Chrysin

Chrysin (5,7-Dihydroxyflavone): A Comprehensive Reference

1. Identity: Chemical Name, Classification, and Natural Sources

1.1 Chemical Identity

Chrysin, also called 5,7-dihydroxyflavone, is a flavone found in honey, propolis, the passion flowers Passiflora caerulea and Passiflora incarnata, and in Oroxylum indicum. It is a naturally occurring flavonoid in which the two hydroxy groups are located at positions 5 and 7, with a molecular weight of 254.24 g/mol and the chemical formula C₁₅H₁₀O₄. Chrysin belongs to the class of dihydroxyflavones, characterized by hydroxyl groups attached solely to the aromatic A-ring — specifically at the 5 and 7 positions — distinguishing it from other flavones.

Chrysin, which has the ubiquitous 15-carbon flavone backbone, is one of the most important bioactive constituents of different fruits, vegetables, and even mushrooms. It has a common chemical structure, consisting of two fused rings, A and C, and a phenyl ring, B, attached to the second position of the C ring. Notably, unlike many flavonoids, chrysin contains only hydroxyl groups on ring A (5,7-dihydroxyl) and no substituents on ring B.

Among the wider flavonoid family, which also includes flavonols and flavanones, chrysin is particularly notable for its unique chemical structure and specific pharmacological effects. These effects encompass significant antioxidant, neuroprotective, and anti-inflammatory properties, all of which have attracted increasing scientific interest.

1.2 Natural Sources

Chrysin is found in honey, propolis, the passion flowers Passiflora caerulea and Passiflora incarnata, in Oroxylum indicum, carrots, chamomile, many fruits, and in mushrooms, such as the mushroom Pleurotus ostreatus. Chrysin (5,7-dihydroxyflavone) is a flavonoid isolated from plants such as Passiflora coerulea, Passiflora incarnata, and Matricaria chamomilla. Chrysin has been shown to be the main ingredient of some medicinal plants, such as Radix scutellariae, Lactarius deliciosus, and Passiflora incarnata.

The amount of chrysin in honey from various plant sources is about 0.2 mg per 100 g, and chrysin is typically found at higher amounts in propolis than in honey. A 2010 study found the amount of chrysin was 0.10 mg/kg in honeydew honey, and 5.3 mg/kg in forest honeys.

Chrysin is mostly insoluble in water but dissolves in organic solvents. In plants, it tends to concentrate in pollen, bark, and aerial parts.

1.3 Commercial Preparations and Dosage Forms

Chrysin is an ingredient in dietary supplements. It is commercially available in several forms. Chrysin is often incorporated into nanoscale delivery systems (niosomes, lipid nanoparticles, nanovesicles), which enhance its solubility and efficacy in the treatment of cancers, neurodegenerative diseases, and infections. The synthesis of chrysin esters and amides with various functional groups increases metabolic stability and bioavailability, as confirmed by preclinical studies in animal models of metabolic and cancer-related diseases.

Nanoformulations of polyphenols, including chrysin, are made using various carrier methods, such as liposomes and nanocapsules. A randomized crossover trial provided the first clinical evidence that a micellar chrysin–quercetin–rutin formulation (LMC) can overcome the poor bioavailability of native chrysin, achieving a ~2–3-fold increase in systemic exposure and enhanced intestinal permeability.

2. Traditional and Historical Use

While chrysin itself was not isolated or named until modern phytochemical analysis, its natural sources have a long history in traditional medicine, particularly Passiflora species (passionflower) and bee-derived products like propolis and honey. Chrysin, a natural flavonoid, was commonly found in propolis and honey and traditionally used in herbal medicine.

Honey and propolis, two of the richest natural sources of chrysin, have millennia-long histories of use in multiple cultures. One of the richest natural sources of chrysin is propolis, a resinous mixture collected by bees from tree buds and used in bee products. Propolis has been used for centuries in traditional medicine due to its rich flavonoid content, including chrysin.

Passionflower species, which represent the primary botanical source of chrysin, were central to indigenous medicinal traditions. Passionflower has been used for centuries in traditional herbal medicine, especially by Native American and South American cultures, where it was valued for its calming effects and used to treat anxiety, insomnia, and nervous disorders.

In European herbal traditions, passionflower entered widespread use several centuries ago. In traditional European herb lore, passionflower tea was used as a calming night tonic, and chamomile was steeped to ease digestive troubles and support digestion — practices still common today.

