Glucurunolactone is one of the main ingredients in energy drinks such as the well-known brand Red Bull. It is produced naturally in the human liver from glucose and regulates glycogen formation. Its immediate precursor is glucuronic acid. It is involved in detoxification of the liver through glucuronidation.
Human studies suggest that when glucurunolactone is administered orally, it is rapidly absorbed, metabolised and excreted, particularly in the form of glucaric acid.

¤ Glucuronidation is the most common form of ‘conjugation’ in the metabolism of mammals. This glucuroconjugation reaction is catalysed by the family of UDP-glucuronosyltransferases (UGT). The glucuronidation reaction adds glucuronic acid to a hydrophobic compound resulting in its inactivation and increased polarity. Glucuronides are very water-soluble which is why they are so easily eliminated in urine and bile. Glucuronidation is therefore an important stage in phase II mechanisms of detoxification.

¤ Glucuronidation helps in particular to eliminate drugs. In the course of doing so, the drugs sometimes use up glucuronolactone more quickly than it can be produced naturally by the body, reducing the levels of other substances such as glycogen. Glucuronolactone has been added to certain drugs to increase their tolerance and improve their elimination.

¤ Glucuronidation activates the excretion of bilirubin, an endogenous metabolite which eliminates toxins. During this reaction, the bilirubin undergoes an enzymatic reaction with a glucose derivative before being eliminated in the urine. In a study conducted with Red Bull, ten subjects were given 3 cartons of the drink or a placebo drink as a single dose. Blood samples were taken two hours after consumption, then every hour for the next four hours. Two hours after the Red Bull was absorbed, blood serum levels of bilirubin were significantly reduced, suggesting a detoxification effect. This is attributed to glucuronolactone and taurine.

¤ By eliminating steroids, glucuronidation also plays an important role in regulating levels of steroid hormones circulating in peripheral tissues.