All the tea types are subjected to varying degrees of oxidation which affects their flavonoids profile. Green teas have more catechins, the more simple flavonoids. Black teas, after undergoing a full oxidation process, have the more complex flavonoids called theaflavins and thearubigins. Oolong teas contain a flavonoids' profile between black and green teas.
Research indicates that overall antioxidant activity and levels remain similar across the tea spectrum.
All these teas are a rich source of natural plant-derived antioxidant compounds called polyphenols. Included within the broad antioxidant polyphenol class are flavonoids. These compounds are found in tea leaves and may provide protective antioxidant action against harmful free radicals. Research shows that free radicals contribute to the cause of many common diseases including heart disease and some forms of cancer