Phytoestrogens: Chemistry, potential health benefits, and their medicinal importance

Phytoestrogens, also known as xenoestrogens, are secondary metabolites derived from plants that have similar structures and biological effects as human estrogens. These compounds do not directly affect biological functions but can act as agonists or antagonists depending on the level of endogenous estrogen in the body. Phytoestrogens may have an epigenetic mechanism of action independent of estrogen receptors. These compounds are found in more than 300 plant species and are synthesized through the phenylpropanoid pathway, with specific enzymes leading to various chemical structures. Phytoestrogens, primarily phenolic compounds, include isoflavonoids, flavonoids, stilbenes, and lignans. Extensive research in animals and humans has demonstrated the protective effects of phytoestrogens on estrogen‐dependent diseases. Clinical trials have also shown their potential benefits in conditions such as osteoporosis, Parkinson's disease, and certain types of cancer. This review provides a concise overview of phytoestrogen classification, chemical diversity, and biosynthesis and discusses the potential therapeutic effects of phytoestrogens, as well as their preclinical and clinical development.


| INTRODUCTION
Estrogens are hormones that play crucial roles in the reproductive system of women and participate in various processes in both females and males (Cui et al., 2013).These hormones undergo notable changes during different stages of life, such as puberty, pregnancy, or menopause/andropause. Phytoestrogens, which are natural nonsteroidal polyphenolic compounds present in plants, can imitate the actions of estrogens and provide beneficial effects.The primary types of phytoestrogens are lignans and isoflavones, which offer advantages for both women and men (Dixon, 2004).Phytoestrogens, a significant group of plant compounds, are synthesized through the phenylpropanoid pathway.They are subsequently transformed into diverse chemical structures through specific enzymes (Ionescu et al., 2021).These plant molecules, with their distinct structural features, can interact with estrogenic receptors, contributing to the wide range of phytoestrogens.The main categories of phytoestrogens include isoflavonoids, flavonoids, chalcones, flavanones, stilbenes, and lignans (Dixon, 2004).Isoflavones and lignans are major classes of compounds that are widely found in plants.These compounds have various functions, including defensive mechanisms against microbial attack, chemoattraction signals from pathogens, and signals for the initiation of hypertensive cell death (Graham, 1999).Investion of important phytoestrogens has been reported in commercially available lucerne cultivars, in which particular phytoestrogen contents vary between 66.5 and 333.8 mg kg À1 dry matter (Wyse et al., 2021).One study determined that at multiple phases of maturity, Medicago sativa L. develops entire herbage containing individual phytoestrogen concentrations ranging from 15 to 225 μg.g À1 of dry matter (Seguin et al., 2004).Phytoestrogens exhibit structural similarities with the endogen estradiol and thus can interact with the alpha and beta receptors of estrogen (Paterni et al., 2014).Phytoestrogens can have an immediate effect when consumed through food or by undergoing biotransformation in the gut.Biotransformed active metabolites such as urolithins, equals, and enterolignans are derived from ellagitannins, isoflavones, and lignans, respectively (Landete et al., 2016).Different types of phytoestrogens have shown potential beneficial effects on various disease conditions, such as osteoporosis, cardiovascular disease, brain disease, prostate cancer, uterine cancer, and vasomotor symptoms (Graham, 1999;Landete et al., 2016;Paterni et al., 2014;Sirotkin & Harrath, 2014).Clinical trials have generally indicated no serious side effects of phytoestrogen treatments.In this review, we provide a detailed overview of phytoestrogen classification, chemical characteristics and biosynthesis pathways, and the beneficial role of phytoestrogens, as well as preclinical and clinical developments in this field.

| CHEMISTRY OF PHYTOESTROGENS
Phytoestrogens are plant-derived secondary metabolites also known as dietary estrogens and xenoestrogens.Phytoestrogens contain a wide variety of chemical scaffolds, such as isoflavonoids, flavonoids, chalcones, flavanones, stilbenes, and lignans, where isoflavonoids are most significant (Cos et al., 2003;Murkies et al., 1998).Phytoestrogens can be classified into various important classes, as shown in Figure 1.
Chemically, phytoestrogens are nonsteroidal phenolic structures of plant origin that are flavonoids and related phenolic and polyphenolic compounds.The general structures of the phytoestrogens are presented in Figure 2.

| Isoflavonoids
Isoflavonoids are a massive class of plant secondary metabolites that play critical roles in plant defense systems and health benefits for animals and humans and are involved in various activities (Dixon & Sumner, 2003).They are usually regarded as dietary antioxidants that provide protection against oxidative stress, and preventing the risk of macromolecule damage may occur through free radicals and oxidants (Miadoková, 2009).Isoflavonoids, especially those found in the Leguminosae family, are biosynthesized through the central phenylpropanoid pathway and legume-specific isoflavonoid branch.The biosynthesis of these enzymes has been investigated extensively, with nearly all the enzymes isolated and functionally characterized (Figure 3) (Dixon et al., 1995;Winkel-Shirley, 2001).Daidzein and genistein are the principal isoflavones and are aglycones produced from the inactive glycosides daidzein and genistein and from formononetin and biochanin A. Genistein is widely distributed in the Fabaceae family and was first isolated from the Genista tinctoria brooming plant (Sharifi-Rad et al., 2021).Coumestans are a unique subclass of isoflavonoids characterized by the addition of an oxygen-containing four-membered heterocyclic ring system.Sharing a double bond between a benzofuran moiety and a coumarin moiety can be considered the oxidation product of pterocarpan (Tuskaev, 2013).Free radical the ability of coumestans to trap gases via hydrogen transfer in gas media or in the nonpolar phase, while proton loss electron transfer occurs in biological conditions where hydroxy groups, solvents and noncovalent interactions lead to free-radical scavenging (Chen et al., 2023).Coumestans exhibit many pharmacological effects, and four structures, coumestrol, psoralidin, wedelolactone, and glycyrol, are most preferred for drug development against a variety of diseases (Figure 3) (Nehybova et al., 2014;Tu et al., 2021).Ohta et al. reported that the quantity of sprouted soybeans was 1.76 ± 0.13 μg/g, and the F I G U R E 1 A clear classification scheme outlining the various types of phytoestrogens is shown, providing a concise overview of their categorization.
content of sprouted soybeans depended on the temperature (Ohta et al., 2021).HPLC and visible spectroscopic methods are highly established for the identification of isoflavones.(Holmbom et al., 2003) 13 C NMR spectral data of various flavonoids and isoflavonoids have been well established, where data reported for ring A and carbonyl carbons are seldom affected by the location of the ring B connection (Wenkert & Gottlieb, 1977).

