Raspberry Ketone and its Anti-Obese Property

Raspberry Ketone (RK) is one of the most vital aromatic compound found in the red raspberry (Rubus idaeus) which is represented in Fig 1. It also goes by the name European red raspberry. It is one of the oldest fruits known to people and it is being used throughout the centuries. Humans generally used it for nutritional and medicinal purposes. Raspberry contains significant amount of healthy sugars, vitamins, minerals and many different polyphenols. Raspberry is quite popular around the world and comes just after strawberry and blueberry. 

Fig 1: Rubus idaeus

Scientists have studied many different biological effects of raspberry components but this anti-obese action it the one that has intrigue them the most. In 1996, scientists discovered ellagic acid present is raspberry helps to prevent or inhibit tumor inductions in the liver, lungs and esophagus. Scientists have not yet found any negative side-effects of RK in human. In 1982, they found in a 24 h period most of the RK gets excreted from the rodents' body through urine.

Raspberry also contains wide variety of secondary metabolites that gives raspberry its unique fragrance and flavor. Humans are extracting and isolating those aromatic compounds through ages. In 1982, scientists discovered RK to be the major component of those aromatic compound that gives unique scent and taste. Since then it is widely used in the cosmetics industry and food industry. The market demand for RK has sky-rocketed very quickly. A race to produce it synthetically has started.  

RK has a chemical formula of (4-(4-hydroxyphenyl) butan-2-one) and its molecular structure is represented by Fig 2. We can also find similarities in structure of RK with other metabolites like capsaicin and synephrine. These compounds are known to have anti-obese effects on rodents. They are also found to alter the lipid metabolism. 

Fig 2: RK

As stated before, capsaicin has the ability to decrease the adipose tissue weight and serum triacylglycerol content by enhancing the energy metabolism. Capsaicin is a pungent principle secondary metabolite that is commonly found in hot pepper. Synephrine is another secondary metabolite that is commonly found in the citrus plants. In 1999, scientists discovered synephrine is able to exert a lipolytic activity in the fat cells. Scientists noted the similarities between the molecular structure of these three compounds; RK, capsaicin and synephrine and performed experiments to understand if RK has a similar property to that of capsaicin and synephrine.  They hypothesized that RK might influence the lipid metabolism in a way similar to those two compounds. 

In 2004, scientists performed a unique experiment. To test the effect on obesity they designed a vivo experiment. Firstly, they fed the mice with high-fat diet that included 0.5,1 or 2% of RK for 10 weeks. Then after they fed the same mice a high-fat diet for the next 6 weeks. Following that they they again fed the mice with the high-fat diet that included 1% RK for the next 5 weeks. Scientists discovered that RK prevented the high-fat diet induced elevations in body weight. The weights gain of the liver and visceral adipose tissues like epididymal, retroperitoneal and mesenteric were also prevented. RK was also able to decrease the hepatic triacylglycerol content after they had been increased by a high-fat diet. It was then confirmed that RK increases norepinephrine-induced lipolysis that is associated with the translocation of hormone sensitive lipase in rat epididymal fat cells. These effects appear to come from action of RK in altering the lipid metabolism.

Scientists then concluded that RK prevents obesity and fatty liver and helps improve the health. 

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Reference:

Morimoto, C., Satoh, Y., Hara, M., Inoue, S., Tsujita, T., & Okuda, H. (2005). Anti-obese action of raspberry ketone. Life sciences, 77(2), 194-204.