It is important to note that historical users did not employ chrysin as an isolated compound. Traditional preparations involved whole-plant extracts, decoctions, teas, and bee-derived products whose medicinal activity was attributed to complex mixtures of constituents, chrysin being one of many phytochemicals present. Chrysin as a discrete chemical entity was first isolated and characterized through modern phytochemical methods in the twentieth century.

3. Key Constituents and Mechanisms of Action

3.1 Structural Basis of Activity

Chrysin's biological activity is primarily attributed to the presence of hydroxyl groups, which facilitate the neutralization of free radicals and the modulation of intracellular signaling pathways. Cellular uptake of chrysin and other flavonoids occurs mainly through passive diffusion; however, certain forms may be transported via specific membrane-associated carrier proteins.

3.2 Antioxidant Mechanisms

Chrysin's antioxidant capacity derives directly from its polyphenolic structure. Chrysin has been demonstrated to be a very potent flavonoid acting through a large number of pharmacological activities, including antiasthmatic activity through the suppression of inducible nitric oxide synthase (iNOS) and nuclear factor-κB (NF-κB), inhibition of histone deacetylase and DNA topoisomerases, cardioprotective activity via improving post-ischemic functional recovery, anti-inflammatory activity via blocking histamine release and pro-inflammatory cytokine expression, prevention of osteoporosis by activation of estrogen receptor/mitogen-activated protein kinase, and anticancer activity by endorsing cell death induced by tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL).

3.3 Anti-inflammatory Mechanisms

Chrysin demonstrates anti-inflammatory action through several mechanisms: it suppresses cyclooxygenase-2 (COX-2), an enzyme involved in prostaglandin synthesis that promotes inflammation; it inhibits phosphorylation and degradation of IκB-α, as well as the translocation of NF-κB, and reduces levels of TNF-α and IL-1β by inhibiting NF-κB expression.

Chrysin acts on various molecular targets and modulates different signaling pathways of inflammation (NF-κB, PXR, TBK1) and cellular metabolism (AMPK/AKT/ERK/PPAR).

3.4 Anticancer Mechanisms

Chrysin's ability to combat cancer arises from its multifaceted mechanisms of action, including the initiation of apoptosis and the inhibition of proliferation, angiogenesis, metastasis, and cell cycle progression. In many studies, chrysin has been shown to suppress pro-inflammatory cytokine expression and histamine release, downregulate nuclear factor kappa B (NF-κB), cyclooxygenase 2 (COX-2), and inducible nitric oxide synthase (iNOS), upregulate apoptotic pathways, inhibit angiogenesis and metastasis formation, suppress DNA topoisomerases and histone deacetylase, and downregulate tumor necrosis factor α (TNF-α) and interleukin 1β (IL-1β).

3.5 Neuroprotective Mechanisms

Chrysin has been reported to exert neuroprotective effects through different mechanisms, including anti-oxidant, anti-inflammatory and anti-apoptotic functions, MAO inhibition and GABA mimetic properties. In brain structures such as the hippocampus, prefrontal cortex, raphe nucleus, and striatum, involved in the physiopathology of anxiety and depression disorders, several neuropharmacological activities, including the activation of neurotransmitter systems (GABAergic, serotonergic, dopaminergic, and noradrenergic), neurotrophic factors such as brain-derived neurotrophic factor and the nerve growth factor, and some signaling pathways are affected.

3.6 Aromatase Inhibition

Chrysin, 5,7-dihydroxyflavone, is a potent inhibitor of the enzyme aromatase, which converts androgens to oestrogens. When 40 nM androstenedione was added as the substrate, 0.5 μM chrysin could inhibit 50 percent of the aromatase concentration (IC₅₀), and Ki values of chrysin were 0.26 μM. However, as detailed in Section 5 below, this in vitro potency does not translate to meaningful clinical effects following oral administration.

4. Bioavailability and Pharmacokinetics

The effects of chrysin are reliant on its bioavailability and solubility. Following oral intake by humans, chrysin has low bioavailability and rapid excretion.

Low aqueous solubility, rapid metabolism mediated by UGTs and SULT, and efficient excretion through efflux transporters including BCRP and MRP2 are the major reasons causing poor systemic bioavailability for chrysin.

The first systematic human pharmacokinetic study was particularly informative: this study supports the view that the bioavailability of chrysin, and possibly other flavonoids, in humans is very low, due to extensive presystemic intestinal metabolism. The disposition and metabolism of an oral dose of chrysin was determined in seven human volunteers using plasma, urine and stool measurements. The administration to human volunteers of 400 mg chrysin in a single dose resulted in extensive plasma binding (>99%) and oral bioavailability of 0.003–0.02%.

