Suppressive effects of Okinawan food items on free radical generation from stimulated leukocytes and identification of some active constituents: implications for the prevention of inflammation-associated carcinogenesis.

Okinawa prefecture in Japan is a distinct area characterized by unique traditional food habits and longevity. Prolonged exposure to activated leukocytes, playing pivotal roles in chronic inflammation-associated carcinogenesis, is known to lead to oxidative and nitrosative damage to macromolecules in the body since they are primary sources of free radicals, such as superoxide anion (O(2)(-)) and nitric oxide (NO). In this study, we estimated anti-oxidative and anti-nitrosative activities of Okinawan food items by employing two cellular experimental systems: (1) phorbol ester-induced O(2)(-) generation from differentiated HL-60 human promyelocytic leukemia cells; and (2) lipopolysaccharide (LPS)-induced NO generation in RAW264.7 murine macrophages. A total of 138 food items, consisting of 42 samples unique to Okinawa and 96 common in the Japanese main island, were purchased at local markets in Okinawa and extracted with chloroform. When tested at a concentration of 100 microg/ml, 38% (16/42) of the former showed 70% or more inhibition of O(2)(-) generation while 21% (20/96) of the latter did so. In parallel, 64% (27/42) of the former showed significant NO generation suppression in contrast to 48% (46/96) of the latter . Twenty-one active species were further tested at a concentration of 20 mug/ml, and eleven species, including sugar cane, wild turmeric, and zedoary, were indicated to be most promising items with anti-oxidative and anti-nitrosative properties. In addition, some of the active constituents (chebulagic acid, a resveratrol derivative, and sesquiterpenoids) were identified. Our results suggest that food items typical in the Okinawa area have higher cancer preventive potential than those common in Japan.

Growth inhibitory activities of crude extracts obtained from herbal plants in the Ryukyu Islands on several human colon carcinoma cell lines.

There is increasing interest in the use of herbs for the treatment of human diseases including cancer. Therefore, the purpose of this study was to determine whether crude extracts obtained from 44 herbal plants in the Ryukyu Islands might contain components capable of inhibiting the growth of a variety of human colon carcinoma cell lines. Leaves, roots and other parts of the plants were extracted with chloroform, and the crude extracts were dissolved in dimethylsulfoxide and used for the experiments. Extracts of Hemerocallis fulva, Ipomoea batatas, Curcuma longa, and Nasturium officinale caused marked dose-dependent growth inhibition, with IC(50) values in the range of 10-80 mug/ml. With the HCT116 cell line, the extracts of Hemerocallis fulva and Ipomoea batatas induced G1 cell cycle arrest after 48 h of treatment. In addition, we found that extracts of Curcuma longa, and Nasturium officinale induced apoptosis in these cells after 48 h of treatment. The present studies are the first systematic examination of the growth inhibitory effects of crude extracts obtained from herbal plants in the Ryukyu Islands. The findings provide evidence that several plants in the Ryukyu Islands contain components that may have anticancer activity.