 Guaranine, theine, and mateine are all synonyms for caffeine when the definitions of those words include none of the properties and chemicals of their host plants except caffeine.Natural sources of caffeine contain widely varying mixtures of xanthine alkaloids other than caffeine, including the cardiac stimulants theophylline, theobromine and other substances such as polyphenols, which can form insoluble complexes with caffeine.The main natural phenols found in guarana are (+)-catechin and (-)-epicatechin.