The isoflavonoids content and antioxidant activity in different sections of Pueraria lobata roots, including the root outer bark, kudzu root and whole root were investigated in this study. Isoflavonoid concentrations in P. lobata roots were determined by high performance liquid chromatography. The antioxidant activity of P. lobata roots was assessed by total phenol content, DPPH free radical scavenging assay, ABTS free radical scavenging assay and reducing power. The root outer bark of P. lobata root possessed higher isoflavonoids content than whole root or kudzu root (p < 0.05). The levels of antioxidant potential of the root outer bark assayed by total phenolic content, DPPH, ABTS and reducing power were significantly higher than those of the whole root or the kudzu root (p < 0.05). The main isoflavonoids in all sections of P. lobata roots were puerarin, daidzin, daidzein, genistin and genistein. The major isoflavonoid puerarin in root outer bark exhibited the greatest antioxidant activity in P. lobata roots.

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