Three antioxidants were isolated: (-)-epigallocatechin and (-)-epigallo catechin gallate from Theae Folium generally called green tea, and gallic acid from Moutan Cortex. They inhibited Fe^(3+)-ADP/ascorbate-induced lipid peroxidation in rat liver microsomal fraction, showing IC_(50), the concentration of antioxidants which is required to inhibit 50% of the peroxidation for microsomal membranes at 1 ㎎ protein/㎖, to be 0.2 ㎍/㎖, 0.4 ㎍/㎖ and 2.5 ㎍/㎖, respectively.