IngredientsFormononetin (FMN) is a well-known flavonoid with the parent structure of isoflavones, also known as 7-hydroxy-4′-methoxy isoflavone, with the molecular formula C16H12O4 and a relative molecular weight of 268.26. Its full IUPAC name is 7-hydroxy-3-(4-methoxyphenyl)chromen-4-one. The compound belongs to the subclass of O-methylated isoflavones: formononetin is an O-methylated isoflavone that, along with other phytoestrogens, predominantly occurs in leguminous plants and Fabaceae, particularly in beans such as green beans, lima beans, soy, and many others, as the free aglycone or in the form of its glucoside ononin. Ononin is the 7-O-β-D-glucopyranoside of formononetin.
Formononetin — 7-hydroxy-3(4-methoxyphenyl)chromone — is the major compound of Astragalus membranaceus and Astragalus mongholicus root, but it can also be found in leaves and flowers of Trifolium pratense, roots of Glycyrrhiza glabra and Glycyrrhiza uralensis, and in the root of kudzu (Pueraria lobata). Additional botanical sources include Sophora flavescens, Pycnanthus angolensis, and Glycine max. Beyond medicinal herbs, this isoflavonoid can also occur in dietary products such as beans, carrot, cauliflower, green peas, iceberg lettuce, and red potatoes.
Formononetin is quantitatively significant in red clover. Comparative analysis of red clover samples has found that formononetin is the most abundant of the nine quality control markers measured, ranking above ononin, biochanin A, genistin, daidzin, calycosin-7-O-β-d-glucoside, genistein, daidzein, and chlorogenic acid.
In leguminous plants, formononetin is an important intermediate for the biosynthesis of phytoalexins, which function to defend the plant from stressful environments or diseases. It is mainly synthesized from 2,7,4-trihydroxy-isoflavone by the enzyme 2,7,4′-trihydroxyisoflavanone 4′-O-methyltransferases (HI4′OMTs).
Formononetin is commercially available in the following forms:
Formononetin is not typically extracted and used in isolation in traditional practice; rather, it is a bioactive constituent of herbs with long records of use. Astragalus membranaceus — known as Huangqi — was originally described in Shennong's Classic of Materia Medica, the earliest complete pharmacopoeia of China written from the Warring States Period to the Han Dynasty, and has been widely used in Chinese medicine for more than 2,000 years, especially in prescriptions for treating cancer. Li Shizhen's "Compendium of the Materia Medica" (Ming Dynasty, AD 1552–1578) lists Huangqi as the first tonic herb, primarily used to reinforce healthy qi, dispel pathogenic factors, promote diuresis, and reduce swelling. Huangqi has been prevalent for more than 2,000 years with over 200 types of herbal decoctions and has experienced extensive clinical application in Chinese medicine.
Formononetin is a secondary metabolite of flavonoids abundant in legumes and graminaceous plants such as Astragalus mongholicus Bunge and Avena sativa. Astragalus has been traditionally used in Asian countries such as China, Korea, and Mongolia to treat inflammatory diseases, immune disorders, and cancers.
To date, more than 200 compounds have been isolated from Astragalus species, among which isoflavones such as calycosin, calycosin-7-glucoside, formononetin, and ononin have significant value because of their significant antioxidant, anticancer, anti-inflammatory, and neuroprotective pharmacological effects.
The red clover (Trifolium pratense, family Fabaceae) is a legume known for its numerous health benefits and can hold a crucial role in the prevention and management of certain health conditions, including type 2 diabetes, hyperlipidemia, and hypertension. It is a perennial herb commonly found in Asia, Europe, and North America, and has been traditionally used to treat skin and respiratory conditions such as eczema, psoriasis, asthma, and pertussis. The extract of T. pratense has been used as an expectorant, analgesic, anticoagulant, antiseptic, and febrifuge agent in traditional medicine.
The products of red clover are also used as dietary supplementation to relieve women's menopausal symptoms. The isoflavones present in red clover have estrogen-like activities and have been subjected to intense research over the past two decades due to their potential cancer-preventive, cardio-protective, and anti-osteoporosis effects.
It has been known for many years that dietary isoflavonoids can exert estrogenic effects in animals. Reports as early as 1946 documented the occurrence of infertility in sheep resulting from grazing on clover rich in the isoflavone formononetin, and breeding programs have been devised to select for low isoflavone lines of subterranean clover. These early observations established the phytoestrogenic character of the compound and drew scientific attention to its biological activity.
