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Methods. Twelve different types of Chinese teas, including green, semifermented, and black tea, were studied for their antioxidant activities and active components. Compositions of (−)-epicatechin, (−)-epigallocatechin, (−)-epicatechin gallate, (−)-epigallocatechin gallate, and gallic acid were identified by fast atom bombardment-mass spectrometry and high-performance liquid chromatography-mass spectrometry and quantified by high-performance liquid chromatography. Antioxidant activities in lard were measured by the Rancimat method.

Results. The results showed that both yields of polyphenol extract and antioxidant activities varied with different tea processing methods. It was found that (−)-epigallocatechin gallate, (−)-epigallocatechin, and (−)-epicatechin gallate inhibited soybean lipoxygenase at the IC₅₀, values ranging from 10 to 20 μM.