Novel Antioxidants Isolated from Perilla frutescens Britton var. crispa (Thunb.)

Two novel antioxidants (vinyl caffeate and trans-p-menth-8-en-7-yl caffeate) and seven known antioxidants (3,4-dihydroxybenzaldehyde, methyl 3,4-dihydroxy-benzoate, methyl caffeate, 3',4',5,7-tetra-hydroxy-flavone, caffeic acid, 6,7-dihydroxycoumarin, and rosmarinic acid) were isolated from Perilla frutescens Britton var. crispa (Thunb.). The redox potentials of the novel isolated antioxidative compounds were comparable to those of known antioxidants. trans-p-menth-8-en-7-yl caffeate was effective to prevent the oxidative degradation of perillaldehyde in the essential oil of P. frutescens.