| Flavonoids
Flavonoids are polyphenols that are synthesized only in plants such as tea and ginger roots (Savic et al., 2013).Plants are known to biosynthesize flavonoids, which are chemically hydroxylated phenolic compounds, in response to microbial infection (Meister, 2009).There is concern that flavonoids can serve as UV filters and protect plants against radiation since they absorb light in the ultraviolet region of the spectrum (Ferreyra et al., 2021;Stapleton & Walbot, 1994).The biological effects of flavonoids depend on structural features such as structural class, level of polymerization, number of hydroxy groups, conjugations, and presence of various substituents (Heim et al., 2002).
More than 8000 flavonoid structures have been identified from the plant kingdom (Alseekh et al., 2020).Chalcones with cleaved ether rings are also considered to be members of the flavonoid family of plant polyphenolics (Panche et al., 2016).
A class of flavonoids known as flavones are based on their structural component, 2-phenyl-1-benzopyran-4-one.The 13 C NMR spectrum of apigenin, shown with the lowest frequency of carbonyl carbon C-4, needs to be in the lowest range.The aromatics C-2, C-5, C-7, and C-9 are anticipated to be the least shielded at δ values between 150 and 170 due to the deshielding impact of oxygen (Van Loo et al., 1986).Natural colorants known as anthocyanins have gained popularity due to their broad array of colors.The intense redorange to blue-violet color of anthocyanins that develop under acidic conditions is a consequence of the chromophore of eight conjugated double bonds supporting a positive charge on the heterocyclic oxygen ring (Bueno et al., 2012).In addition to the positive charge in the ring structure, the quantity and arrangement of aromatic hydroxyl groups and conjugation allows protons to be easily attributed to highly reactive free radicals, thereby interrupting the formation of new radicals (Leopoldini et al., 2011) (Figure 4).

| Stilbenes
Stilbene is related to the class of phytoalexins that play a role in plant defense against stress, infection, and injury.The stilbene structure contains two benzene rings connected through ethanol or ethylene.1,2-Diphenylethylene can be further categorized into monomeric and oligomeric stilbenes (Shen et al., 2009).Monomeric structures composed of simple aglycones with two aromatic rings coupled through an ethylene bridge exist in the most common configuration, the trans isomer (E).Oligomeric stilbenes have diverse skeletons and complex configurations.The differences in oligomerization between homogeneous and heterogeneous monomeric stilbene couplings are shown in Figure 5.The most common secondary plant metabolite of the stilbene class is 3,5,4 0 -trihydroxystilbene.
Resveratrol is excised in both cis and trans isomeric forms.Edible berries, including stilbenes, exhibit increased diversity of bioactive compounds, and the quantity and quality of these bioactive compounds depend on the environmental conditions.E-resveratrol extracted with 2 μg/g content from bill berry and 4 μg/g content from blueberries using LC-MS.Passion fruit loaded with highest amount of quantity of stilbenes and 85,400 μg/g of piceatannol effectively extracted seeds.A high concentration of E-resveratrol (2680 lg/g) was extracted from Vitis vinifera L. (Vitaceae) (Błaszczyk et al., 2019).Determination of the double bond geometry is a key step in elucidating the structure of stilbenes and is easily determined via measurement of the coupling constant between two protons via proton NMR spectroscopy for vinylic protons.The nonplanarity of the trans stilbene has been demonstrated by liquid crystal NMR spectroscopy, which also revealed the coexistence of four stable rotamers (Celebre et al., 2012).

| Lignans
Lignans are built up with an adibenzylbutane skeleton, and in the plant kingdom, they participate in lignin production, which ultimately results in the construction of a plant cell wall (Liu et al., 2018).Although lignans have been found in each part of plants, their concentration is highest in wood, especially within wood knots (Willför et al., 2006).
F I G U R E 3 Chemical structures of isoflavonoids and coumestans.
Lignans and isoflavonoids are unique biochemical components, as phenolic groups at both ends of their molecular structure provide increased stability (Figure 6) (Adlercreutz, 1998).The stereochemistry of the flax lignan seeds was investigated using chiral HPLC, which revealed that matairesinol and secoisolariciresinol comprised primarily one enantiomorph (Smeds et al., 2012).
However, lignans perform useful roles in higher plants, and they are also detected in the biological fluids of humans and animals (Setchell et al., 1980).The two special mammalian lignans, which are identified in blood plasma, bile, and urinary excretions, enterodiol, and enterolactone, are metabolites of the plant lignans secoisolariciresinol and matairesinol, respectively, and are metabolized by gastrointestinal flora (Alseekh et al., 2020;Clifford, 2001;Savic et al., 2013).Enterodiol can be further metabolized to enterolactone (Figure 7) (Borriello et al., 1985;Setchell et al., 1984).

