Biol. Pharm. Bull. 28(12) 2225—2230 (2005)

the association of free radicals and other reactive oxygen species (ROS) to the pathogenesis of various diseases such as atherosclerosis, cancer, hypertension, ischemia-reperfusion, aging and age-related diseases. Antioxidants are believed to play an important role in preventing or alleviating chronic diseases by reducing the oxidative damage to cellular components caused by (ROS). Naturally occurring flavonoids, tannins, anthocyanins and other phenolic constituents are potential antioxidants. However, synthetic antioxidants such as tert-butyl hydroxyanisole (BHA) and tert-butyl hydroxytoluene (BHT) are known to have toxic and carcinogenic effects on human health. Therefore, substitution of synthetic antioxidants by natural ones and the screening of plant species for identifying new antioxidants have become critically important in recent years. Rumex japonicus HOUTT. (Family Polygonaceae) is a perennial herb with erect stems 40—100 cm long. Its leaves are long-petioled 10—25 cm long and 4—10 cm wide. It grows in wet meadows along ditches in the low lands of Japan, Korea and China. It has traditionally been used by the local people in Okinawa, Japan for treatment of acute and chronic cutaneous diseases and by Chinese as an effective drug for the treatment of constipation, jaundice, uterine hemorrhage and hematemesis. In this respect, major anthraquinones, emodin and chrysophanol, have been isolated and identified from the roots of R. japonicus, while the flavonoid quercitrin has been isolated from its leaves. Since the biological activities of extracts of R. japonicus aerial parts have not previously been reported, the objectives of this study were to (1) measure the antioxidant activities of different extracts of R. japonicus aerial parts, (2) measure the antibacterial activities of these extracts; and (3) identify the biologically active compounds of these extracts by GC-MS and HPLC.