Isoflavones, a unique large class of flavonoids mainly found in soybeans and legumes, have estrogenic activity and can bind with estrogen receptors. Phytoestrogens are not hormones in the traditional sense but are secondary metabolites of plants. They are similar to animal estrogen in structure and function and can have many effects on health, which may help to prevent certain hormone-related diseases such as breast cancer and osteoporosis.
Given that the structure of formononetin is relatively similar to endogenous oestrogen (estradiol), formononetin is known to be one of the phytoestrogens able to bind to oestrogen receptors, namely estrogen receptors α and β. Formononetin is suggested to be a natural selective estrogen receptor modulator (SERM). SERMs such as raloxifene reveal estrogenic activity in bone cells, thereby inhibiting osteoporosis development in postmenopausal women, without uterotropic and mammotropic effects.
By interacting with key inflammatory signaling pathways (NF-κB, MAPK, JAK-STAT, PI3K-AKT, and TLRs) and through estrogen-dependent mechanisms, formononetin exerts strong anti-inflammatory effects that contribute to its overall health benefits. Formononetin has antioxidant and anti-inflammatory potential and shows mild or no toxicity in various diseases.
In vitro studies based on different human cancer cell lines provide deeper insights into novel molecular and cellular mechanisms of formononetin that impede the progress of carcinogenesis and metastasis. The notable mechanisms include regulation of transcription factors, modulation of epigenetic targets, regulation of estrogen receptors, and regulation of cell cycle, induction of apoptosis.
Formononetin fights the progression of cancer via inducing apoptosis, arresting the cell cycle, and halting metastasis by targeting various pathways that are generally modulated in several cancers.
Studies have found that formononetin significantly reduces infarct volume and brain water content, improves neurological deficits, upregulates ER-α and p-Akt, and downregulates the Bax/Bcl-2 ratio in ischemia/reperfusion models. Formononetin's neuroprotective effects on cerebral I/R injury may be associated with the downregulation of the Bax/Bcl-2 ratio and the activation of the PI3K/Akt signaling pathway.
A number of studies have shown that formononetin, as an isoflavone and phytoestrogen that displays pro-angiogenic effects, could promote vascular recovery by regulating endothelial cell proliferation and migration at sites of vascular injury. Results from human umbilical vein endothelial cells (HUVEC) using real-time migration systems, immunofluorescence, and Western blotting provided strong evidence of formononetin-induced endothelial cell migration and dramatic actin cytoskeleton spatial modification through ERα-enhanced ROCK-II/MMP2/9 signaling pathways. Co-immunoprecipitation results suggested formononetin induces cell migration via recruiting of ERα/ROCK-II activated complex formation.
Results of KEGG pathway assays indicated that many targets were enriched in PPAR signaling. Formononetin protects against oxidized-LDL-induced inflammatory reaction, oxidative stress, and apoptosis in HUVECs, and attenuates ox-LDL-mediated inactivation of PPAR-γ signaling.
Formononetin belongs to the isoflavones and has estrogen-like effects. It can promote osteoblast differentiation by activating the p38 MAPK/Smad/bone morphogenetic protein (BMP) signaling pathway.
Formononetin is metabolized into the bioactive compound daidzein (DZN) by gut microflora and cytochrome P450 isoforms 1A2, 2C9*1, 2A6, and 2C19. Daidzein is further converted into two other bioactive compounds — dihydrodaidzein (DHD) and equol (EQL). Gut microbiota play a significant role in biotransformation and degradation of isoflavones in humans. Given that the composition of gut microbiota differs considerably between individuals, the highly variable process of biotransformation mediated by gut microbiota could have a substantial impact on plasma concentrations of formononetin and its metabolites, subsequently leading to differential biological effects.
Formononetin is a key constituent of red clover isoflavone extracts (e.g., Promensil, Rimostil) that have been the subject of clinical trials focused on menopausal vasomotor symptoms (VMS). Bioactive isoflavones from red clover, particularly biochanin A and formononetin, show promise as candidates for treatment of menopause symptoms, as recent clinical trials have demonstrated beneficial effects against menopausal VMS and show minimal side effects with treatment. The safety profile of these compounds is promising and has been tested in numerous human trials.