| Other classes of phytoestrogens
In addition to common phytoestrogens, several structures that exist in the plant kingdom and have estrogenic activity are utilized by humans as herbal remedies.Ginseng is an ancient remedy that contains triterpenoids and saponins.Ginsenoside Rg1 was found to be a phytoestrogen that exerts estrogenic effects without interacting directly with estrogen receptors in breast cancer cells (Vivek P. Chavda, Balar, Teli, et al., 2023;Lau et al., 2008).Ginsenoside-Rb1 was found to be an estrogen receptor agonist that inhibits capillary morphogenesis (Ong, 2015;Papapetropoulos, 2007).Moreover, many herbal medicines are estrogenic plants that are used in various healing processes and contain bioactive compounds such as terpenoids, phenolic compounds, quinines, and anthraquinone (Echeverria et al., 2021).

| Biosynthesis of phytoestrogens
Phytoestrogens are synthesized in higher plants to play a role in shielding plants from UV rays, pathogen assault, and stress-related reactions such as dehydration.Edible plant parts, including seeds, roots, stems, leaves, and fruits, contain hundreds of different polyphenolic structures (Manach et al., 2004).The biosynthesis of phytoestrogens is well explained by the role of specific enzymes involved in the shikimic acid and calpolymalonate pathways (Winkel-Shirley, 2001).
Biosynthesis follows the phenylpropanoid pathway, with F I G U R E 4 Chemical structures and extended subclasses of flavonoids.
F I G U R E 5 Chemical structures of stilbenes.phenylalanine serving as the starting material, which is converted to p-coumaroyl-CoA (Figure 8) (Ferrer et al., 2008).The condensation of one p-coumaroyl-CoA molecule and three malonyl-CoA molecules results in the formation of a chalcone scaffold.Chalcones serve as precursors for the development of different polyphenolic chemicals, including proanthocyanidins, isoflavonoids, and flavonoids (García-Calderón et al., 2020).Chalcone isomerase (CHI) catalyzes the cyclization of chalcones or deoxy chalcones to form the flavonoid core flavanone.The phytoestrogen composition from various sources varies depending on several factors, such as postharvest factors and genetic and agronomic factors (Tomás-Barberán & Espín, 2001).Vascular plants contain a broad population of lignans.Lignans are synthesized after the oxidative dimerization of two phenylpropanoid units (Di Gioia & Petropoulos, 2019).Nonetheless, lignans exhibit a wide adaptive distribution alongside structural, enantiomeric, and biosynthetic diversity (Umezawa, 2003).
F I G U R E 6 Chemical structures of the most common plant lignans.
F I G U R E 7 Possible transformation pathway of dietary lignans to mammalian lignan production.
The four key enzymes involved in the biosynthesis of phytoestrogens are L-phenylalanine ammonia-lyase, chalcone synthase (CHS) chalcone reductase (CHR), and CHI.In the phenylpropanoid pathway, the first rate-limiting step is catalyzed by PAL.L-Phenylalanine ammonia-lyase exists as an α-helix with a homotetramer shape and as a cofactor for the electrophilic prosthetic group 4-methylidene-imidazole-5-one.One study reported that tobacco petals and lettuce leaves with upregulated PAL produced more genistein (Liu et al., 2007).The PAL reaction is initiated by MIO interacting with the amino group or the aromatic ring of the phenylalanine substrate via carbanion or carbocation intermediates to eliminate ammonia and generate trans-cinnamate (Pezeshki et al., 2022;Ritter & Schulz, 2004).Cinnamate 4-hydroxylase is the second enzyme that converts cinnamate to p-coumarate.4-Coumarate CoA-ligase catalyzes the conversion of p-coumarate to p-coumaroyl-CoA.Stilbene synthase (STS) converts p-coumaroyl-CoA to resveratrol, and the substrate subsequently undergoes aldol-type cyclization and decarboxylation processes.The wilting process and UV irradiation influence the induction of STS and the synthesis of resveratrol (Versari et al., 2001).chalcone derivatives.The first known enzyme implicated in the production of flavonoids is CHI, which is also the second rate-limiting enzyme in the pathway.The intramolecular cyclization process that generates tricyclic (2S)-flavanone from bicyclic chalcone is catalyzed (Yin et al., 2019).CHI stereospecifically catalyzes cyclization to produce flavonoids to core flavanones.CHI spontaneously converts chalcone to 6 0 -deoxychalcone to give enantiomeric mixtures of (2S)naringenin (Figure 9) (Austin & Noel, 2003;Bomati et al., 2005;Jez et al., 2000;Morita et al., 2001).
The next progressive step of biosynthesis is the formation of isoflavones, starting with dramatic migration of the aryl ring from C2 to C3 and resulting in double bond formation catalyzed by isoflavone synthase (also named 2-hydroxyisoflavanone synthase [2-HIS]), which transforms flavanone to 2-hydroxyisoflavanone.Then, 2-hydroxyisoflavanone dehydratase (2-HID) catalyzes the dehydration of 2-hydroxyisoflavanones to yield the first isoflavone products.The formation of daidzein or genistein is shown in Figure 10 ( Akashi et al., 2005;Wang et al., 2022).2-HIS is a cytochrome P450 enzyme that is membrane associated and classified as part of the CYP93C subfamily, while the 2-HID enzyme belongs to a broad family of carboxylesterases.
Soflavone-O-methyltransferase yields methyl ether derivatives, for example, formononetin, by transferring one methyl group to isoflavones from S-adenosyl-L-methionine. Hydroxylation of isoflavonoids such as genistein and formononetin is catalyzed by isoflavone 2 0hydroxylase, which produces 2 0 -hydroxyl isoflavones.Isoflavone reductase (IFR) and vestitone reductase (VR) are NADPH-dependent reductase enzymes that play roles in the biosynthesis of medicarpin.

