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Limonin Functions

Limonin is one of a class called liminoids. It is found in citrus fruits. Comprised of carbon, hydrogen, and oxygen atoms, its molecular formula is C26H30O8 (limonoate D-ring-lactone). It is found in the pulp, skins, and seed of most citrus fruits including oranges, lemons, limes, and grapefruits.

Diagram of a limonin molecule

Within citrus fruits, it is bonded with a sugar molecule. When it comes in contact with acidic compounds, as it does when orange juice is made or it is digested in the body, the limonin molecule is broken from the sugar. In this form in the plant it acts as a means of protecting the plant from bacteria and viruses.

When orange juice or especially grapefruit juice are made, the acidic breakdown of the limonin glucoside molecule occurs over time giving the juice a more and more bitter taste. This has long been a problem for the citrus fruit industry causing investment in research on ways to nullify the bitter taste by either removing the limonin or causing it to combine with another substance.

Another, almost unexpected possibility was to find a valuable use for limonin. Limonin in the form of crushed seeds and skins is made into a syrup and has been used as an additive to cattle feed. Nevertheless, an even more valuable use is being considered for limonin. Because of the apparent health benefits of limonin research is now being done to determine whether it might be a powerful anti-cancer dietary supplement.

When limonin or limonin glucoside comes into the body it is absorbed into the bloodstream by the digestive system. It acts as a powerful antioxidant that prevents cell breakdown from free radicals and also seems to inhibit the growth of cancer. It is an "inducer" of GST, a tetoxifying agent.1

Another explanation of its cancer fighting ability can be found in a study that shows: "Phytochemicals may reduce chronic inflammation and cancer risk, in part, by modulating T-cell nuclear factor kappa B (NF-B) activation."2 This same study showed that "dietary combination with fish oil enhanced the suppressive effects".

One of the great advantages of limonin is that it has been found to have very high bioavailability in humans, which means that it is easily absorbed into the blood stream. Yet another advantage is that it is found to remain in the blood stream for as long as twenty-four hours after ingestion.

As a bonus, it also inhibits the production of cholesterol in the liver. In the presence of limonin, human liver cells produce less apo B, which helps to build bad cholesterol.

Next Page: Natural Sources of Limonin


  1. NRJournal
  2. Phytochemicals May Reduce Chronic Inflamation

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