Evaluation of the Estrogenic Activity of Pueraria (Kudzu) Flower Extract and Its Major Isoflavones Using ER-Binding and Uterotrophic Bioassays

Abstract

Pueraria flower extract (PFE) is a hot water extract of the Kudzu flower (Pueraria thomsonii). Tea made from driedKudzu flower is widely used in China, and PFE is utilized as a nutritional supplement in Japan. PFE contains unique isoflavones such as 6-hydroxygenistein 6,7-di-O-glucoside (6HGDG), tectorigenin 7-O-xylosylglucoside (TGXG), and tectoridin. 6HGDG is known to be metabolized into 6-hydroxygenistein, and TGXG and tectoridin are known to be metabolized into tectorigenin in the digestive tract. Isoflavones typically mimic the effects β-estradiol has on estrogen receptors (ERs) and may influence the female genital system in the case of excessive intake. As a result, the upper limit of safe daily consumption of soy isoflavones has been enforced in Japan. In the present study, ER-binding assays were performed using the EnBio estrogen receptor/cofactor assay system to compare the estrogenic activity of 6-hydroxygenistein and tectorigenin to that of the soy isoflavone genistein. In addition, uterotrophic bioassays were performed to investigate the estrogenic effects of PFE in vivo. The ER-binding assays revealed that the ER-binding affinities of 6-hydroxygenistein and tectorigenin were approximately 0.01 -0.04 that of genistein. Soy isoflavone products also induced an increase in uterine wet and blotted weight at doses of 500 mg/kg and 1000 mg/kg, whereas PFE did not cause adverse estrogenic effects, even at a dose of 1000 mg/kg. Based on these results, PFE does not appear to contain compounds with strong estrogenic activity or cause adverse estrogenic effects in vivo. Importantly, the results of this study confirm the safety of PFE as a food supplement.

Assessment of safety and efficacy of pine bark extract in normal and ovariectomized mice

“…Our results showed that PBE did not increased uterine‐weight in OVX mice. Uterine weight gain indicates an excess intake of estrogenic compounds, as observed when dietary supplements containing estrogenic compounds (soy isoflavones 1,000 mg/kg body weight) were ingested by female mice (Kamiya, Takano, Kido, & Matsuzaka, 2013). The administration of Pueraria mirifica (660 mg/kg BW/day) has been reported that pronounced inflammation of the uterine wall and increase in mammary adenocarcinoma incidence in postpubertal rats.…”

Safety and Efficacy Assessment of Isoflavones from Pueraria (Kudzu) Flower Extract in Ovariectomised Mice: A Comparison with Soy Isoflavones

“…Uterine weight in the SI20 treatment group was higher than in OVX mice, but was still lower than in the sham mice (Table 2). Kamiya et al reported that SI products induced an increase in uterine weight at doses of 500 mg/kg in OVX rats, whereas the kudzu flower extract did not cause it, and the ER-binding affinity of the related compound tectorigenin was approximately 0.02–0.04 that of genistein in vitro [17]. Moreover, our study demonstrated that the femoral BMD and trabecular BMD of the distal femur were higher in OVX mice in the SI20 treatment relative to untreated OVX mice, and that the BMDs of mice in the PFI20 treatment did not exhibit a similar response.…”

“…Kudzu flower extract, primarily derived from Pueraria thomsonii , contains isoflavones. Isoflavones induce weak oestrogen-like effects and are classified as phytoestrogens [17]. Thus, kudzu flower extract might be used as an alternative to oestrogen-based menopausal therapies by menopausal women, who are likely to take it concomitantly with other medicines.…”

Efficacy of Non-Soy Isoflavone (Pueraria phaseoloides) on The Symptoms Severity Scoring by Kupperman Index in Menopausal Women

“…Phytoestrogens, specifically isoflavones, are plants considered chemoprotective, with estrogen-like properties compounds, due to their conformational similarity to -estradiol, and can be used as an alternative therapy for hormonal disorders [4,5]. Isoflavones are phenols that enable the activation of estrogen receptors (ER) and the regulation of gene expression in target tissue cell nuclei.…”