| Overview of the therapeutic potential of phytoestrogens
Several different compounds are present in the phytoestrogen group and have structures similar to those of 17-β-estradiol (OE) (Rietjens et al., 2017).OE plays a major role in females by contributing to maturity, the menstrual cycle, and a better reproductive system.
Proper fertilization and implantation are facilitated by thickening of the uterus wall, which is facilitated by the OE.However, a decrease in the concentration of phytoestrogens does not have a major impact on the body but can trigger deficiency syndrome (Vašková et al., 2023).Phytoestrogen is not directly involved in any essential biological functions and hence is not treated as a nutrient to the human body.These compounds usually bind to the estrogen receptor present in the body due to their structural similarity to that of the OE and thus exhibit antiestrogenic effects.Few researchers have hypothesized that these types of phytoestrogens are used by plants as defensive weapons against animals to inhibit female fertility.This pest controls herbivorous animals by inhibiting overpopulation and overgrazing (Wyse et al., 2022).
Phytoestrogens are used to address problems associated with menopause, such as hot flashes and osteoporosis (Chen & Chen, 2021).They also decreased cardiovascular risk, metabolic syndrome, and obesityrelated problems (Chen & Chen, 2021).The high intake of soy isoflavone food in some countries, such as Japan, has resulted in phenomenal effects, the so-called Japanese phenomenon, which helps people become exposed to limited cases of chronic diseases compared to those in Western countries (Nagata, 2010).

| Phytoestrogen mode of action through interaction with estrogen receptors
Researchers have explored the types of receptors involved in the OE, including estrogen receptor α (OEα) and estrogen receptor β (OEβ), in animals such as rats, mice, primates, and humans.These types of receptors associated with the OE are involved in the regulation of different functions, such as gene regulation and cancer biology (Chen et al., 2022).The tissue maintenance and growth of the breast along with the uterus are involved in the activation of OEα.Moreover, they have an impact on uncontrolled growth, especially in the case of OEαdependent breast cancer in humans (Chic et al., 2021).These types of issues are usually treated with antiestrogenic therapy, such as tamoxifen.The stimulation of OEα cell proliferation is counteracted by OEβ.
As OEα and OEβ have different effects on each other, the level of phytoestrogens in the body will lead to different responses to cell proliferation and gene regulation based on the presence of high or low levels of these two compounds in the body (Wang et al., 2021).The difference in the actions triggered by OEs is supported by their respective coactivators and corepressors after activation, and they might interact with the nuclear receptor.Therefore, the action of phytoestrogens as agonists or antagonists is dependent upon the actual F I G U R E 1 0 Biosynthesis of isoflavones from flavanones by the reaction catalyzed by 2-HIS and 2-HID.level of endogenous estrogen present in the body (Lecomte et al., 2017).

| Phytoestrogen-triggered epigenetic effects
Epigenetic mechanisms are responsible for the health effects induced by phytoestrogens.The epigenome is generally related to the chemical changes in DNA and histone proteins present in organisms.With the help of the transgenerational stranded type of epigenetic inheritance, changes in DNA and related histone proteins are passed down to subsequent organisms (Guerrero-Bosagna & Skinner, 2014).Major epigenetic changes occur, which further result in alterations in gene expression.The expression of these genes is related to cell proliferation and differentiation.Therefore, phytoestrogens impact cell proliferation through the epigenetic route.In the case of phytoestrogens, the prime components that are assessed for this purpose are genistein and daidzein (Choi et al., 2014;Singh & Paramanik, 2022).From a chemical point of view, both are soy isoflavones.In many diseases associated with humans, such as obesity, epigenetic modifications are related to genistein consumption.These modifications induce DNA methylation along with microRNA regulation.Histone modifications are also related to each other.Many studies have demonstrated the impact of genistein on DNA methylation (Pudenz et al., 2014).

| Other possible actions associated with phytoestrogens
Genistein affects cells, particularly those exposed to genistein, through the activation of adenosine monophosphate-triggered protein kinases.The proper mechanism for this type of activation has still not been explored, but the release of reactive oxygen species (ROS) into the cell is thought to be stimulated through genistein.The second type of action, which is correlated with phytoestrogens, is kinase inhibition (Mittal et al., 2014).These protein kinases are associated with diseases and are possibly related to phytoestrogen effects.Phytoestrogens also affect nuclear receptors, such as peroxisome proliferatoractivated receptors (PPARs) (Hassan et al., 2021).These genes are related to those of the nuclear receptor superfamily and act as factors in ligand-activated transcription; these genes can be divided into three subtypes: PPARα, PPARγ, and PPARβ.The regulation of triglyceride levels and energy homeostasis are related to PPAR-α (Lamichane et al., 2018).The activated receptor PPARδ is expressed in oxidative tissues and helps regulate the genes associated with substrate delivery.PPARγ is present predominantly in white adipose tissues and is required for lipogenesis and lipid synthesis in the body (Sun et al., 2021).Therefore, these types of activated receptors play major roles in fat regulation and immune cell differentiation.Phytoestrogens also have an impact on the erythroid 2-related type 2 Keap 1 signaling pathway.This protein acts as a nuclear factor (NF) and is responsible for the induction of antioxidant-embedded responses completed by electrophiles (Ma, 2013).The adverse effects induced by these agents are associated with gene expression induction, which enhances the cellular defense mechanism against ROS, as do electrophiles.In CVD, this pathway is activated to protect against tumor induction and oxidative stress.A specific gene polymorphism also plays a very important role in the action triggered by phytoestrogens (Christofides et al., 2021).Wound healing is influenced by the physiological cycle and dynamically changes with aging in humans.A high concentration of estrogen enters the preovulation phase, contributing to tissue repair.The OEβ also plays an important role in tissue repair, as demonstrated by Ahn et al., through biomimetic and estrogenic fibers.Soy phytoestrogens were explored due to their preferential binding to ERβ and ability to bind to engineered nanofibers by using hyaluronic acid.Skin repair is facilitated through ER-β activation through estrogenic fibrous scaffolds (Ahn et al., 2020).

