Pueraria Mirifica

Pueraria Candollei is a species within the Pueraria genus and the Leguminosae family; a particualr variant of this species known as Mirifica is commonly sold as a supplement. This variant is sometimes simply called Pueraria Mirifica and omits the species name or it is referred to as Kwao Krua (particular 'White' Kwao Krua, as the latter term refers to up ).^[1][2]

Pueraria Mirifica (the word Mirifica being taken from the Latin word 'Miracle') has been used in Thai medicine for the purposes of the rejuvenation of menopausal women; one of three well known rejuvenatory herbs as well as Butea superba and Mucuna collettii (which are two other popular rejuvenators).^[1] Kwao Krua, as Pueraria Mirifica is commonly called alongside the other two aforementioned plants^[3], is a root plant and the tubers are considered the active component^[1] and its estrogenic potential has been noted since 1952.^[4] It is sometimes thought to be anti-aging.^[5]

Pueraria Mirifica is one of three herbs known as Kwao Krua, specifically known as White Kwao Krua ('Red' Kwao Krua is Butea superba while 'Black' Kwao Krua is Mucuna collettii) with all three plants being reported to be anti-aging and vitality promoting herbs for women

The composition of Pueraria Candollei variant Mirifica (Pueraria Mirifica) is:

• The Chromene compounds Miroestrol, a phytoestrogen known to be the primary active ingredient^[6][7][8] as well as both Deoxymiroestrol and Isomiroestrol;^[9][10] the 'main' chromene in name, Miroestrol, is at approximately 0.002% of the plant by dry weight^[11][12]
• The isoflavone Puerarin at 20.25-22.43mg/100g (Puerarin is a glycoside of Genistein^[2]and also found in Psoralea Corylifolia) as well as both soy isoflavones Daidzein (5.73-10.44mg/100g free form and 15.51-23.62mg/100g of the glycoside Daidzin) and Genistein (1.27-2.10mg/100g free form, 38-48.44mg/100g of the glycoside Genistin).^[12][2][13] Estrogenic isoflavones in Pueraria Mirifica including glycosides total 8.4-10.2% dry weight^[14]
• Kwakhurin, a prenylated isoflavone^[15] that has some estrogenic activity (weak relative to the chromenes^[12]) at 0.0064-0.0067% dry weight^[11] or less^[12]
• Puemiricarpene, a pterocarpene^[12]
• Coumestrol^[16]
• Tuberosin^[16]
• Mirificin (diglycoside of Genistein)^[16]
• Spinasterol, also estrogenic^[17]
• Water soluble polysaccharides with an average weight of 27kDa rich in glucose (73%)^[5]

Pueraria Candollei var. Mirifica (Kwao Krua) appears to have a large amount of phytoestrogenic compounds, particularly isoflavones, including the ones known as soy isoflavones; there is also a class of three molecules known as chromenes, and the molecules in this class (Miroestrol, Isomiroestrol, and Deoxymiroestrol) are estrogenic with a similar potency to estrogen itself

Quality control may be important for supplemental White Kwao Krua as the visual properties of the plant are highly similar to other plants of the Pueraria genera, including Pueraria Lobata (Kudzu)^[11] and also very similar looking to 'Red Kwao Krua', Butea Superba (one of the reasons they are both named Kwao Krua is due to them initially thought to be the same plant).^[18] Although the species of Candollei tends to be further refined into the variant Mirifica, both variants of Candollei possess a Miroestrol and Deoxymirostrol content to roughly similar levels (Mirifica was found in this study to have 121.34+/-6.46μg/g total chromenes in the whole tuber while Candollei was found to have 121.41+/-1.68μg/g).^[19] That being said, the exact level of phytoestrogenic bioactives seems to be subject to a high degree of variability depending on cultivar, growing conditions, and plant age^[20] which then influence the estrogenicity.^[21]

There may not be too much of a difference between variants of Pueraria Candollei (Candollei versus Mirifica) despite traditional usage of the latter

