- Chemical studies on antioxidant mechanism of tea catechins: analysis of radical reaction products of catechin and epicatechin with 2,2-diphenyl-1-picrylhydrazyl. Sang, S., Cheng, X., Stark, R.E., Rosen, R.T., Yang, C.S., Ho, C.T. Bioorg. Med. Chem. (2002)