| Role of phytoestrogens in reproduction
Phytoestrogen stimulates the animal ovarian type progesterone in combination with the production of cyclic adenosine monophosphate (Wocławek-Potocka et al., 2013).The maturation of the oocyte during the development of the zygote in the preimplantation stage is also impacted by exogenous estrogen-like molecules.The phytoestrogens obtained from plant sources, such as green tea and Indian turmeric, inhibit cell proliferation, thus promoting apoptosis (Salehnia & Zavareh, 2013).The release of steroid hormones through porcine ovarian cells also changes.Soybean products in the diet have major effects on health, as they contain a high percentage of isoflavones.
The development of animal sexual processes can be altered from that of soybean product consumption.In addition, there are several major changes associated with this phenomenon, including alterations in pubertal timing, estrous cycling, and ovarian function (Dinsdale & Ward, 2010).There is evidence that isoflavone intake may trigger changes in pituitary function as well as alterations in hypothalamic activity.The phytoestrogens obtained from isoflavones in combination with lignans have interesting effects on the female body, such as the inhibition of menopausal symptoms involving hot flashes (Messina, 2016).They also impact other symptoms, such as vasomotor symptoms and vaginal atrophy.Phytoestrogens have no direct effects on endometrial or breast health.These compounds often act as alternatives to hormonal replacement therapy in postmenopausal women, and preferred intake is provided through food supplements (Fait, 2019).Equol, a metabolite derived from the soy component daidzein, stands out among other isoflavones for its potent estrogenic and antioxidant properties.This has triggered much enthusiasm for its potential health benefits, ranging from menopausal symptom relief to cancer prevention.Only a select group of individuals, approximately 30-50% of whom are part of the population, can reap these benefits directly from soy consumption.While everyone can convert daidzein to some extent, only specific gut bacteria possess the enzymatic machinery to fully transform it into the high-power equol.In the future, routine gut microbiome analysis could predict a person's equol-producing capacity, guiding personalized dietary recommendations for maximizing the health benefits of soy and isoflavones.This targeted approach holds immense promise for harnessing the full potential of these natural treasures, ensuring everyone gets the most out of their plant-based diet (Mayo et al., 2019).Women at risk of clotting through hormonal therapy are diverted to compounds such as lignan, which seems to be a better option for hormonal replacement therapy with less risk of clotting.Menopause also leads to changes in psychological and somatic vegetative background symptoms, which are impacted by the intake of phytoestrogens (Ţit ȩt al., 2017).Lee et al. studied  and a rat model.The uterotrophic effect suggested that the selected phytoestrogens regulated the expression of uterine genes in other ways than estrogen did.Second, the study revealed that the interaction of phytoestrogens with ER-α was crucial for effective screening of these compounds for therapeutic action (Sim et al., 2022).

| Phytoestrogen effects on the immune system
Transcription factors such as NF kappa β are required for the smooth conduction of vents into the body (Mostafizar et al., 2021).These NFs are involved in several immunologically relevant diseases, such as allograft rejection, rheumatoid arthritis, and bronchial asthma.These factors can be induced by heterodimers that contain NF-kβ1 as well as RelA.These proteins are related to the NF-kβ/Rel protein family, which influences regulatory T cells and are important for the maintenance of immune homeostasis and the inhibition of autoimmune diseases (Ghosh & Wang, 2021).Genistein has been demonstrated to have a significant impact on the suppressive effect of antigen-specific immune responses in vivo and on the proliferation of lymphocytes in an in vitro study model.Along with cytokine generation, the cytotoxic response of T cells increases in response to genistein.Therefore, the action of genistein is cell dependent, but this type of confirmation requires proper validation and a more in-depth assessment of the same phenomenon (Chavda, Balar, Vaghela, et al., 2023;Chavda, Chaudhari, Teli, et al., 2023;Chavda, Nalla, Balar, et al., 2023;Vivek P. Chavda, Teli, Balar, et al., 2023;Lee & Burckart, 1998;Ronin et al., 2019).Sadeghi et al. studied the impact of soy milk consumption, that is major source of phytoestrogens, on the gut microbiota, inflammatory markers, and disease severity in ulcerative colitis patients through randomized clinical trials (Sadeghi et al., 2020).