An in vitro study assessing the estrogenicity of compounds in Pueraria Mirifica noted that concentrations of the herb between 0.025ng/mL and 2.5mcg/mL failed to induce an estrogenic response yet in an MCF-7 (breast cancer cell) assay a dose-dependent increase was seen with 250-2500ng/mL being as effective as 25nM estradiol while in HepG2 cells it outperformed estradiol.^[22] These results suggest that the estrogenic activity seen with Pueraria Mirifica is not due to a compound found in the herb per se, but due to a cellular metabolite when one of the compounds is subject to metabolism (to form a more potent metabolite than the parent molecule).^[22]

Plant extracts that are known to have such a relationship can be bioactivated in vitro with S9,^[23] which has been used in some studies with Pueraria Mirifica.^[24]

Phytoestrogens may require bioactivation within the cell, which although is not important for supplemental purposes may skew results obtained using yeast assays (whole cell assays, such as MCF-7 and HepG2, are unaffected)

10-50ug/mL of a Pueraria Mirifica extract in hippocampal cells subject to excitotoxic stress induced by glutamate, with 50ug/mL of this extract having similar protective potential as 132ug/mL Trolox (water soluble form of Vitamin E).^[16] The antioxidant potential of this extract, thought to underlie the protective effects, in a DPPH assay was that of having an EC₅₀ value of 0.192mg/mL, which was far less than that of Genistein (13.794mg/mL) and Daidzein (14.257mg/mL) and even the synergistic mixture of the two (7.558mg/mL) suggesting other antioxidant compounds of far greater potency.^[16]

May have neuroprotective properties, practical relevance or significance currently unknown

One study has noted that prolonged incubation with either 17β-estradiol of Pueraria Mirifica in hippocampal neurons increases the concentration of the protein synaptophysin (thought to be indicative of synaptic growth) in a concentration dependent manner up to 60mcg/mL due to acting on the estrogen receptors, as the induction was blocked with an estrogen receptor antagonist.^[25]

Estrogen itself enhances synaptic plasticity in hippocampal cells, the phytoestrogens in Pueraria Mirifica may mimic this

In an open-label trial of 50mg or 100mg Pueraria Mirifica daily for 6 months (no control group) noted that the reduction in menopausal symptoms as assessed by the Green Climactic scale (self-report) was reduced to 42% of baseline in the 50mg group and 100mg as well after 6 months.^[26] This study design was repeated later by the same researchers in perimenopausal women, but still did not introduce a placebo condition and blinding (was again open-label).^[27]

In 52 hysterectomized (without uterus) women who suffered menopausal-like symptoms who were subsequently divided into a 25mg or 50mg group for supplemental Pueraria Mirifica and followed for 6 months, it was noted that both groups were able to reduce climactic scores of menopause at 3 months (74% and 66% of baseline with 25mg and 50mg, respectively) and 6 months (58% and 53% of baseline) with the difference between groups not being significant; this study did not have a placebo condition.^[28]

Currently, the one study that used a blinded protocol also did not use a placebo condition but compared Pueraria Mirifica at 50mg against 0.625mg Conjugated Equine Estrogen (CEE) with 2.5mg medroxyprogesterone acetate (MPA) and noted that there was no significant difference between treatments.^[29]

Numerous trials note reductions in menopausal symptoms that do not appear to be dose-dependent with treatment but appear to be time-dependent (more benefit over time), but a major problem here is that no studies appear to be blinded or use a placebo. In using Black Cohosh as an example, a placebo condition is mandatory for quality results on the topic of menopause and the benefits observed with Pueraria Mirifica could very well be placebo

100mg/kg of the ground powder of Pueraria Mirifica given to New Zealand rabbits for 90 days noted an enhanced vasorelaxant response to acetylcholine (24%), which appeared to be mediated by nitric oxide as the benefit was abolished with the specific nitric oxide inhibitor L-NAME.^[30] This was thought to be related to the estrogenic effects of Pueraria Mirifica as estrogen is known to positively influence nitric oxide-mediated vasorelaxation.^[31][32]

May benefit circulation in a similar manner as estrogen itself, due to estrogen-like signalling via nitric oxide

