A comparative study on aqueous root extracts of Pueraria thomsonii and Pueraria lobata by antioxidant assay and HPLC fingerprint analysis

The roots of Pueraria thomsonii and Pueraria lobata are officially recorded in Chinese Pharmacopoeia under the same name Radix Puerariae. However, the aqueous root extract of Pueraria lobata showed more potent antioxidant activity than that of Pueraria thomsonii. A qualitative HPLC method was developed to compare the chemical profiles of Pueraria thomsonii and Pueraria lobata, which revealed four major common peaks (daidzein 1, daidzin 2, puerarin 3 and 5-hydroxypuerarin 4) and two major different peaks (3-hydroxypuerarin 5 and 3'-methoxypuerarin 6) in their chromatograms. Semi-quantitative analysis showed that the contents of 1-3 in Pueraria lobata are about three, three, and five times higher than those of Pueraria thomsonii, respectively. The higher contents of isoflavonoids in Pueraria lobata were inferred to be responsible for its more potent antioxidant activity as compared with that of Pueraria thomsonii. The HPLC method developed in this study and chemical markers 1-6 can be used for the rapid identification and evaluation of Radix Puerariae herbs and their aqueous supplements, and the results of this investigation support the use of Pueraria lobata and Pueraria thomsonii in the clinic application and as dietary supplement, respectively.