A significant clinical trial published in PLOS ONE examined combined red clover isoflavones (containing formononetin) with probiotics, finding potent reductions in menopausal vasomotor symptoms. The possibility that heightened cardiovascular risk associated with menopause can be reduced by increasing dietary isoflavone intake was tested in 17 women by measuring arterial compliance, an index of the elasticity of large arteries such as the thoracic aorta. Compliance diminishes with age and menopause. An initial 3- to 4-week run-in period and a 5-week placebo period were followed by two 5-week periods of active treatment with 40 mg and then 80 mg isoflavones derived from red clover containing genistein, daidzein, biochanin, and formononetin.
Evidence strength: Moderate. Most clinical trials assess red clover extracts (which include formononetin among several isoflavones), not formononetin as an isolated compound. There is a wealth of information on formononetin's anticancer effects in vitro and in animals, but no clinical investigations have been conducted specifically on the isolated compound. Clinical trials of formononetin continue; clinical trials were conducted to investigate the effects of formononetin — the most prevalent type of red clover isoflavone — on postmenopausal urinary microbiota composition and interactions with the urothelium (ClinicalTrials.gov Identifier: NCT05013593).
Osteoporosis is a common clinical pathologic bone disease, resulting from the imbalance between the functions of osteoblasts and osteoclasts, most common in the elderly and postmenopausal women. Estrogen levels decline in postmenopausal women, leading to disruptions in osteoblast differentiation and activation, reduced synthesis and deposition of new bone, and ultimately osteoporosis.
In a key animal study, twelve-week-old female rats were divided into four groups: sham-operated, ovariectomized, ovariectomized treated with estradiol (0.2 mg/kg), and ovariectomized treated with formononetin (10 mg/kg), with substances administered orally for four weeks. Supplementation with formononetin resulted in slightly enhanced bone mechanical properties and bone chemistry improvement (significantly lower water content and insignificantly higher mineral fraction content). Administration of formononetin to ovariectomized rats shows a beneficial effect on bone biomechanical features and chemistry, suggesting it can prevent osteoporosis development.
A separate PubMed-indexed study concluded: daily oral administration of formononetin for 12 weeks has a substantial anabolic effect, thus raising the possibility of its use in postmenopausal osteoporosis.
Research on bone healing in a mouse model found that μCT analysis showed that formononetin promoted bone healing at days 10 and 21, with the healing effect significantly better than in ovariectomized mice and equal to PTH treatment in many aspects. Formononetin also significantly enhanced bone regeneration as assessed by calcein-labelling studies and enhanced the expression of osteogenic markers at the injury site in a manner similar to PTH.
In vitro studies have shown modulation of osteoblastic functions, and in vivo studies have indicated the acquisition of bone mass peaks in growing rats, which may be usable in the future as therapy for menopausal osteoporosis.
Evidence strength: Preclinical only for formononetin as an isolated compound. Publications about the effects of other phytoestrogens — such as biochanin A, daidzein, or formononetin — on bone microarchitecture, biomechanical properties, and chemical composition are still scarce, and no controlled human clinical trials have specifically evaluated isolated formononetin for osteoporosis. The bone outcomes observed in red clover extract trials are largely attributed to the overall isoflavone mixture.
Animal and in vitro research has shown formononetin's cardioprotective potential. As a principal isoflavone compound extracted from Radix Astragali, formononetin has been reported to have numerous pharmacological properties, including anticancer, anti-inflammatory, antioxidant, antiviral, neuroprotective activity, and wound healing. Considering that autophagy has been proven to protect myocardial cells from ischemia/reperfusion (I/R) injury, formononetin may protect aged myocardial cells from I/R damage by regulating autophagy.
Clinical trials using red clover isoflavone extracts (containing formononetin along with biochanin A, genistein, and daidzein) have produced mixed results. Studies examining red clover isoflavones and lipid homeostasis have conflicting results and are compromised by differing isoflavone compositions, inadequate blinding or randomization, lack of a control group, and poor completion records. In one trial, three doses of a red clover extract (Rimostil: 28.5 mg, 57 mg, and 85.5 mg daily) were administered to 46 postmenopausal women for six months in a double-blind protocol. Non-fasting measurements showed a significant rise in HDL of 15.7–28.6% and a decrease in apolipoprotein B of 11.5–17% after six months. However, no significant changes were noted in total cholesterol, HDL, LDL, or triglycerides in at least one other trial; and in a single-blind randomized crossover trial with 14 of 21 premenopausal women using 86 mg red clover extract, no alteration in total cholesterol, triglycerides, or LDL oxidizability was identified.
Evidence strength: Weak to moderate, and specific to red clover extracts rather than isolated formononetin. Human trials are inconsistent, and effects cannot be definitively attributed to formononetin alone.