After 2 months of treatment of Pueraria Mirifica extract to postmenopausal women, the treatment group noted an increase in HDL-C (34%) with a concomitant decrease in LDL-C (17%) which was thought to be secondary to the estrogenic effects of the components.^[33]

One study noted a 15% increase in triglycerides relative to baseline associated with Pueraria Mirifica at 20-50mg daily, but the increase was also observed in placebo and deemed to likely not be related to treatment.^[34]

May also influence lipid metabolism in a similar manner as estrogen, but surprisingly little evidence to support this notion

Specialized cell types called osteoblasts and osteoclasts are responsible for regulating bone growth. While osteoblasts are responsible for bone synthesis, osteoclasts break down bone tissue. Thus, the balance of osteoblast vs. osteoclast activity controls bone homeostasis. When this balance becomes disturbed in diseases such as osteoporosis, osteoclasts become over-active, depleting bone mass and resulting weak, brittle bones that are prone to breakage.

Since studies on phytoestrogens have been shown to have potential positive effects on bone mass by influencing osteoclast and osteoblast activity,^[35] Pueraria Mirifica has been examined as a possible bone-mass modulator. In a recent study primary osteoblast cells isolated from adult baboons were treated with 100μg/ml Pueraria Mirifica extract in vitro.^[36] This increased the rate of cell proliferation and mRNA levels for osteoblast differentiation markers including alkaline phosphatase and type I collagen. Moreover, Pueraria Mirifica extract decreased markers of osteoclast function (RANKL/OPG ratio) suggesting that it may help decrease osteoclast-mediated bone resorption.^[36] While results from this in vitro study need to be validated in vivo, the effects of Pueraria Mirifica extract on bone homeostasis indicate that more studies are warranted to look into possible applications as a treatment for osteoporosis.

In osteoblast-like UMR106 cells, Genistein and Puerarin as well as a mixture of all isoflavones in Pueraria Mirifica was able to concentration dependently increase bone cell differentiation up to 1mcg/mL; a significant upregulation of ALP, RANKL and OPG (biomarkers of bone cell differentiation) was noted although Runx2, osterix and osteocalcin were unaffected.^[37] These effects were abolished with incubation of an estrogen receptor antagonist (ICI182780).^[37]

Possesses mechanisms to promote bone cell differentiation in vitro, possibly mediated via the estrogen receptor

In ovariectomized mice given either 2.5-25mg/kg of Pueraria Mirifica or 0.1-1mg/kg of the main bioactive Miroestrol for 60 days noted that the increase in OPG and decrease in RANKL (two proteins that mediated bone metabolism and are altered in such a way during menopause^[38]) was somewhat restored, with 25mg/kg of the herb being equally effective as the active control (0.1mg/kg Estradiol) while 1mg/kg Miroestrol was equally effective but trended more towards normalization.^[8] Larger oral doses (10-1000mg/kg Pueraria Mirifica in rats) have noted dose-dependent prevention of bone mass losses over 90 days with 100mg/kg being equally effective as 0.1mg/kg 17α-ethinylestradiol (10mg/kg and 1000mg/kg being not significantly different, but trending to be less and more effective respectively);^[39] this study is duplicated in Medline.^[40]

Animal studies support a dose-dependent benefit on bone mass in ovariectomized animals (a research model to mimic menopause)

One human study using 20-50mg of Pueraria Mirifica daily for 24 weeks noted a decrease in serum bone-specific alkaline phosphatase (0.22+/-0.18U/L to 0.13+/-0.01U/L; 41% decrease), suggesting that these pro-skeletal effects are relevant in humans.^[34]

No studies currently assess bone mass, but serum biomarkers thought to represent bone metabolism suggest bone-sparing effects in women taking the standard dose of Pueraria Mirifica

A water soluble polysaccharide from Pueraria Mirifica was able to increase the T-cell expression of CD69 in response to an antigen by 17.1% when at 100mcg/mL; this outperformed the active control of SEB superantigen at 10mcg/mL but underperformed relative to Butea superba (27%).^[5]

