Also known as Seville orange, sour orange, and Zhi shi, bitter orange has been used in traditional Chinese medicine and by indigenous people of the Amazon rain forest for nausea, indigestion and constipation.

Current uses of bitter orange are for heartburn, loss of appetite, nasal congestion and weight loss. Users also apply it to skin for fungal infections such as ringworm and athlete’s foot.

Bitter orange has been used as a substitute for ephedra, a dietary supplement for weight loss now banned by the U.S. Food and Drug Administration (FDA). The dried fruit and peel of bitter orange (and sometimes the flowers and leaves) are taken by mouth in extracts, tablets and capsules. Bitter orange oil also can be applied to the skin.

The National Institute of Standards and Technology (NIST) has developed Standard Reference Materials (SRMs) for bitter orange. Researchers can use the new materials to develop and test analytical methods for compounds in bitter orange, or as control materials for quality assurance of their measurements.

The NIST samples do not offer scientific evidence to address the use of bitter orange for health purposes.

The National Institute of Health’s (NIH) National Center for Complementary and Alternative Medicine (NCCAM) affirms that “there is not enough scientific evidence to support the use of bitter orange for health purposes.” It notes “many herbal weight-loss products now use bitter orange peel in place of ephedra. However, bitter orange contains the chemical synephrine, which is similar to the main chemical in ephedra. The U.S. FDA banned ephedra because it raises blood pressure and is linked to heart attacks and strokes: it is unclear whether bitter orange has similar effects. There is currently little evidence that bitter orange is safer to use than ephedra.”

NIST supplies standardized samples of bitter orange in three forms that represent different analytical measurement challenges: ground fruit, extract and solid oral dosage form (tablets).

The new bitter orange reference materials include SRM 3258 (ground fruit), SRM 3259 (extract) and SRM 3260 (solid oral dosage form). In addition the three SRMs are packaged together as SRM 3261. The SRM materials for analysis and measurement come with certified concentration values for synephrine, octopamine, tyramine, N-methylytramine, hordenine, total alkaloids and caffeine.

Partial support for the development of the bitter orange SRMs was provided by NIH’s Office of Dietary Supplements and the FDA Center for Drug Evaluation and Research (CDER).