Phlorizin

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1. What Phlorizin Is and How It Works

Phlorizin is a secondary plant compound from the dihydrochalcone group, chemically a glycoside of phloretin. It is primarily found in apples (Malus domestica), particularly in the peel, seeds, and leaves, and in smaller quantities in other members of the rose family such as pears or quinces. In the plant, it acts as a defence compound against pathogens and regulates carbohydrate metabolism. Its pharmacological significance arose from the discovery that it inhibits the reabsorption of glucose in the kidneys—a mechanism that later led to the development of SGLT2 inhibitors, a key class of antidiabetic agents.

The key mechanism of action of phlorizin is the competitive inhibition of sodium-glucose cotransporters (SGLT1 and SGLT2). SGLT2 is primarily located in the kidneys and is responsible for approximately 90% of glucose reabsorption from the primary urine, while SGLT1 in the gut and, to a lesser extent, in the kidneys absorbs glucose from food. Phlorizin binds to these transporters, blocking active glucose transport, which results in increased glucose excretion via urine. This effect was first demonstrated in animal models and later in human cell cultures. However, the bioavailability of phlorizin is low, as it is hydrolysed in the gut by β-glucosidases into phloretin, which itself has a weaker inhibitory effect on SGLT1.

2. What the Studies Show in Detail

The pivotal human studies and key reviews—by application area, including population, duration, preparation, measured parameters, and results, as reported in the original works. Numbers are only included where the study provides them.

Distribution of controlled human studies by application area—the numbers are not additive, as one study may be assigned to multiple areas:

Oncology

Confirmed: Phlorizin, a natural SGLT inhibitor, was first discovered in 1835 and serves as the basis for the development of specific SGLT2 inhibitors used in diabetes therapy. A controlled study (2013) on SGLT2 inhibitors such as canagliflozin, dapagliflozin, and empagliflozin—when used as monotherapy in diabetic patients—showed reductions in HbA1c levels (0.34% to 1.03%), body weight (2.0 to 3.4 kg), and blood pressure (systolic: 1.7 to 6.4 mmHg; diastolic: 0.3 to 2.6 mmHg). These findings apply to synthetic SGLT2 inhibitors, not phlorizin itself. The review article (2022) confirms that phlorizin, as a bioactive component in apples (alongside procyanidins and chlorogenic acid), may contribute to preventive potential against chronic diseases such as cancer, although the precise mechanisms in oncology have yet to be clinically investigated.

Plausible The preventive effect of phlorizin against cancer is attributed in preclinical studies to its antioxidant and anti-inflammatory properties, observed in vitro and in animal models. Since SGLT2 inhibitors demonstrate cardiovascular benefits in humans, similar signalling pathways may be relevant in tumour biology—potentially through inhibition of the Warburg effect or modulation of the tumour microenvironment. However, these mechanisms remain unconfirmed in humans, and controlled studies are needed to determine whether phlorizin or its derivatives exert a direct antitumour effect. The review emphasises that the bioavailability of phlorizin is influenced by the food matrix (e.g., apple consumption), which complicates the translation of preclinical data to humans.

Hypothesis If the hypothesis that SGLT inhibition is relevant beyond diabetes control—including in oncology—is confirmed, phlorizin could serve as a lead structure for dual SGLT1/2 inhibitors that influence both metabolic and proliferative signalling pathways. Combining it with established therapies (e.g., checkpoint inhibitors) might be a viable approach to exploring immunomodulatory effects. However, current studies focus on diabetes and cardiovascular endpoints, and systematic investigation in oncology remains outstanding.

Gut and Microbiome

Observed in preclinical and human settings: The controlled study 2 (2023) investigated the interindividual variability in phloretin metabolism following apple consumption in 62 participants. After acute and 6-week administration of 80 g freeze-dried apple snacks (low vs. high phloretin content: 39.5 µmol vs. 103 µmol), absorption varied up to 70-fold (0.1% to 6.94% of ingested phloretin glycosides). In 74% of participants, phloretin-O-glucuronide emerged as the dominant metabolite, particularly at higher phloretin intake and among 'high-producers'. Women more frequently exhibited a glucuronide profile (64.1%), whereas men were more commonly assigned to the 'low-excretion' group. The study also observed a trend towards moderate changes in blood glucose and insulin levels among high-producers after 6 weeks, though these findings do not establish a clinical effect. 5 (2016) demonstrated in mini-pigs that bile diversion following Roux-en-Y gastric bypass (RYGB) reduces sodium-dependent glucose uptake in the alimentary limb (AL). This effect was restored by adding bile or sodium and blocked by phlorizin, highlighting the central role of SGLT1 in the intestine.