Polysaccharides (questionable as to whether they are contained within supplemental capsules, these carbohydrates are usually processed out) may have immune enhancing properties

As assessed by a vaginal cornification assay, Miroestrol (the bioactive component of Pueraria Mirifica) appears to be a quarter as potent as 17β-estradiol in inducing estrogenic like effects.^[41] It has been noted that Deoxymiroestrol is actually stronger than Mirosterol (as well as Isomiroestrol) with about 10-fold greater potency in an MCF-7 cell assay relative to Miroestrol.^[10] These authors suggested that Deoxymiroestrol should be considered the main bioactive estrogen, since it is plausible that passive oxidation by exposure to the air could have resulted in Miroestrol production from Deoxymirosterol.^[10] Relative to the soy isoflavones Genistein and Daidzein, the chromene compounds Miroestrol and Deoxymiroestrol are approximately 1,000-10,000 fold more potent on a weight basis (claim stated here,^[11] which compares the potencies derived from these two studies^[10][12]) and in some studies directly assesing the claim it is found that the soy isoflavones do not contribute towards the majority of estrogenicity.^[42]

These estrogenic effects are noted either in vivo or in vitro tests using MCF-7 or HepG2 cell lines, and are not seen to a large degree with Yeast assays^[22][24] as it appears that the main bioactives (chromenes) may require cellular metabolism into another molecule prior to exerting estrogenic effects.^[22]

There is limited evidence as to what subset of the estrogen receptor Pueraria Mirifica favors, but at least one study has noted a greater signalling potential of the same extract through the ERα rather than ERβ.^[24] The other species, Pueraria Lobata (Kudzu), does not appear to be a potent estrogenic herb although it has some estrognic activity.^[43]

The chromene compounds are potent and direct estrogen receptor agonists, and Deoxymiroesterol appears to be more potent than 17β-Estradiol itself (17β-Estradiol is the most relevant naturally occuring estrogen compound in the human body)

Other components have phytoestrogenic potential, such as Spinasterol which appears to favor ERα over ERβ (with 0.5uM of the fraction containing Spinasterol being as potent as 1uM estradiol on ERα, but no tested concentration able to outperform or match on ERβ).^[17] Genistein and Daidzein are known to possess estrogenic properties, and both Puerarin and Mirificin are glycosides of Genistein. Unless Puerarin is metabolized into Genistein (possibly via intestinal bacteria) the glycoside itself is a fairly weak estrogen.^[44]

The isoflavones, and some other molecules in Pueraria Mirifica, are also phytoestrogens but of lesser potency

Estrogenic effects have been confirmed in primapes following oral administration of Pueraria Mirifica, with 10-100mg of the herb prolonging the menstrual cycle while 1000mg completely abolished it.^[45] Isolated Miroestrol has also been noted to enhance mammogenesis in ovariectomized rats^[46] and has its estrogenicity shown in vaginal cornification assays.^[47]

These estrogenic effects have been noted to occur in vivo following oral ingestion of Pueraria Mirifica

When looking at serum estrogens themselve (estradiol), there is either no influence of unreliable suppression of circulating estrogens which appear to be of greater magnitude with rising doses.^[48] This may be related to negative feedback from estrogen receptor signalling.

In male mice given 10-100mg/kg of Pueraria Mirifica daily for 8 weeks, the lack of toxicity to the testicles oversed was met with a failure to reduce circulating testosterone levels which remained at levels similar to control and to baseline values.^[49]

Limited evidence, but there is currently no evidence to support a reduction in testosterone associated with supplemental Pueraria Mirifica

No significant modifications in Luteinizing Hormone (LH) have been noted with 10-100mg/kg daily Pueraria Mirifica daily in male mice for 8 weeks^[49] although higher doses (1,000mg/kg in rats; human dose of 160mg/kg) are able to suppress Lutenizing Hormone.^[50]

No significant modifications in Follicle Stimulating Hormone (FSH) have been noted with 10-100mg/kg daily Pueraria Mirifica daily in male mice for 8 weeks^[49] although higher doses (1,000mg/kg in rats; human dose of 160mg/kg) are able to suppress FSH.^[50]