After absorption, chrysin is extensively converted by phase II metabolism into chrysin 7-O-sulfate and chrysin 7-O-glucuronide. Chrysin sulfate is reported as the predominant circulating metabolite, often exceeding parent chrysin concentrations by ~30-fold in vivo. These conjugates are thought to have limited biological activity, suggesting that strategies which increase systemic exposure of intact chrysin may enhance its therapeutic potential.

Chrysin dissolves poorly in bodily fluids, which is the first essential step for effective absorption. The small amount of chrysin that manages to be absorbed is immediately and extensively metabolized in the intestines and liver. This leads to the formation of inactive or much less active metabolites (glucuronides and sulfates) before the compound reaches the bloodstream.

Chrysin has poor intestinal absorption, and its maximum concentration in serum is 12 to 64 nM.

Although systemic bioavailability is very low, because of efficient enterohepatic recycling facilitated by phase II metabolism and efflux, chrysin's bioavailability in the lower GI tract is relatively high. This suggests that chrysin may have greater utility for diseases of the gastrointestinal tract than for systemic conditions.

5. Scientific Evidence by Area of Use

A critical overarching observation applies to all areas described below: most impressive results regarding chrysin's anticancer, anti-inflammatory, or neuroprotective properties come from cell line studies (in vitro) or animal models (in vivo). These studies often use high concentrations or special administration routes (e.g., injections) that bypass the bioavailability issue. However, high-quality randomized clinical trials confirming these benefits in humans after standard oral supplementation are lacking.

5.1 Testosterone Enhancement and Aromatase Inhibition

Chrysin is popular among athletes and bodybuilders as a purported natural aromatase inhibitor, meant to block the conversion of testosterone to estrogen. However, clinical studies in humans have not confirmed this efficacy. Oral intake of chrysin was shown not to significantly affect estrogen or testosterone levels, which directly results from its minimal bioavailability.

As of 2016, there was no clinical use of chrysin, and no evidence for its effect on testosterone levels. Research showed that orally administered chrysin does not have clinical activity as an aromatase inhibitor.

One clinical study examined urinary testosterone levels: Gambelunghe et al. performed a study to examine the effect of chrysin on urinary testosterone levels in human males aged 25–30 years. The results of that study did not demonstrate the in vitro aromatase inhibition translating into clinically meaningful hormonal changes, consistent with the bioavailability problem.

Evidence strength: In vitro evidence of aromatase inhibition is well established; however, human clinical evidence is negative. The discrepancy is attributed to near-zero oral bioavailability of chrysin.

5.2 Anxiety and Central Nervous System Effects

The pharmacological effects of 5,7-dihydroxyflavone (chrysin), a naturally occurring monoflavonoid that displaces [³H]flunitrazepam binding to the central benzodiazepine (BDZ) receptors, were examined in mice. In the elevated plus-maze test of anxiety, diazepam (0.3–0.6 mg/kg) or chrysin (1 mg/kg) induced increases in the number of entries into the open arms and in the time spent on the open arms, consistent with an anxiolytic action of both compounds. The effects of chrysin on the elevated plus-maze were abolished by pretreatment with the specific BDZ receptor antagonist Ro 15-1788 (3 mg/kg). These data suggest that chrysin possesses anxiolytic actions without inducing sedation and muscle relaxation.

A study in laboratory rats investigated the potential anxiolytic effects of chrysin, a Passiflora extract, and the purported modulation of the benzodiazepine receptor on the GABA(A) receptor. The researchers hypothesized that chrysin decreases anxiety via interaction with the GABA(A) receptor, as measured by elevated plus-maze, corticosterone, and catecholamine assays. Forty-four male Sprague-Dawley rats were randomized in a double-blind, placebo-controlled, between-subjects experimental design. Each animal received an intraperitoneal injection of vehicle, chrysin at 2 mg/kg, midazolam at 1.5 mg/kg, or flumazenil at 3 mg/kg and chrysin at 2 mg/kg.

Flavonoid components, particularly chrysin and apigenin, have been shown to selectively bind to the benzodiazepine (BZ) site on GABA receptors.

A scoping review systematically analyzed 29 studies published between 2005 and 2023, identified through a search of PubMed, Scopus, and Web of Science databases. This study highlights the significant neuroprotective potential of chrysin, particularly in its ability to modulate key inflammatory and oxidative stress pathways across various neuroinflammatory and neurodegenerative models. Chrysin has effectively inhibited critical inflammatory mediators, such as NF-κB, iNOS, and COX-2, while enhancing antioxidant defenses.