Plausible The review articles 26 (2018) and 29 (2019) show that SGLT1 is responsible for intestinal glucose uptake, while SGLT2 primarily acts in the kidney. Phlorizin inhibits both transporters, which explains the observed effects in 5. The interindividual variability in 2 may stem from genetic polymorphisms (e.g., in UGT or SULT enzymes) or differences in the gut microbiome, which is involved in polyphenol metabolism. A study (2014) identified genetic variants of lactase-phlorizin hydrolase (LCT) associated with lactase persistence, though a direct link to phloretin metabolism or clinical outcomes was not established in this work.

Hypothesis The findings from 2 suggest that 'phloretin metabotypes' may exist, influencing the efficacy of apple polyphenols. If confirmed that high-producers benefit more from blood glucose-lowering effects, personalised dietary recommendations could be feasible. Additionally, combining phlorizin with probiotics that enhance glucuronidation might improve bioavailability. However, studies systematically testing these hypotheses—particularly regarding long-term effects on the microbiome and glucose homeostasis—are lacking.

Metabolism

Plausible The observational study 6 (2015) tested the acute antihyperglycaemic effect of a phlorizin-rich apple powder (12.61 g/kg phlorizin) from unripe apples in six healthy participants. In the oral glucose tolerance test (OGTT), the preparation reduced the postprandial blood glucose increase by approximately 50% (p < 0.05) at 15–30 minutes and increased renal glucose excretion fivefold (p < 0.05) in the 2–4-hour interval. Study 3 (2021) describes that SGLT2 inhibitors reduce glucose reabsorption in the renal tubules by 50–60%, which has been shown to lower HbA1c levels in type 2 diabetes. 4 (2015) further demonstrated in vitro that phlorizin and canagliflozin dose-dependently inhibit NO-dependent vasorelaxation in pulmonary arteries (but not coronary arteries) by blocking SNP-induced membrane hyperpolarisation in smooth muscle cells.

Plausible The effects observed in 6 can be attributed to SGLT1/2 inhibition by phlorizin, which reduces both intestinal glucose uptake and renal reabsorption. Study 7 (2017) suggests that SGLT2 is also expressed in mesangial cells and retinal pericytes and may contribute to the pathogenesis of diabetic nephropathy and retinopathy. Phlorizin mitigated hyperglycaemia-induced dysfunction in these cells in vitro, indicating a potential protective effect in preclinical models; clinical studies in humans are required to determine whether this translates to therapeutic benefits. The review (2016) summarises that phlorizin, as a natural SGLT inhibitor, inspired the development of synthetic SGLT2 inhibitors now used as standard therapy for diabetes.

Hypothesis The differing effects of phlorizin on pulmonary versus coronary arteries in 4 may reflect tissue-specific expression of SGLT isoforms or signalling pathways. If confirmed in vivo that SGLT2 inhibition directly influences vascular complications in diabetes, targeted therapies could be developed. However, clinical studies validating these effects in humans—particularly regarding long-term impacts on vascular function and organ damage—are lacking.

Inflammatory Processes

Proven The review (2021) describes phloridzin (phlorizin) as a dihydrochalcone with diverse pharmacological effects, including anti-inflammatory, antioxidant, and immunomodulatory properties. Extraction is primarily from plants of the Malus genus (e.g., apple tree bark) using high-speed countercurrent chromatography (HSCCC) or preparative HPLC. Phlorizin’s bioavailability is low, as it is metabolised to phloretin in the intestine. 30 (2017) shows that consuming whole apples (compared to isolated polyphenols) has synergistic effects on cardiovascular risk factors in preclinical assessments, including inflammatory markers such as CRP. The study attributes this to the interaction of phlorizin with fibre and other polyphenols, which enhances bioavailability and bioactivity in preclinical settings.

Plausible The anti-inflammatory effects of phlorizin, as described in preclinical studies, are linked to the inhibition of NF-κB signalling pathways and the reduction of pro-inflammatory cytokines (e.g., TNF-α, IL-6), demonstrated in cell cultures and animal models. The review 30 emphasises that the food matrix (e.g., apple consumption) improves phlorizin’s bioavailability, supporting the plausibility of these mechanisms. However, controlled human studies directly measuring these effects—particularly dose-response relationships and long-term outcomes—are lacking.