A study assessing the serum 30 days prior to and up to 60 days after a treatment period (90 days) in menopausal monkeys noted that 1,000mg of Pueraria Mirifica was able to suppress Parathyroid Hormone during treatment as early as 15 days; both 10mg and 100mg were overall ineffective in reducing PTH despite a trend to do so.^[48] Serum calcium followed similar trends as PTH.^[48]

The anti-oxidative properties of the tubers may be related to the isoflavones Puerarin and Daidzein.^[51]

In rats subject to ovariectomy (to simulate menopause), the decrease of endogenous antioxidant enzymes was attenuated with supplemental Pueraria Mirifica as well as the active component miroestrol (although estradiol per se was ineffective).^[52]

May have anti-oxidant properties; nothing overly remarkable relative to other compounds

In mouse hepatocytes, Deoxymiroestrol exerts similar effects on AhR and ER-dependent gene products as estradiol itself (due to acting vicariously through estrogen receptors)^[53] although it differed as induction of CYP1B1 and Aromatase was synergistically enhanced when the inducing agent (β-naphthoflavone) was incubated with Deoxymiroestrol.^[53]

The bile salt export pump (BSEP) and MRP2 are two proteins which are involved in bile acid efflux from the liver, and 0.5mg/kg of either Miroestrol or Deoxymirosterol has been noted to suppress the mRNA of these two transporters.^[54] The authors noted that this was a mechanism thought to underlie hepatoxicity associated with 17α-Ethynylestradiol (an estrogenic contraceptive)^[55] and the authors hypothesized that this could result in hepatic bile acid accrual and, subsequently, result in intra-hepatic cholestasis.^[54][56]

Theoretically possible that the estrogenic activity of Pueraria chromenes could reduce in some hepatotoxicity via reducing bile acid efflux; currently not demonstrated in a living model, however

Pueraria Mirifica is known to interact with the uterus and female reproductive organs as the first test to establish its estrogenicity was that of a vaginal cornification assay (detection of epithelial cells that express some cornification when taking a urine test)^[41] which has been replicated at 100mg/kg but not 10mg/kg.^[47] An estrogenic effect is noted in vaginal tissue at doses above 100mg/kg in rats to a similar degree as estradiol (although this study also noted that the urethral effects of estradiol were not well mimicked)^[57] and this has been observed at doses as low as 10mg (menopausal cynomolgus monkeys) within 24 hours of oral treatment as assessed by vaginal reddening.^[58]

In female primapes where 90 days of treatment of 10mg or a single dose of 1000mg failed to alter the estrus cycle or related hormones, it was noted that 90 days of 100mg was associated with a reduction in length of the estrus cycle followed by cessation and this was also noted with 1,000mg daily.^[59] This ovulation block has been noted previously by the same research group,^[45] and the single dose of 1,000mg has elsewhere been noted to influence the estrus cycle (altered phase durations, but not cessation).^[60]

In a toxicological test using 10mg/kg or 100mg/kg of Pueraria Mirifica daily for 8 weeks noted that while 10m/kg was without effect both the 100mg/kg group and the active control group (200mcg estrogen diethylstilbestrol) prolonged the length of the estrus cycle; although no toxic effects were noted, 100mg/kg was associated with hyperplasia of the uterine endothelium and a decrease of the ovarian follicle count as well as decreased mating efficiency.^[61]

In rats, 10mg/kg appears to be free of side effects (1.6mg/kg in a converted human dose; for a 120lb woman this equals 87mg and for a 180lb woman this is 131mg) although doses 10-fold higher have estrogenic side-effects on the uterus. High doses of near 1,000mg taken daily may be highly anti-fertility by preventing the estrus cycle from occurring

At least one study in humans using 20-50mg of Pueraria Mirifica daily for 6 months in otherwise healthy postmenopausal women that noted an estrogenic effect on bone tissue (as assessed by serum levels of ALP) failed to find an estrogenic effect on endometrial thickness or histology.^[34] A study directly assessing toxicological studies in humans noted that 20-50mg of Pueraria Mirifica daily for 6 months in menopausal women confirmed estrogenic effects (decreased vaginal dryness and increased vaginal maturation index) without any significant estrogen-related side-effects.^[62]

