Daily treatment of ovariectomized (OVX) ICR mice with puerarin, a glycosyl isoflavone isolated from the root bark of Pueraria candollei var. mirifica, and 17β-estradiol attenuated ovariectomy-induced depression-like behavior, as indicated by a decrease in immobility times in the tail suspension test (TST) and the forced swimming test (FST), an increase in the uterine weight and volume, a decrease in serum corticosterone levels, and dose-dependently normalized the downregulated transcription of the brain-derived neurotrophic factor (BDNF) and estrogen receptor (Erβ and Erα) mRNAs. Like 17β-estradiol, puerarin also inhibited ovariectomy-induced suppression of neurogenesis in the dentate gyrus of the hippocampus (increased the number of doublecortin (DCX)-immunosuppressive cells). These results suggest that puerarin exerts antidepressant-like effects in OVX animals, possibly by attenuating the OVX-induced hyperactivation of the HPA axis and/or normalizing the downregulated transcription of BDNF and ER mRNA in the brain.Molecules 2019, 24, 4569 2 of 15 depression. These symptoms can be reversed by supplementation with estrogen. A body of evidence suggests that such estrogen replacement therapy (ERT) can exert anxiolytic and antidepressant effects in menopausal females by modulating the hypothalamic-pituitary-adrenal (HPA) axis functions [3,4]. However, the drawback of ERT is its adverse effects, such as an increased risk of breast and endometrial cancers, as well as thromboembolic events [5,6]. Consequently, the long-term usage of ERT to ameliorate emotional and cognitive deficits has an obvious limitation in women. Thus, the search for new phytoestrogens, with a weak effect on reproductive organs, from natural sources continues to be an important field of research.Pueraria candollei var. mirifica is a medicinal plant used in Thai traditional medicine for its rejuvenating and estrogenic effects [7]. For this reason, this plant has been widely investigated for its constituents and pharmacological activities. Peerakam et al. [8] found that the 95% ethanol extract of this plant contained puerarin (1), as a major compound, and other isoflavonoids, such as daidzin, daidzein, genistin, and genistein, in addition to the phytoestrogens miroestrol and deoxymiroestrol. Suthon et al.[9] evaluated the anti-osteoporotic effects of the crude extract of P. candollei var. mirifica and puerarin (1) in ovariectomized (OVX) mice and found that only the crude extract at 50 mg/kg (body weight) per day caused a significant increase in the trabecular bone mineral densities of tibia metaphysis when compared to the control group. On the other hand, the pharmacological activities of puerarin (1) (Figure 1), a major isoflavonoid from P. candollei var. mirifica, have been extensively investigated. Puerarin (1) has been widely used in the treatment of diabetes, dyslipidemia, liver fibrosis, cardiovascular diseases, neurotoxicity, and Alzheimer's disease [10]. This compound was also found to exhibit various protective effects against fever, hyper...