| Phytoestrogen contribution to osteoporosis
A lower concentration of estrogen in the body leads to a bone turnover effect, which can be further intensified by bone reabsorption.
This increase in bone resorption can be confirmed by the functional activity of osteoclasts.Gonadal dysfunctions have effects on epiphyseal growth plates, which have delayed closure (Bassett & Williams, 2016).Therefore, fewer gonadal steroids in the body result in defective periosteal growth of the bone, which increases the risk of osteoporosis later in life.Estrogen also plays a major role in skeletal maturation in males.Therefore, estrogen deficiency affects the skeletal maturation and a decrease in bone mass (Thapa et al., 2022).This leads to increased endocortical resorption and increased intracortical porosity of the bone.This results in disturbed bone architecture, reduced bone strength and reduced bone mass.Estrogen also controls the number of osteoclasts present at the cellular level.It prohibits the differentiation of osteoclasts and therefore helps to decrease the number of active remodeling units in the body (Manolagas et al., 2013).Several phytoestrogens, such as genistein and daidzein, in combination with coumetarol, have shown bone-sparing effects in rats.The efficacy of these treatments is dependent upon many factors, including the dose of the phytoestrogens, duration of action, and type of animal model utilized.The compound equol, which is obtained from daidzein, is required for the bone-sparing effect.In some adults, equol is produced from intestinal bacteria, and these adults receive greater benefit from soy isoflavone than others (Mayo et al., 2019).In another study, approximately 39 phytoestrogen compounds were predicted to have antiosteoporosis activity through an in silico approach via the use of the raloxifene and SwissADME web tools.For example, Ma'arif et al. studied this topic by using molecular docking via PyRx 0.8 software and the AutoDock Vina method.The software used was used for the prediction of Erβ agonist activity in selected compounds, while pkCSM was used for the determination of hepatotoxicity, skin sensitization and Ames toxicity.Catechin in combination with epicatechin was the most potent of the selected 39 phytoestrogens, along with the nontoxic antiosteoporosis compounds (Pandey & Rizvi, 2009).A study in rats suggested that standardized hop extracts of a compound called 8-prenylnaringenin could help prevent bone loss without affecting the uterus.Compared with those in the control group, rats given 60 mg of the extract per kilogram of body weight for an unspecified period exhibited increased bone density.The blood levels of 8-prenylnaringenin, another similar compound called 6-prenylnaringenin, and a precursor molecule called isoxanthohumol were also measured.However, it is important to note that this study was conducted in rats, and similar effects have not yet been observed in humans (Keiler et al., 2017).

| Natural phytoestrogens as neuroprotective agents in Parkinson's disease
There is a decrease in dopamine receptors in Parkinson's disease (PD) patients, accompanied by a combination of symptoms, including rigidity, resting tremor, and several postural abnormalities.A decrease in dopamine in the body leads to several effects, including oxidative stress, protein misfolding, excitotoxicity, neuroinflammation, and mitochondrial dysfunction (Pinjala et al., 2023;Samim Khan et al., 2023;Sarkar et al., 2016).As such, there are no effective therapies available to cure PD completely, but some symptomatic treatments are available for treating this disease; the details are presented in The induction of dyskinesias in PD patients treated with L-DOPA limits their quality of life, and there is a demand for more suitable treatment options (Naren et al., 2023;Rajan et al., 2023).The difference in the incidence of PD between males and females may be due to differences in gonadal hormone exposure between the two sexes (Khatri et al., 2023).Additionally, the occurrence of PD at an early age in the male subgroup was also based on the same reasoning.The delayed disturbance in the motor symptoms of PD in women may be due to hormonal differences from that in men (Kwon et al., 2022).The neuroprotective effects of phytoestrogens on PD involve three crucial  AutoDock Vina (PyRx 0.8) was used for molecular docking of compounds for ERα (1A52) and ERβ (5TOA).The results showed that the equol compound was similar to 17-β-estradiol, which is a native ligand.The same compound was shown to bind to the ERα (1A52) and ERβ (5TOA) receptors, which further helped to inhibit neurodegeneration through an ER-dependent pathway (Muslikh et al., 2022).

| Role of phytoestrogens in SARS-CoV-2
COVID-19 involves different types of symptoms associated with acute respiratory syndrome, high fever, weakness, and, in several cases, death due to respiratory failure (Figure 12).Natural products are implemented to address these symptoms, particularly to boost immunity to combat the virus and eradicate it from the body (Chavda, Chaudhari, Teli, et al., 2023;Vivek P. Chavda, Khadela, Shah, et al., 2023, Teli et al., 2023).Phytoestrogens are thought to help stabilize the renin-angiotensin-aldosterone system, which plays a significant role in coronavirus invasion into cells.Therefore, further multiplication and spreading of the virus into the body decreases due to the barriers created by phytoestrogen through a stabilized version of this system (Farooq et al., 2023).

| Role of phytoestrogens in cancer
Cancer invasion into the body induces different types of effects, including the cancerous transformation of normal cells with uncontrolled growth and tumorigenesis (Vivek P. Chavda, Balar, & Patel, 2023d;Chavda, Chaudhari, Teli, et al., 2023;Chavda, Nalla, Balar, et al., 2023).These effects occur in the body due to several disturbed or altered mechanisms involved in DNA mutagenesis and cell proliferation (Desmawati & Sulastri, 2019).Phytoestrogens such as genistein have been tested for their anticancer potential due to their ability to induce modulation of the cell cycle and apoptosis.It also has the potential to prohibit the activation of NF-kB and the Akt signaling pathway.These signaling pathways are vital for the maintenance of homeostasis and cell survival, as is apoptosis.Phytoestrogen was used to inhibit angiogenesis and metastasis processes by utilizing its antioxidant potential, thus controlling the major damage that occurs during cancer (Patra et al., 2023).However, some of the related studies contradict this finding and involve breast cancer patients treated with phytoestrogens (Andrew & Izzo, 2017;Patisaul & Jefferson, 2010;Setchell & Clerici, 2010;Sirotkin & Harrath, 2014).
F I G U R E 1 2 Role of phytoestrogens in COVID-19 management.Phytoestrogen mainly helps in decreasing the spread of the virus by stabilizing the renin-angiotensinaldosterone system.