Evidence strength: Preclinical (animal) data for anxiolytic activity are consistent and mechanistically plausible, involving well-characterized GABA-A receptor benzodiazepine-binding site interactions. No controlled human clinical trials isolating chrysin as the anxiolytic agent exist to date; clinical evidence for anxiolytic effects derives from passionflower whole-plant extract trials, not from isolated chrysin.

5.3 Anticancer Activity

Several in vitro and in vivo studies have shown potential anti-cancer effects of chrysin in breast cancer, prostate cancer, lung cancer, and others. The anticancer effects of chrysin are attributed to its ability to interfere with the signalling pathways associated with inflammation and apoptosis.

In bladder cancer cells, chrysin provoked apoptosis due to activation of caspases-3 and 9, reduced Bcl-2, Mcl-1, and Bcl-xl expression, and promoted Bax protein expression. Chrysin also induced ER stress via activation of the unfolded protein response of PRKR-like ERK, eIF2α, and activating transcription factor 4.

Its role in various cancers has been demonstrated, and it modulates cell signaling pathways, including inflammation, angiogenesis, apoptosis, autophagy, and the cell cycle.

Evidence strength: Predominantly in vitro and animal evidence. No robust human clinical trials establishing chrysin as an effective anticancer treatment exist. The clinical translation is significantly limited by poor oral bioavailability.

5.4 Anti-inflammatory Effects

Chrysin demonstrates anti-inflammatory action through several mechanisms: it suppresses cyclooxygenase-2 (COX-2), an enzyme involved in prostaglandin synthesis that promotes inflammation; it inhibits phosphorylation and degradation of IκB-α, as well as the translocation of NF-κB, and reduces levels of TNF-α and IL-1β by inhibiting NF-κB expression.

Chrysin prevented the release of NO and pro-inflammatory cytokines including TNF-α and IL-1β, and the expressions of iNOS and COX-2 via inhibiting the activations of signaling molecules involved in neuroinflammation (c-Jun N-terminal kinase and NF-κB).

Evidence strength: In vitro and animal model data are robust. Human clinical data are absent.

5.5 Neuroprotection and Neurological Disorders

Among family members of the flavonoid class, chrysin appears as a promising natural flavonoid, exhibiting an array of neuroprotective effects by attenuating oxidative stress, neuroinflammation, and apoptosis.

Treatment with chrysin was shown to reduce TBI-induced oculomotor dysfunction and memory impairment by inhibiting neuroinflammation and apoptosis via the upregulation of the Bcl-2 family and the downregulation of the Bax protein. In another study, chrysin supported the alleviation of TBI-related anxiety and depression-like behavior. Furthermore, treatment with chrysin (10 and 20 mg/kg) was demonstrated to reduce brain edema after ischemic stroke.

Chrysin mitigates neuroinflammation by inhibiting NF-κB signaling, downregulating pro-inflammatory cytokines (TNF-α, IL-6, IL-1β), and suppressing the expression of COX-2 and iNOS.

Evidence strength: Exclusively preclinical (animal and in vitro). No human RCTs. Findings are mechanistically consistent and promising but require clinical validation.

5.6 Antidiabetic Effects

Chrysin, a naturally occurring flavone most abundantly found in numerous plants including fruits and vegetables, possesses potent anti-diabetic, anti-inflammatory, and antioxidant activities. Positive effects of chrysin on browning of fat and obesity have also been reported.

In vitro studies in antidiabetic research have demonstrated that chrysin and its nanoformulation exhibited anti-diabetic and antiglycating activities in a dose-dependent manner, and the nanoform of chrysin acts as a better antidiabetic and antiglycating agent compared to its bulk form.

Evidence strength: Preclinical evidence (in vitro and animal). No published human RCTs specifically evaluating chrysin for diabetes management. Mechanistic data via alpha-amylase and alpha-glycosidase inhibition are promising but unconfirmed clinically.

5.7 Cardioprotective Effects

Oxidative stress undoubtedly contributes to the development of cardiovascular diseases such as atherosclerosis, hypertension, and cardiomyopathies, making antioxidant flavonoids such as chrysin of interest.

In one animal study, pre-treatment of chrysin restored the effect of ischemic preconditioning in ischemia/reperfusion injury in relation to an increase in activities of SOD and CAT, along with a reduction in LPO level in diabetic-challenged rat hearts. Chrysin was given via oral route at a dose of 60 mg/kg for a week before the isolation of the heart in the experimental protocol.

