Mate products are sometimes marketed as "caffeine-free" alternatives to coffee and tea, and said to have fewer negative effects. This is often based on a claim that the primary active xanthine in mate is "mateine". This is wrongly said to be a stereoisomer of caffeine (it is not chemically possible for caffeine to have a stereoisomer). "Mateine" is an official synonym of caffeine in the chemical databases. So mateine "is" caffeine.