| Research Abstract |
Rective oxygen species such as superoxide, hydroyl radical, and peroxy radical have been implicated in the aging process and in a wide variety of diseases such as cancer. Radiation induced tissue damage is also a direct result of free radical-mediated toxicity. Redox regulation is to maintain the homeostasis in vivo against oxidative stress by regulating redox state. In this study, explorative study on scavenging reactive oxygen species. The scavenging abilities were estimated with ESR spin-trapping method using DMPO as spin-trapping reagent for superoxide and hydroxyl radical, and for peroxyradical, decay of cumylperoxyradical was directry measured with ESR The antioxidants used in this study were the synthetic fluorochalcon, applephenon(extract from apple, polyphenol), vegetables (water soluble conponents), γ-tocotrienol, cathechin derivative, artepillin c(major component of Brajilian propolis), thiol containing compounds such as methionine and penicillamin. uperoxide was generated f
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rom hypoxantine-xantine oxidase system and hydroxyl radical was generated from Cu(en)2-H2O2 system, cumen peroxyl radical was generated from di-tert-butyl peroxide and cumene with a high pressure mercury lamp. Polyphenol derivative such as hydroxylcharcon derivative, applephenone, extravt from eggplant, showed high scavenging ability against hidroxyl radical as potent as gluthathion and trolox. Against superoxide, cathechin derivative and thiol-containing compound showed very high scavenging ability. Artepillin c shows high scavenging ability against peroxyl radical, conparable to (+)-cathechin. Generally, there are two mechanism of hydrogen-transfar reactions from phenolic compounds to radical species, i.e., a one-step hydrogen atom transfer or electron transfer followed by proton transfer. The examination of kinetics of hydrogen transfer for phenolic antioxidants with or without methala such as magnesium or scandium indicated that the hydrogen-transfer reaction of (+)-cathechin proceeds via electron transfer to radicals followed by proton transfer, and hydrogen-transfer reaction of Vitamin E and Artepillin C proceeds via one-step hydrogen atom transfer. protective effects of radioprotector and antioxidants in mice given a lethal dose (8 Gy) of X-ray irradiation was examined. 30 days survival rate for applephenon was 30%(control : 0%), and DRF8dose-reduction factor) afforded by POBN(α-(4-Pyridyl 1 -oxide)-N-tert-butylnitrone) was about 1.3. Less
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