Evidence strength: Animal-model data only. No human clinical trials. The dose used in rat studies (60 mg/kg) does not directly translate to human supplementation regimens.

5.8 Hepatoprotective Effects

Hepatoprotective effects of chrysin against ethanol on the alteration of alcohol-metabolizing enzymes — alcohol dehydrogenase (ADH), cytochrome P450 2E1 (CYP 2E1), and xanthine oxidase (XO) — and oxidant/antioxidant status were observed in rats. Chrysin administration prevented liver damage during chronic ethanol consumption by modulating the activities of ADH, CYP 2E1, XO, and CAT enzymes in rats.

Chrysin supplementation protected the liver against PhIP-induced mutagenic effects by inducing UDP-glucuronosyltransferase and/or inhibiting sulfotransferase in HepG2 cells.

Evidence strength: Animal and in vitro data. No human trials.

5.9 Protective Effects Against Toxic Agents

A growing body of scientific evidence has shown that chrysin possesses protective effects against toxic agents in various animal tissues, including brain, heart, liver, kidney, and lung. This evidence may indicate effectiveness in disease management induced by toxic agents; however, due to the lack of information in humans, further studies are needed to determine the efficacy of chrysin as an antidote agent in humans.

5.10 Gastrointestinal Application: Irinotecan-Induced Diarrhea

One area where human clinical investigation has occurred is the use of chrysin to modulate intestinal glucuronidation. Clinical studies have been conducted using chrysin to modulate UGTs in the GI tract to prevent irinotecan-induced diarrhea. The results showed that systemic exposure of SN-38 was not altered significantly when chrysin was combined with irinotecan, but diarrhea severity appears to be reduced. These findings may reveal that UGT1A1, the enzyme catalyzing SN-38 metabolism, was only regulated in the intestine but not in the liver by chrysin. If this hypothesis is correct, chrysin could have higher distribution in the GI tract to exert better UGT1A1 regulation when compared to the liver and other organs.

Evidence strength: This is one of the few areas where human clinical use of chrysin has been studied, exploiting its relatively higher local bioavailability in the gut. Results are preliminary and require further investigation.

6. Body Systems and Health Areas of Association

Chrysin has anti-cancer, anti-viral, anti-diabetic, neuroprotective, cardioprotective, hepatoprotective, and renoprotective as well as gastrointestinal, respiratory, reproductive, ocular, and skin protective effects through modulating signaling pathways involved in apoptosis, oxidative stress, and inflammation.

• Endocrine / Reproductive system: Inhibition of aromatase enzyme (CYP19A1) in vitro; proposed but unconfirmed role in testosterone/estrogen balance.
• Central Nervous System: Neuroprotective effects through anti-oxidant, anti-inflammatory and anti-apoptotic functions, MAO inhibition, and GABA mimetic properties.
• Cardiovascular system: Antioxidant protection against ischemia-reperfusion injury; anti-fibrotic activity in preclinical models.
• Gastrointestinal system: Local UGT modulation with potential to reduce chemotherapy-associated diarrhea; relatively higher local bioavailability in the lower GI tract.
• Immune / Inflammatory system: Suppression of NF-κB, COX-2, iNOS, TNF-α, and interleukins across multiple cell and animal models.
• Oncology: Preclinical antiproliferative, pro-apoptotic, and anti-angiogenic activity across multiple cancer cell lines.
• Metabolic / Endocrine (diabetes): Alpha-glucosidase inhibition and glycation reduction in vitro; AMPK/AKT/PPAR pathway modulation in animal models.
• Hepatic / Renal systems: Protective effects against chemical and drug-induced organ damage in animal models.

7. Dosage Forms and Dosages Reported in Studies

The following dosages appear in the referenced scientific literature. They are reported descriptively as found in studies and do not constitute recommendations.

• A single oral dose of 400 mg of chrysin was administered to human volunteers in a pharmacokinetic study to describe its oral disposition.
• In a rat anxiolytic study (intraperitoneal), chrysin was administered at 2 mg/kg, compared to midazolam at 1.5 mg/kg and flumazenil at 3 mg/kg.
• In the elevated plus-maze test in mice, chrysin at 1 mg/kg was found to produce anxiolytic effects comparable to diazepam at 0.3–0.6 mg/kg.
• Chrysin at 10 and 20 mg/kg was demonstrated to reduce brain edema after ischemic stroke in animal models.
• In a rat cardioprotection study, chrysin was given via oral route at a dose of 60 mg/kg for one week.
• Administration of chrysin at 20 mg/kg bodyweight exerted antioxidant activities to prevent D-galactose-mediated aging in rats.
• Oral supplementation of chrysin at 100 mg/kg body weight decreased ammonium chloride-induced neuroinflammatory responses in rats.

