Objective   To observe the protective effects of soybean isoflavones coordinated with folic acid and mechanism on rats.

  Methods   The pregnant rats were randomly divided into positive and negative control groups and five expreimental groups according to their body weight, cyclophosphamide were given to made the neural tube defects model.The biochemical indices were checked, the morphological changes of the embryos were checked through optical microscopy and transmission electron microscopy.

  Results   (1) The SOD activities increased while MDA、NO declined in every prevention groups.The changes showed dose-effect response relationship with soybean isoflavones; (2)The frequency of abnormalty decreased, moreover there was the best effect in the group of folic acid coordinated with 40 mg/L soybean isoflavones; (3)The develop mental index of embories significantly improved compared with the model-making grouop; (4)Under optical microcopy and transmission electron microscopy, the nucleus and the organelles were not significantly damaged or the impairment were diminished.

  Conclusion   Soybean isoflavones showed strong antioxidant effect coordinated with folic acid in a conformateddose which can decreased frequency of abnormalty more effectively than folic acid alone.