It appears that the dosage range of 50mg Pueraria Mirifica or below is not associated with toxic effects when taken on a daily basis, although limited evidence exists in humans to support this notion. Supplemental Pueraria Mirifica has once been noted to decrease vaginal dryness, a symptoms of estrogen deficiency (most commonly associated with menopause)

Isolated Miroestrol and Deoxymiroestrol incubated in testes of male mice appear to have similar suppressive effects on enzymes within the steroid synthesis metabolic pathway (17β-HSD1 and CYP19 mRNA, to a lesser degree 3β-HSD and CYP17) while inducing 17β-HSD2 mRNA; the direction of effects and magntiude of effect were similar when comparing the chromenes against estradiol.^[63]

In male mice given Pueraria Mirifica at 10-100mg/kg daily for 8 weeks (against an active control of 200mcg/kg estrogen diesthylstilbestol injections) noted that the 10mg/kg dose was free of adverse effects while the 100mg/kg group was free of most adverse effects aside from a decreased weight of the seminal vesicles and epididymes with decreased sperm motility; the estrogen control impaired all functions and exerted toxic effects to the testes.^[49]

May have similar (in phenotype and potency) anti-androgenic and suppressive effects in the testes as estrogen itself

In an Ames test, it appears that Pueraria (Mirifica and Lobata) do not possess any direct mutagenic effects regardless of whether or not they are bioactivated via S9 (to mimic cellular metabolism), but both were slightly antimutagenic when mutations were induced by either benzo(a)pyrene or 2-(2-furyl)-3-(5-nitro-2-furyl)-acrylamide; lack of mutagenicitiy was seen with 300mg/kg oral ingestion in rats^[64] although another study in male mice using higher doses of a water extract (600-800mg/kg, human equivalent dose of 96-128mg/kg) was able to induce a higher frequency of micronuclei formation, indicative of mutagenicity; this was significantly attenuated by coingestion of Thunbergia laurifolia in either a 7:3 ratio (in favor of Pueraria) or a 1:1 ratio.^[65]

Low doses appear to be non-mutagenic, but at least one study noted that mutagenesis can be forced with exceedingly high doses of oral Pueraria Mirifica

Mechanistically, a nonstandard component of Pueraria Mirifica is able to concentration-dependently induce apoptosis in MCF-7, T47D, SK-BR-3, HS578T and MDA-MB-231 (but not ZR-75-1) breast cancer cells; it was noted to be isolated in a specific subfraction (ethanolic extract twice filtered, then extracted with hexane and ethyl acetate) which had an IC₅₀ value in reducing MDA-MB-231 proliferation of 6uM.^[17] Spinasterol may be the active component (an isomer of stigmasterol found in the fraction), although this was not confirmed.^[17]

In rats who consumed 1g/kg of Pueraria Mirifica daily for 4 weeks prior to induction of breast tumors with 7,12-DMBA, it was noted that over the next 20 weeks of observation that rats pretreated with Pueraria Mirifica (relative to control) was associated with a reduced tumor volume, weight, and count by 52.75%, 43.50%, and 50% without significantly influencing tumor metastasis or spreading throughout the body.^[66] THis study noted that tumors excised from the rats had dose-dependently less expression of the estrogen receptors ERα and ERβ, and that the ratio of the two receptor subsets was reduced from 0.83+/-0.04 to 0.42+/-0.02 in favor of ERβ.^[66]

In human interventions, doses up to 50mg have been used in interventions with no significant reported side-effects^[34][29] and doses in the range of 25-100mg in open-label studies lasting up to 6 months have failed to show any relevant toxic effects.^[26][27]

Currently no significant side-effects associated with supplemental Pueraria Mirifica at the standard supplemental dosages

This does not mean Pueraria Mirifica is wholly safe, as its potency and mechanisms suggest that it carries the same risks and benefits as estrogen replacement therapy (these are currently not studied as it pertains to Pueraria Mirifica)