Raspberry ketone is a natural phenolic compound that is the primary

aroma compound An aroma compound, also known as an odorant, aroma, fragrance or flavoring, is a chemical compound that has a smell or odor. For an individual chemical or class of chemical compounds to impart a smell or fragrance, it must be sufficiently vo ...

of red raspberries.

Occurrence

Raspberry

ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...

occurs in a variety of fruits, including raspberries,

cranberries Cranberries are a group of evergreen dwarf shrubs or trailing vines in the subgenus ''Oxycoccus'' of the genus ''Vaccinium''. In Britain, cranberry may refer to the native species ''Vaccinium oxycoccos'', while in North America, cranberry ...

, and

blackberries The blackberry is an edible fruit produced by many species in the genus ''Rubus'' in the family (biology), family Rosaceae, hybrids among these species within the subgenus ''Rubus'', and hybrids between the subgenera ''Rubus'' and ''Idaeobatus' ...

. It is

biosynthesized Biosynthesis is a multi-step, enzyme- catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules ...

from

coumaroyl-CoA Coumaroyl-coenzyme A is the thioester of coenzyme-A and coumaric acid. Coumaroyl-coenzyme A is a central intermediate in the biosynthesis of myriad natural products found in plants. These products include lignols (precursors to lignin and lign ...

. It can be extracted from the fruit, yielding about 1–4 mg per kg of raspberries.

Preparation

Since the natural abundance of raspberry ketone is very low, it is prepared industrially by a variety of methods from chemical intermediates. One of the ways this can be done is through a crossed

aldol condensation An aldol condensation is a condensation reaction in organic chemistry in which two carbonyl moieties (of aldehydes or ketones) react to form a β-hydroxyaldehyde or β-hydroxyketone (an aldol reaction), and this is then followed by dehydration to ...

followed by

catalytic hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic ...

. First,

acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscib ...

is condensed with 4-hydroxybenzaldehyde to form an α,β-unsaturated ketone. Then the

alkene In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...

part is reduced to the

alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which ...

. 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 synthesis

Uses

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. Synthetic raspberry ketone is cheaper, with estimates ranging from a couple of dollars per pound to one fifth of the cost of the natural product.

Marketing

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

(acetone) group at their end, which is shared with

ketone bodies Ketone bodies are water-soluble molecules that contain the ketone groups produced from fatty acids by the liver (ketogenesis). Ketone bodies are readily transported into tissues outside the liver, where they are converted into acetyl-CoA (acetyl- ...

Safety

Little is known about the long-term safety of raspberry ketone supplements, especially since little research has been done with humans. Because it is chemically related to the stimulant

synephrine Synephrine, or, more specifically, ''p''-synephrine, is an alkaloid, occurring naturally in some plants and animals, and also in approved drugs products as its ''m''-substituted analog known as neo-synephrine. ''p''-Synephrine (or formerly Sympat ...

, there are some concerns about its safety. Toxicological models indicate a potential for

cardiotoxic Cardiotoxicity is the occurrence of heart dysfunction as electric or muscle damage, resulting in heart toxicity. The heart becomes weaker and is not as efficient in pumping blood. Cardiotoxicity may be caused by chemotherapy (a usual example is th ...

effects, as well as effects on reproduction and development. Furthermore, in many

dietary supplement A dietary supplement is a manufactured product intended to supplement one's diet by taking a pill, capsule, tablet, powder, or liquid. A supplement can provide nutrients either extracted from food sources or that are synthetic in order ...

s containing raspberry ketones, manufacturers add other ingredients such as

caffeine Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class. It is mainly used recreationally as a cognitive enhancer, increasing alertness and attentional performance. Caffeine acts by blocking binding of adenosine t ...

which may have unsafe effects. In 1965, the US

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...

classified raspberry ketone as generally recognized as safe (GRAS) for the small quantities used to flavor foods.

References

{{Authority control Flavors Food additives Ketones Perfume ingredients