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Background : A brown seaweed, Saccharina longissima ( Laminaria angustata var. longissima ) has been consumed in Okinawa for 300 years. It is native to the southernmost part of Japan, in Okinawa, but grows on the Pacific coast (Kushiro and Nemuro) in Hokkaido in the northernmost part of Japan. Previously, we reported the structural characteristics from S. longissima . The fucoidan consisted of L-fucose, D-galactose, D-glucose, D-xylose, D-glucuronic acid, and sulfuric acid. This fucoidan activated the RAW 264.7 murine macrophage cell line. The aim of this study was to investigate the effects of a fucoidan isolated from Saccharina longissima on cell anti-proliferation and apoptosis in the U937 human leukemia monocyte lymphoma cell line. Methods : U937 cells were incubated with four fucoidan concentrations. The degree of apoptosis was determined using the APOPercentage APOPtosis assay, caspaer-3 activity assay and Western blotting analysis assay. Results : The treatment of cell with a fucoidan highly substituted with sulfate, in addition to L-fucose residues, inhibited cell growth. Apoptosis increased in U937 cells in a dose-dependent manner following the addition of fucoidan. However, the fucoidan did not induce apoptosis in the presence of caspase inhibitor (z-VAD-FMK). Conclusions : The fucoidan from Saccharina longissima induced apoptosis in U937 cells. Accordingly, the kelp containing this fucoidan may contribute to the observed longevity of the Okinawan population. Keywords: fucoidan, Saccharina longissimi, brown seaweed, traditional food, human leukemia cells, apoptosis

The effectiveness of cancer chemotherapy is often limited by the toxicity to other tissues in the body. Therefore, the identification of non-toxic chemotherapeutics from herbal medicines remains to be an attractive goal to advance cancer treatments. This study evaluated the cytotoxicity profiles of 364 herbal plant extracts, using various cancer and normal cell lines. The screening found occurrence of A549 (human lung adenocarcinoma) specific cytotoxicity in nine species of herbal plants, especially in the extract of Arctium lappa L. Moreover, purification of the selective cytotoxicity in the extract of Arctium lappa L. resulted in the identification of arctigenin as tumor specific agent that showed cytotoxicity to lung cancer (A549), liver cancer (HepG2) and stomach cancer (KATO III) cells, while no cytotoxicity to several normal cell lines. Arctigenin specifically inhibited the proliferation of cancer cells, which might consequently lead to the induction of apoptosis. In conclusion, this study found that arctigenin was one of cancer specific phytochemicals, and in part responsible for the tumor selective cytotoxicity of the herbal medicine.