Chemical Profiling of Pueraria lobata and Pueraria thomsonii using Total Phenolic, Flavonoid, Carbohydrate and Antioxidant Assays

Kudzuvine root (KVR, dried root of Pueraria lobata (Willd.) Ohwi) has long been used in traditional Chinese medicine for the treatment of diabetes and cardiovascular diseases. Thomson kudzuvine root (TKR, dried root of P. thomsonii) is a similar species within the genus Pueraria and is often used interchangeably with or as a substitute for KVR. According to the Chinese Pharmacopoeia, the amount of the major component puerarin in KVR should not be less than 2.4%, whereas in TKR, the puerarin content should not be less than 0.3% [1]. Even though the chemical profiles of these two species are notably different, the recommended dose, indications and actions of both herbs are very similar. The aim of this study is to compare the chemical characteristics of these two species. Ethanolic extracts of KVR and TKR were analyzed by HPLC and various spectrophotometric assays, including total phenolic content (TPC), total flavonoid content (TFC), total carbohydrate content (TCC), ABTS and DPPH radical scavenging capacities and ferric antioxidant reducing power (FRAP). Our preliminary results demonstrate that KVR has significantly greater experimental values in all of the spectrophotometric assays aforementioned (Table 1). The amount of the major constituents, including puerarin, daidzin, daidzein, genistin and fomononetin, in KVR is markedly higher than those in TKR (p<0.001). Such differences in the chemical characteristics between these two species may have significant impact on their corresponding therapeutic effects. Investigation on their detailed molecular mechanisms and a review on their therapeutic doses are warranted in the near future.

Table 1: Comparison of various spectrophotometric assays between Kudzuvine root and Thomson kudzuvine root

a Average values of five samples with triplicate determinations (n=5) b Total phenolic content (g gallic acid equivalent/100g dry mass) c Total flavonoid content (g quercetin equivalent/100g dry mass) d ABTS scavenging capacity (µmol trolox equivalent/g dry mass) e DPPH scavenging capacity (µmol trolox equivalent/g dry mass) f Ferric reducing antioxidant power (µmol iron (II) sulfate equivalent/g dry mass) *significant (p<0.001) between KVR and TKR
	Kudzuvine roota	Thomson kudzuvine roota
TPCb	45.81±1.48 *	28.42±1.34
TFCc	31.65±3.38 *	4.96±1.09
ABTSd	3465±0.06 *	433.2±0.06
DPPHe	156.9±22.86 *	14.57±1.18
FRAPf	1212±56.71 *	218.1±59.80

Reference: [1] Pharmacopoeia of the People's Republic of China. (2005) People's Medical Publishing House, Beijing, 1: 230–231.