Thearubigins are polymeric polyphenols that are formed during the enzymatic oxidation (called fermentation by the tea trade) of tea leaves. A large concentration of thearubigin is therefore found in black (fully oxidated) teas, and a very low concentration in unoxidized teas such as white and green teas. The health benefits of oxidized teas can be partially attributed to the antioxidant properties of thearubigins. While unoxidized tea lacks a high concentration of thearubigins, it still has antioxidant properties which are primarily due to its high concentration of catechin type polyphenols. Catechins are converted to theaflavins such as thearubigin during the oxidation process.