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7,8,3',4',5'-Pentahydroxyisoflavone (8,3',5'-trihydroxydaidzein) and 6,7,8,3',4',5'-hexahydroxyisoflavone (6,8,3',5'-tetrahydroxydaidzein) are synthesized via a simple and effective method using commercially available daidzein as a raw material. Their structures are confirmed using spectroscopic analyses (infrared, nuclear magnetic resonance, and mass spectrometry), and their purities are determined by high-performance liquid chromatography. The antioxidant capacities are investigated by utilizing 1,1-diphenyl-2-picryl-hydrazyl radical scavenging, superoxide radical scavenging, nitric oxide radical scavenging, reducing power, and phosphomolybdenum assays. The antihypoxia activity is examined using a hypoxia-induced PC12 cell injury model. The antioxidant and antihypoxia abilities of 8,3',5'-trihydroxydaidzein and 6,8,3',5'-tetrahydroxydaidzein are greatly improved in comparison with daidzein. These results indicate that 8,3',5'-trihydroxydaidzein and 6,8,3',5'-tetrahydroxydaidzein are excellent antioxidant agents and can be used for alleviating injury induced by hypoxia. [ABSTRACT FROM AUTHOR]

In the present study, 6,8-dihydroxydaidzein (6,8-DHD or 6,7,8,4′-tetrahydroxyisoflavone) and 6,8,3′-trihydroxydaidzein (6,8,3′-THD or 6,7,8,3′,4′-pentahydroxyisoflavone) were synthesized via a facile and efficient way using commercially available formononetin as starting material. Their structures were confirmed using spectroscopic analyses (infrared, nuclear magnetic resonance, and mass spectrometry). The purity was checked by ultra-high performance liquid chromatography. Their antioxidant activities were evaluated via 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay and reducing power assay using ascorbic acid (vitamin C) as a reference compound. The antihypoxia capacity was determined by a hypoxia injury model in PC12 cells. Our study revealed that 6,8-DHD and 6,8,3′-THD exhibited higher antioxidant activities than that of vitamin C and could protect PC12 cells against hypoxia-induced damage. These results indicate that 6,8-DHD and 6,8,3′-THD are excellent antioxidant agents and could be used for alleviating injury induced by hypoxia. [ABSTRACT FROM AUTHOR]