Green tea leaf is prepared from the steamed and dried fresh leaves of Camellia sinensis (L.) Kuntze [Fam. Theaceae].
Tea contains polyphenols (catechins), flavonols, methylxanthines (notably caffeine, theophylline, and theobromine).
Some commercial green tea extracts are standardized to approximately 60% polyphenols.
Green tea and its preparations are usually not prescribed as a medication.
Research has shown the beneficial effects of green tea at dosages normally consumed by humans.