Formononetin has been under intense investigation for the past decade, as strong evidence of promoting apoptosis and inhibiting proliferation suggests its use as an anticancer agent against diverse cancers. These anticancer properties are observed in multiple cancer cell models, including breast, colorectal, and prostate cancer. Formononetin also attenuates metastasis and tumor growth in various in vivo studies.
Studies show that formononetin suppressed cell proliferation through sub G0/G1 phase arrest and increased apoptosis in ovarian cancer cell lines. Furthermore, it induced loss of mitochondrial membrane potential and generation of reactive oxygen species in cancer cells.
An important caveat is that two studies suggested a potential cancer-promoting effect of formononetin at low concentrations (below 6 μM). Formononetin was reported to stimulate proliferation of nasopharyngeal CNE2 cells at 0.3 μM by activating ERK1/2 signaling. Another study reported that formononetin at 1–6 μM stimulated proliferation of estrogen receptor alpha (ERα)-positive breast cancer cell lines (MCF-7 and BT474) but did not affect the proliferation of ERα-negative breast cancer cells (MDA-MB-231).
A Phase IV trial has studied the impact of phytoestrogens from red clover on postmenopausal serum lipids, and a red clover extract (Promensil) Phase II clinical study was completed in surgically treated premenopausal ESR-positive breast cancer patients on tamoxifen.
Evidence strength: Entirely preclinical for formononetin as an isolated compound. There is a wealth of information on formononetin anticancer effects in vitro and in animals, but no clinical investigations have been conducted specifically with isolated formononetin. The data from cell lines and animal models cannot be extrapolated to clinical outcomes in humans.
The neuroprotective properties of formononetin are observed in multiple neurological disorders including Alzheimer's disease, dementia, cerebral ischemia, traumatic brain injury, anxiety, and depression. The beneficial effects are achieved partially through attenuating neuroinflammation and oxidative stress via related signaling pathways.
Formononetin can significantly reduce the level of inflammatory factors, increase the number of dendritic spines in neurons, and increase the expression of βIII-tubulin, growth-associated protein 43 (GAP-43), nerve growth factor (NGF), and BDNF. Formononetin could protect the neurological dysfunction and pathological changes of brain tissue in rats with arterial occlusion from both anti-inflammatory and neuroprotective aspects.
Evidence strength: Preclinical only. Despite its evident effects in numerous preclinical studies, the definite role of formononetin on humans is still less known. No human clinical trials specifically testing formononetin for neurological conditions have been completed and reported.
In the medical field, formononetin has shown potential in the prevention and treatment of cancers, neurological diseases, fibrotic diseases, allergic diseases, metabolic diseases, cardiovascular diseases, gastrointestinal diseases, and autoimmune diseases. These findings come predominantly from in vitro and animal studies reviewed between 2013 and 2023.
Formononetin is one of the phytoestrogens that functions as a selective estrogen receptor modulator (SERM). One study evaluated the effects of formononetin on endometriosis progression both in vitro and in vivo. Phytoestrogens can offer anti-proliferative, anti-inflammatory, antioxidant, and analgesic properties. Specifically, formononetin has been shown to have anti-tumor effects such as anti-proliferative, apoptosis-inducing, anti-cell migration, and anti-invasion effects on breast, prostate, colon, nasopharyngeal, and lung cancer cells in vitro.
Evidence strength: Preliminary, in vitro and animal models only. No human clinical trial data on formononetin specifically for endometriosis is available.
Based on the available peer-reviewed literature, formononetin has been investigated in preclinical and/or (for red clover extracts) clinical settings across the following systems:
The oral bioavailability of formononetin and ononin were 21.8% and 7.3%, respectively. Ononin was more bioavailable than perceived; its bioavailability reached 21.7% when its metabolite formononetin was taken into account. Pharmacokinetic studies have shown that formononetin exhibits oral bioavailability of approximately 20–22% and a half-life of 2–4 hours in rodents, primarily absorbed via passive diffusion and subject to rapid Phase II metabolism through UGT and CYP enzymes.
Plasma protein binding studies revealed plasma binding levels of 93.61 ± 0.44% and 96.14 ± 0.15% at concentrations of 50 ng/mL and 150 ng/mL, respectively. The high degree of protein binding limits the free fraction of formononetin available for tissue distribution.
