Structure of Cycasin and Macrozamin

CYCASIN

Cycasin is found in all the cycad genera (De Luca 1980) It is the most common cycad gylcoside, others include macrozamin and neocycasin. The active component of all theses compounds is MAM (methylazoxyglycoside), which is metabolised to a toxic intermediate by the p450 enzyme present in the liver and in the olfactory epithelium in the nose (Seawright et al. 1995).

Cleavage of Cycasin to yield MAM

To release MAM, Cycasin must be cleaved. This cleavage is made by the enzyme betaglucosidase which is found in microbes in the gut. For this reason cycasin must be taken orally in order to be toxic. Although MAM is proven to be hepatotoxic and carcinogenic (Hoffman and Morgan 1983, 1984), no studies have found it to have a neurotoxic effect apart from work by Jones et al. (Jones 1972) which showed toxicity to neurons of newborn mice.