| Role of phytoestrogens in hormonally dependent disease
The enzymes that are inhibited by phytoestrogens include type 1 and type 2 17β hydroxysteroid oxidoreductases, along with 5α-reductases and aromatase.Phytoestrogen can also bind to globulin to stimulate sex hormone production in the body.On theoretical basis, phytoestrogens are thought to be useful for modulating the production and bioavailability of endogenous steroidal hormones, such as estrogens and androgens, which can induce hormone-or antihormone-like activity.The various applications of phytoestrogens in several disease conditions are tabulated in Table 1 (Strauss et al., 1998).

| PRESENT PRECLINICAL AND CLINICAL DEVELOPMENT
Along with all the theoretical claims and imagination, it is essential to check the effectiveness and safety of any novel or preexisting molecule to make it compatible with human use.Before turning our heads toward clinical or human trials, every drug undergoes preclinical screening.to evaluate embryo-uterine attachment (necessary for implantation) (Brown & Setchell, 2001;Wang et al., 2005).It was observed that The effects and association of phytoestrogens against various diseases.

Renal disease protection
Retard the progression and development of renal disease by reducing proteinuria along with renal pathological lesions associated with the progressive renal disease.

Anxiety and affective disorders
It helps in anxiety and affective disorders especially in women due to their estrogenic activity modulated through OE receptors.However, there is slight variation in the given results depending on the concentration of phytoestrogens.Low phytoestrogen inhibits the aromatase and prohibits testosterone biotransformation while the high concentration of the same induces an estrogen-like effect modulated through inhibition of the tyrosine kinase.(Chakraborty et al., 2023) Rheumatoid arthritis Phytoestrogens can suppress NF-κB activity which is crucial for the release of inflammatory cytokines release into rheumatoid arthritis.The signaling pathways for NF-κB induce the phosphorylation for the complex of IκBα/NF-κB which further leads to polyubiquitination for the IkB proteins.These proteins causes the translocation of the NF-κB and contribute to the release of cytokines, thus generating inflammation.(Lei et al., 2002) Liver disease Estrogen-like activity of the phytoestrogen helps to modulate the risk of hepatocellular carcinoma in patients suffering from liver cirrhosis.(Agretti et al., 2018) Thyroid iodide uptake and thyroid gland function The estradiol does not have an impact on the iodide uptake.However, high doses of isoflavone along with triterpene-rich extracts have demonstrated significantly diminished iodide uptake.
Along with that, it also not influencing sodium iodide symporter mRNA expression into that of the FRtl-5 cells.(Sosvorová et al., 2012) The phytoestrogens may enter into the thyroid follicles.They also have an influence on thyroid peroxidase but the phytoestrogen as such does not have a direct impact on the development of the disorders related to that of the thyroid gland.(Farooq et al., 2023) COVID19 Phytoestrogen helps COVID patients through the modulation of the reninangiotensin-aldosterone system (Vivek P. Chavda, Balar, & Patel, 2023e;Kalervo Väänänen & Härkönen, 1996) Osteoporosis It prevents the differentiation of the osteoclasts and therefore they help to decrease the remodeling units active units into the body.(Setchell & Clerici, 2010) Cancer Phytoestrogen like genistein has been tested for its anticancer potential due to its ability to induce modulation into the genes controlling the cell cycle along with apoptosis to that in the control group.It also helps in the reduction of thiobarbituric acid-reactive substances (TBA levels), which increase glutathione levels via antioxidant action.Overall, these various effects lead to effective memory conservation in mice, in addition to additional effects, such as antioxidant effects.Cholinergic therapy and a reduction in cholesterol levels have been used (Bansal & Parle, 2010).
With supporting preclinical data, it is necessary to ensure a similar promising effect in the initial screening procedure in humans.Together, these factors may help lower "bad" LDL cholesterol and increase "good" HDL cholesterol, contributing to a healthier heart and potentially reducing the risk of cardiovascular diseases (Masood et al., 2010).Phytoestrogens, particularly isoflavones such as genistein and daidzein, can mimic the effects of estrogen and can help maintain bone health, especially in postmenopausal women, potentially reducing the risk of osteoporosis (Qureshi et al., 2011).The anti-inflammatory and antioxidant properties of certain phytoestrogens, particularly lignans and isoflavones, have attracted the attention of researchers in the field of cancer prevention (Gorzkiewicz et al., 2021).Along with these benefits, it has several disadvantages, especially when used at excessive concentrations.High intakes, especially in those with preexisting hormonal imbalances, may contribute to estrogen dominance.This can cause breast tenderness, irregular periods, and mood swings and, in rare cases, potentially increase the risk of certain estrogen-sensitive cancers.Some phytoestrogens, such as isoflavones, may hinder thyroid hormone production, potentially leading to hypothyroidism or worsening of existing thyroid problems.Excessive intake may affect fertility in both sexes (Patisaul & Jefferson, 2010).In men, it could impact sperm health and reduce reproductive potential.In women, exercise may disrupt menstrual regularity and ovulation, hindering fertility.While uncommon, some individuals may develop allergic reactions to certain phytoestrogen sources, with symptoms such as itching, hives, swelling, or respiratory issues.While phytoestrogens offer potential health benefits, moderate intake is crucial, especially for individuals with hormonal imbalances or underlying health conditions (Desmawati & Sulastri, 2019).Consulting a healthcare professional before significantly increasing intake is recommended.Numerous animal studies have evaluated the effectiveness of phytoestrogens, but clinical trials are limited.Moving beyond animal models, robust human research is key to revealing the true impact of phytoestrogens on human health.
Understanding how these plant-based molecules interact with human physiology and influence health outcomes is necessary.This knowledge is crucial for developing informed recommendations about phytoestrogen intake, especially for vulnerable populations such as pregnant women, individuals with health conditions, and those at different life stages (e.g., menopause).Rigorous clinical trials are essential for determining safe and effective dosages for various groups, while long-term studies will shed light on the long-term consequences of phytoestrogen consumption, particularly concerning hormone-related conditions and cancer risks (Wyse et al., 2022).Therefore, comprehensive research and clinical trials in humans are still needed to fully explore the potential benefits of these molecules.It can be conducted by various methods, including longitudinal studies, randomized controlled trials, multiomics approaches, population-based studies, interdisciplinary collaboration, adverse event monitoring, and so forth.Interdisciplinary collaboration is preferred because experts from diverse fields, including nutritionists, endocrinologists, oncologists, geneticists, and epidemiologists, which helps in unlocking holistic perspectives.
The ubiquitous enzyme CHS catalyzes the forward steps toward flavonoid biosynthesis through the addition of three malonyl-CoA molecules to one p-coumaroyl-CoA molecule that forms a chalcone scaffold.This step was completed by intramolecular cyclization, aromatization, and decarboxylation.The CHR enzyme, which is detected only in leguminous plants, acts on CHS and synthesizes deoxy chalcone.CHRs play unique roles in the production of a variety of deoxy F I G U R E 8 Biosynthesis of several phytoestrogens through the phenylpropanoid pathway.F I G U R E 9 Stereospecific catalyzed cyclization through chalcone isomerase.
the estrogenic activity of the estrogen receptor, mycoestrogen (3β, 5α, 22E)-Ergost-22-en-3-ol, with the help of α-dependent signaling pathways.The influence of phytoestrogens on the proliferation of the MCF-7 breast cancer cell line was studied using a cell proliferation assay.The mechanism of action is related to the expression of the extracellular signal-regulated kinase OEα and phosphatidylinositol 3-kinase.It was concluded that the selected plants have great potential for their estrogenic potential in menopause (Lee et al., 2021).Several researchers have performed comparative studies of estrogenic activities by using Organization for Economic Co-operation and Development through in vitro and in vivo testing methods.Sim et al. studied 15 phytoestrogens via an ER-α dimerization assay and a transactivation assay in VM7Luc4E2 cells
Figure 11.Under prolonged and excessive ROS and RNS stress conditions, different types of cytotoxic mediators, including tumor necrosis factor, interleukin-1β, and interferon-γ, can damage cells via the overexpression of pro-inflammatory cytokines.This type of overexpression also includes the involvement of inducible nitric oxide synthase and cyclooxygenase 2 overexpression (Ceccarelli et al., 2022; Zhao et al., 2021).Muslikh et al. studied the potential of phytoestrogens for treating neurodegenerative diseases by using in silico molecular docking and ADMET analysis.Many phytoestrogens, such as genistein, daidzein, and glycitein, have been studied, while pharmacokinetic and pharmacodynamic studies have been conducted using SwissADME.Avogadro 1.0.1 was used for geometric optimization of the compounds, while

