Raspberry ketone

Raspberry ketone occurs in a variety of fruits, including raspberries, cranberries, and blackberries. It is released by orchid flowers, e.g. Dendrobium anosmum (syn D. superbum), and several Bulbophyllum species to attract raspberry ketone-responsive male Dacini fruit flies. It is biosynthesized from coumaroyl-CoA. It can be extracted from the fruit, yielding about 1-4 mg per kg of raspberries.

Since the natural abundance of raspberry ketone is low, it is prepared industrially by a variety of methods from chemical intermediates. One of the ways this can be done is through a Claisen-Schmidt condensation followed by catalytic hydrogenation. First, acetone is condensed with 4-hydroxybenzaldehyde to form an α,β-unsaturated ketone. Then the alkene part is reduced to the alkane. This two-step method produces raspberry ketone in 99% yield. There is a less expensive hydrogenation catalyst, nickel boride, which also demonstrates high selectivity towards hydrogenation of the double bond of enone.

Raspberry ketone is sometimes used in perfumery, in cosmetics, and as a food additive to impart a fruity odor. It is one of the most expensive natural flavor components used in the food industry. The natural compound can cost as much as $20,000 per kg.

Although products containing this compound are marketed for weight loss, there is no clinical evidence for this effect in humans. They are called "ketones" because of the ketone (acetone) group at their end, which is shared with ketone bodies.

Little is known about the long-term safety of raspberry ketone supplements in humans. Toxicological models indicate potential for cardiotoxicity and effects on reproduction and fetal development. No international regulatory authority has approved raspberry ketone as a weight loss supplement or established whether it is safe to use.

In 1965, the US Food and Drug Administration classified raspberry ketone as generally recognized as safe (GRAS) for the small quantities used to flavor foods.