| Antioxidation is defined that the antioxidant prevents free radicals form producing, or eliminates them. In the past decades, along with the rapid development, of molecular biology, gerontology and food science, antioxidation has been attracting more and more attention for its important roles in medical treatment, health care and food storage. In this paper, potential antioxidative effectiveness of twelve weedy plants and 5 crop residues in paddy fields were evaluated by determining their optical density values of the extracts got by alcohol using spectrophotometry. The results were showed as follows.1 Evaluation of potential antioxidative activities of weedy plants and grain crop residuesThe OD values, the implication of antioxidizing ability of chemical matters, of the extracts from Echinochloa crusgalli, Leptochloa chinensis , Cyperus irin and Monochoria vaginalis with 8 h extraction are 0.0165, 0.0215, 0.0235 and 0.0120 respectively, indicating that their antioxidizing activity were significandy stronger than that of tea polyphenols. They had similar antioxidizing effectiveness to that of medicinal plant Elsholtzia dliate. Weedy plant species Alternanthera philoxcroides and Gyporus rotundus had same antioxidizing ability to that of tea polyphenols. Cyperus difformis, Juncellus serotinus, Lemna minor, Marsilea quadrifolia, Paspalum paspabidesh had a weak antioxidizing ability and no antioxidizing activity was found in Ludwigia prostrate. The antioxidizing activity of those extracts were also found changeable depending upon the extracting method.2 The optimization of extracting condition for active antioxidizing components from Monochoria vaginalisBased on an orthogonal experimental designation of extraction condition for antioxidizing factors from Monochoria vaginalis solvents, temperature and ratio of solvent to sample matter and extracting time were considered. Four kinds of solvents, i. e. watercontained 0.3% antioxidant, ethylalcohol anhydride, acetidin and petroleum, ether were used in the treatments of ckcumfluence collection. Effects of the ratio of solvent quantity and sample material, temperature, period on the antioxidizing agents extraction were studied. The results showed that to achive the best harvest of antioxidizing activity from Monochoria vaginalis, a solvent of water containing 0.3% antioxidant, with a ratio of 12:1 (solvent to sample material) at 80 °C for 8 h was the optimized antioxidant-collecting parameters. The optimization of the collecting condition varied responded upon the the solvent. When the solvent adopted was alcohol, the optimized condition for extraction was the ratio of 10:1 at 80°C for 2 h. When the solvent adopted was changed to ethyl acetate, the optimized condition for extraction was the ratio of 12:1 at 60°C for 6 h. When petroleum ether was adopted as solvent, the best condition for extracting the active component from Monochoria vaginalis was the ratio of 10:1 at 20°C for 8 h.3 Analysis of active antioxidizing components in Monochoria vaginalisIsolating the crude extracted components by 75% alcohol from Monochoria vaginalis was pursued and was seperated into four parts in petroleum ether, dichloromethane, ethyl acetate and nbutanol. Higher antioxidizing activity was detected in the nbutanol phase by means of iodine method The result also showed the alcohol-extracted component including rich content (1.6508mg. g"1) of flavonoids. Also the free seedling of Monochoria vaginalis showed a significant SOD enzyme activity.4 Isolated and identified of active substances being of antioxidation in Monochoria vaginalisUsing the chromatography and MP^ IR> HR-MS> 'HNMIU 13CNMR> 'H-1HCOSY> 1H-13CCOSY> HMBC\ HSQC and other methods, two chemicals are isolated and identified from the 70% alcohol-extracted compound. Main active components in the extact from Monochoria vaginalis at least included flavonoids and phenols..
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