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for obesity control by giving hyperlipidemia, and reduction into the body weight.They also help to decrease plasma total cholesterol along with lower low-density lipoprotein (LDL) cholesterol.(Bhathena & Velasquez, 2002) DiabetesIt improves glucose control and insulin resistance issues.It induces the reduction of the serum insulin and thus helps the hyperglycemic condition to get recovered.(Rodríguez-Landa et al., 2018)

NCT01741974 5 |
• Effect of karat on the thickness of common carotid arteries and change in cholesterol deposition in cultured cells.CONCLUSION  AND FUTURE DIRECTIONSEstrogen, now primarily preferred in the form of phytoestrogens, is a natural nonsteroidal polyphenolic compound that mimics the activity of estrogen.It comprises various chemical moieties, such as flavonoids, isoflavones, and lignans.The biosynthesis of phytoestrogen plays a crucial role in its function.This process begins with simple amino acids such as phenylalanine and tyrosine, which transform into key building blocks called cinnamic acid derivatives.These derivatives then undergo a series of intricate modifications guided by specialized enzymes such as CHS and isoflavone synthase, ultimately revealing the diverse classes of phytoestrogens(Cao et al., 2020).Moreover, these agents maintain their effectiveness in treating numerous homeostasis imbalances, including cardiovascular disease, metabolic syndrome, cancer, neurodegenerative disease, and skin disease.When estrogen levels decrease, these plants increase, offering a gentle boost to maintain hormonal harmony.In situations with high estrogen concentrations, phytoestrogens work by blocking stronger estrogens from binding to receptors and keeping things in check(Van Duursen, 2017).Phytoestrogens also work by improving the flow of blood by influencing cholesterol levels.
Brown et al. testedthe effect of different phytoestrogens in mice.Purina 5008, Purina 5010, NIH-07, AIN-76A, AIN-93G, and AIN-93 M were used to determine the influence of each individual.Adult mice administered Purina 5008, Purina 5010 or T A B L E 2 Clinical trials of phytoestrogens as therapeutic agents.
tive sense.As a diversified moiety, it is also claimed to reverse age and memory deficits in Swiss albino mice.Soybean supplement was administered to the mice for 60 days at concentrations of 2, 5, and 10% w/w.The activity of acetylcholine was deducted, and the total cholesterol level was reduced compared

Table 2
describes the ongoing trials on phytoestrogens in the treatment and management of various diseases and disorders.