While its therapeutic potential appears promising, challenges such as low bioavailability and limited clinical data highlight the need for more in-depth investigation. The gap between animal-model doses and any achievable human plasma concentration — given near-zero oral bioavailability — is a central limitation to the clinical interpretation of all dosage data from animal studies.

8. Safety Considerations and Interactions

8.1 General Safety Profile

As of 2016, there was no toxicity attributable to chrysin in clinical trials or adverse event reporting, and clinical safety issues had not been identified. As of 2016, however, nonclinical data suggest potential concerns.

8.2 Mutagenicity Findings

One study raised important caution: the micronucleus test showed that from 1 to 15 μM of chrysin, mutagenic activity was noted in HepG2 cells. The Salmonella assay demonstrated a positive response to the TA100 Salmonella strain in the presence or absence of S9, suggesting that this compound acted on DNA, inducing base pair substitution before or after metabolism via cytochrome P-450. These results showed that chrysin is a mutagenic and cytotoxic compound in cultured human HepG2 cells and Salmonella typhimurium. These are in vitro findings and their relevance to human exposure at typical dietary or supplemental levels is unknown.

8.3 Cytochrome P450 Interactions

Being metabolized by the same enzymes as many drugs (cytochrome P450), chrysin theoretically could interact by affecting their concentration and action. Although this risk is low with standard supplementation (due to poor absorption), it may become relevant when advanced delivery systems are used that increase blood concentrations.

Chrysin inhibited CYP1A1/2 and CYP3A activities in rat and human liver microsomes. However, in a rat pharmacokinetic interaction study, the pharmacokinetic parameters for caffeine and its three metabolites (paraxanthine, theobromine, and theophylline) were not changed following chrysin treatment in vivo, despite its inhibitory effect on CYP1A in vitro. This illustrates that in vitro CYP inhibition by chrysin does not necessarily produce clinically meaningful in vivo drug interactions due to poor systemic bioavailability.

8.4 Regulatory Status

In 2016, the US Food and Drug Administration did not recommend chrysin be included on the list of bulk drug substances that can be used in compounding under section 503A of the Federal Food, Drug, and Cosmetic Act, based on consideration of the following criteria: (1) physicochemical characterization; (2) safety; (3) effectiveness; and (4) historical use of the substance in compounding. Chrysin dietary supplements are not subject to the strict controls applied to drugs.

8.5 Bioavailability Enhancement and Emerging Safety Considerations

The development of novel nanoformulations that substantially increase chrysin's bioavailability introduces new safety considerations. Being metabolized by the same enzymes as many drugs (cytochrome P450), chrysin theoretically could interact by affecting their concentration and action. Although this risk is low with standard supplementation (due to poor absorption), it may become relevant when advanced delivery systems are used that increase blood concentrations.

Chrysin is a known CYP2E1 and CYP3A4 inhibitor, and this inhibitory activity is relevant to the bioactivation of co-administered drugs such as paracetamol to NAPQI. This interaction has been explored in rats but has not been fully characterized in humans.

9. Research Gaps and Current Status

Most impressive results regarding chrysin's anticancer, anti-inflammatory, or neuroprotective properties come from cell line studies (in vitro) or animal models (in vivo). These studies often use high concentrations or special administration routes (e.g., injections) that bypass the bioavailability issue. However, high-quality randomized clinical trials confirming these benefits in humans after standard oral supplementation are lacking.

Despite its well-documented biological activities, chrysin's low water solubility and bioavailability hinder its clinical development. Research is exploring the application of nanocarriers as a strategic approach to overcome these challenges and enhance the delivery of chrysin. Nanocarriers, including polymer-based nanoparticles (NPs), lipid-based NPs, and inorganic nanocarriers, have shown promise in improving the solubility, bioavailability, and tumor-targeted delivery of chrysin.

As of 2016, there is no evidence for chrysin being used in human clinical applications. While this assessment predates recent clinical pharmacokinetic work — notably the micellar formulation trial demonstrating a 2–3-fold increase in exposure — the absence of human efficacy RCTs for any indication remains a fundamental gap in chrysin research as of the available literature.

References

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