Hypothesis If confirmed that phlorizin modulates inflammatory pathways to influence chronic conditions such as rheumatoid arthritis or neurodegenerative processes, it could serve as an adjuvant therapy. Combining it with other polyphenols (e.g., quercetin) or probiotics that strengthen the gut barrier is a conceivable approach.

Overall Picture

Proven Phlorizin is a well-characterised natural inhibitor of sodium-glucose cotransporters (SGLT1/2) with proven effects on glucose metabolism. Studies 3, 6, and 8 demonstrate that phlorizin and its synthetic derivatives (e.g., canagliflozin) increase renal glucose excretion, lower blood glucose, and offer additional metabolic benefits such as weight reduction and blood pressure lowering. The interindividual variability in phloretin metabolism (2) points to complex pharmacokinetic processes influenced by enzyme polymorphisms and the food matrix. In preclinical oncology and inflammation research (e.g., 30), phlorizin has shown antioxidant, anti-inflammatory, and potentially antitumour properties in animal and cell culture models, though these effects have not been investigated in humans.

Open Questions: While the metabolic effects of phlorizin and SGLT inhibitors are well documented, systematic studies on their roles in oncology, inflammation, and microbiome modulation are lacking. The translatability of preclinical data to humans is limited by phlorizin’s low bioavailability, and controlled human studies on long-term effects (e.g., on vascular function or tumour progression) are absent. Additionally, it remains unclear whether the observed interindividual differences in metabolism (2) are clinically relevant and could enable personalised applications. Research into combination strategies (e.g., with probiotics or other polyphenols) may open new therapeutic avenues.

3. How Robust Is the Research?

Research on phlorizin is heavily basic-science oriented: Of the 176 evaluated studies, 82 are basic research, 31 are cell culture studies, and only 22 involve human participants. The two controlled human studies focus on metabolism and bioavailability, while observational studies primarily examine metabolic effects and genetic variability. The most cited works stem from mechanistic research (e.g., the development of SGLT inhibitors) and plant biosynthesis. Notably, while phlorizin is studied as a natural compound, its pharmacological relevance lies primarily in inspiring synthetic derivatives now used as diabetes medications.

Methodologically, the field is heterogeneous: Its strength lies in the detailed elucidation of molecular mechanisms, particularly SGLT inhibition, well-supported by cell culture and animal studies. Its weakness is the translatability to humans: Only two controlled studies exist, and these do not assess clinical endpoints (e.g., long-term metabolic effects), instead focusing on pharmacokinetics and metabolite profiles. Most human studies are observational and examine associations (e.g., between apple consumption and metabolic markers), not causal effects. The question of phlorizin’s clinical relevance—beyond its role as a template for SGLT2 inhibitors—thus remains open.

4. What Is Often Claimed—and What the Data Show

5. Fact Sheet: Molecule and Charge

Phlorizin is not a single molecule but a mixture—there is no molecular formula or fixed molecular mass. What can be described are functional groups, charge behaviour, and redox properties, which are the focus of the next section.

6. Charge, Electrons, Radicals

Electrochemical Properties of Phlorizin: Radical Scavenging and Redox Modulation In human cell models, phlorizin demonstrates a pronounced ability to neutralise reactive oxygen species (ROS). In HepG2 cells, apple-derived phlorizin (100–150 µg/ml) reduced ROS production, thereby mitigating oxidative stress, apoptosis, and DNA damage 15 18. This effect correlates with strong radical-scavenging activity, measured in DPPH and ABTS assays: extracts containing phlorizin achieved antioxidant capacity comparable to ascorbic acid 16 17. Quantitatively, radical-scavenging performance in enriched samples increased by up to 26.68% (DPPH) and 32.98% (α-glucosidase inhibition). The redox properties are attributed to the high polyphenol and flavonoid content, confirmed in ferric ion reduction assays (FRAP) 17. Additionally, interactions with signalling pathways were investigated: phlorizin modulated ROS-mediated activation of NF-κB in cell cultures and reduced the expression of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) as well as angiogenic factors (VEGF, MMP2/9) 20. Whether these effects result from direct electron transfer or indirect signal modulation remains to be clarified. The next step would be to determine whether phlorizin exhibits comparable redox potential in vivo and whether the observed cytoprotective effects are dose-dependently reproducible.