Due to formononetin's low bioavailability and water solubility, its pharmaceutical use has been limited so far. Several attempts have been made to overcome this physicochemical limitation through formulation development, including poly(lactic-co-glycolic acid) nanoparticles and hydroxypropyl-β-cyclodextrin complexes.
Dosages vary widely between study types and are not established in humans for isolated formononetin:
Formononetin has antioxidant and anti-inflammatory potential and shows mild or no toxicity in various diseases based on the reviewed preclinical literature. Studies carried out to date suggest the lack of any notable side effects or toxic effects with formononetin treatment. A 90-day subchronic toxicity study on sodium formononetin-3-sulphonate (a water-soluble derivative) was evaluated in dogs at various doses. No mortality or abnormalities in body weight, clinical chemistry, haematology, or histopathological examination were detected. Slight toxicity was observed at a 300 mg/kg dose, but the compound was safe up to a 100 mg/kg dose.
Comprehensive toxicological evaluations to establish long-term safety in diverse patient populations are warranted. Although Trifolium pratense extracts (containing formononetin) demonstrate a favorable short- and medium-term safety profile, long-term (greater than 3 years) safety data remain limited.
As opposed to the results obtained in the estradiol-receiving group, administration of formononetin to ovariectomized rats did not affect body mass gain or uterus mass. No uterotropic effect after administration of formononetin was observed in studies where this isoflavone was administered to ovariectomized rats at doses of 0.1, 1.0, and 10 mg/kg intraperitoneally. However, uterotropic effects in ovariectomized mice can be observed when formononetin is administered in higher doses.
The dual agonist/antagonist profile is a critical concern in oncology: formononetin at 1–6 μM stimulated proliferation of estrogen receptor alpha (ERα)-positive breast cancer cell lines (MCF-7 and BT474) but did not affect the proliferation of ERα-negative breast cancer cells. This suggests that formononetin-containing preparations are potentially contraindicated in individuals with hormone-sensitive malignancies, though no human clinical data yet confirm this concern for isolated formononetin.
Given red clover's oestrogenic activity and common concurrent use with conventional pharmacotherapies — particularly among peri- and postmenopausal women — concerns have emerged regarding its potential to alter drug metabolism via the cytochrome P450 (CYP) enzyme system. In vitro assays indicate that T. pratense constituents can inhibit CYP1A1/1A2 and CYP1B1. Care should be taken when administering the extract with other CYP450-interacting compounds, particularly those with a low therapeutic index.
Gut microbiota play a significant role in the biotransformation and degradation of isoflavones in humans. Given that the composition of gut microbiota differs considerably between individuals, the highly variable process of biotransformation mediated by gut microbiota could have a substantial impact on plasma concentrations of formononetin and its metabolites, subsequently leading to differential biological effects.
Red clover is contraindicated in patients with hormonal disorders, estrogen-dependent breast cancer (or risk of), and during pregnancy or lactation. As formononetin is a principal isoflavone in red clover and shares estrogenic mechanisms, these contraindications apply by extension to formononetin-containing preparations.
More research should be performed to verify the anticancer properties of formononetin, with special attention given to the minimum effective dose and its toxicity, in order to provide deeper understanding of the role of formononetin in chemoprevention. Additionally, comprehensive toxicological evaluations to establish long-term safety in diverse patient populations are warranted.
Health conditions that Formononetin may help support.
Formononetin is a methoxylated isoflavone found in red clover and licorice that serves as a prodrug, metabolized by gut bacteria to daidzein and subsequently to equol in some individuals. It binds ERβ and functions as a phytoestrogen, contributing to estrogen balance via selective ER modulation.
Formononetin is a methoxylated isoflavone found primarily in red clover, serving as a metabolic precursor to daidzein. As a major constituent of red clover isoflavone preparations that have demonstrated statistically significant hot flash reductions in meta-analysis (−1.73/day vs. placebo), it contributes to the phytoestrogenic activity of clinically validated red clover extracts.
Formononetin is a methoxylated isoflavone found primarily in red clover and alfalfa that is metabolized to daidzein and equol in the body. Red clover-derived formononetin-containing extracts have demonstrated reduced lumbar bone loss in postmenopausal women in a placebo-controlled RCT. It has estrogenic activity at ERβ receptors in bone tissue.
Formononetin is a phytoestrogenic isoflavone found primarily in red clover and some legumes. It is a precursor to daidzein and has anti-androgenic, anti-inflammatory, and insulin-sensitizing properties documented in preclinical PCOS models and emerging clinical evidence.
Body systems that Formononetin may help support.
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