Mechanism of Action
During metabolism, in the Krebs cycle, citrates are converted into acetyl coenzyme A with the help of an enzyme system, citrate lyase (Majeed et al., 1994). When (-)hydroxy- citrate is present along with citrate during this phase, part of the enzyme will be utilized by this acid, and thereby formation of acetyl coenzyme A is slowed. The acetyl unit is the building block of fat synthesis. Therefore, consumption of (-)hydroxycitric acid brings about a slowing of fat synthesis and hence of fat accumulation. But for effective intervention, hydroxycitric acid has to be in the straight chain form and not as a lactone. This is achieved by conversion into a metal derivative. Calcium hydroxycitrate is liberated to give free acid, which remains in straight chain form for some time so that it can function effectively. The best time to take the calcium salt is about 1 hour before the main meal. As part of the marketing process, some micronutrients are added to increase its value.
The role of hydroxycitric acid as an inhibitor of ATP-citrate lyase, as well as its structure and characteristics, has been reviewed (Yamada et al., 2007).