets many tissues equally and thus often causes side effects).

Bitter Orange is a strong energy & fat burning herb and helps your body permanently increase the rate at which your metabolism burns calories and fat. Synephrine is the primary active alkaloid in Bitter Orange. Synephrine stimulates your body’s adrenal gland promoting effective fat burning, appetite suppression and natural energy.

For example, although some high-dose ephedra-containing supplements have been associated with certain cardiovascular side effects as elevated blood pressure and heart palpitations, researchers at Mercer University in Atlanta have shown that Synephrine containing Citrus aurantium extract, "Bitter Orange" (because it targets fat tissue rather than heart tissue) has no effect on hemodynamics such as heart rate and blood pressure.

Because Synephrine is a mild stimulant similar in some ways 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. There is a great deal of research currently underway into the weight loss benefits of Synephrine and supplements with related thermogenic effects, leading researchers in the Department of Physiology at Georgetown University to conclude that Citrus Aurantium, "Bitter Orange" may be the best thermogenic substitute for ephedra.