Plausible The available data are currently limited to indirect evidence: radical-scavenging activity correlates with the structural availability of hydroxyl groups in polyphenols 17 19, suggesting involvement of proton or electron donor mechanisms. In vitro, phlorizin demonstrated efficacy comparable to synthetic antioxidants (BHT, TBHQ) (EC50: 2.92 mg/L) 19. It remains unclear whether phlorizin acts as a redox buffer in biological systems or specifically chelates metal ions (e.g., Fe³⁺). Animal or human studies on bioavailability and metabolism could clarify whether the effects observed in cell cultures 16 are reproducible at the systemic level. The next step would involve electrochemical characterisation using cyclic voltammetry or ESR spectroscopy to directly quantify charge dynamics and radical interactions.

7. Interactions with Other Substances

Substances with which this compound has been jointly investigated or discussed in human studies and review articles on this platform—whether in combination, comparison, or via shared mechanisms. The number indicates studies in which both appear.

CYP3A4 exhibits a 3.3-fold lower Michaelis constant (K_m) than CYP2C19, indicating higher affinity. The catalytic efficiency of CYP3A4 is 1.8-fold greater than that of CYP2C19 21, and antibodies against CYP3A4 inhibit up to 90% of microsomal phloretin-3-hydroxylation, whereas anti-CYP2C19 shows significantly weaker effects 21 21. CYP3A4 thus plays a major role in the metabolism of phloretin in human liver microsomes 21. Phloretin also inhibits CYP3A4-mediated testosterone-6β-hydroxylation 21, suggesting potential interactions with CYP3A4 substrates. The productivity of the biotransformation of phloretin to 3-OH-phloretin by CYP3A4 is 0.16 mM h^-1 under optimal conditions 21.

Interactions with other substances: Phlorizin (Phd) showed no effect in combination with substance S, while 4-methylchalcone (4-MeCh), alone or combined with S, exhibited enhanced inhibitory effects—particularly in the context of cancer therapeutics 23. Phloretin also interacts with taste receptors: lactisole, an antagonist of the TAS1R2/R3 receptor, completely inhibits the taste response to glucose (≤250 mM) at a concentration of 1 mM 22. It remains unclear whether phlorizin or phloretin influences the absorption or efficacy of other nutrients (e.g., glucose) or pharmaceuticals (e.g., GABA_A receptor modulators such as betulin 10). The next step would be to determine whether the observed enzyme inhibitions and receptor interactions result in clinically relevant interactions—particularly with concurrent use of CYP3A4 substrates or antidiabetic agents.

8. Overdose, Tolerability, Limitations

Evidence-based: Adverse effects and toxicity of phlorizin in human studies Phlorizin, a natural inhibitor of SGLT1 and SGLT2 transporters, was not clinically adopted due to its short half-life and intestinal side effects 26. Safety concerns, such as a potential increased risk of urinary tract infections or cancers (breast, bladder) with dapagliflozin, remained unconfirmed and were attributed to pre-existing conditions 25. The poor oral bioavailability of phlorizin itself precluded its clinical use, restricting it to physiological investigations 24. Plausible: Cytotoxicity in tissue and cell models In human cell lines (melanoma A375, epidermoid carcinoma A431, non-tumour HaCaT cells), a phlorizin derivative (PZDHA) demonstrated cytotoxic effects 27. The addition of ascorbic acid/α-tocopherol fully reversed cytotoxic effects in other tissues. A docosahexaenoic acid ester of phloridzin enhanced cytotoxicity across all tested cell lines 27. In HT29 cells (a colorectal cancer model), non-toxic doses of 30 µM phlorizin equivalents were used to analyse gene expression patterns 28. The next step would be to assess whether the cytotoxicity observed in cell cultures occurs in a dose-dependent manner and whether these effects can be reproduced in vivo.

Hypothesis: Potential contraindications and upper limits As phlorizin itself is not used clinically, direct data on upper limits or contraindications are lacking. However, derived SGLT2 inhibitors are considered safe and effective in older adults without requiring aggressive interventions. Reviews highlight adverse effects of other antidiabetic agents, such as hypoglycaemia, weight gain, or hepatorenal toxicity—a context that drove the search for safer alternatives like SGLT2 inhibitors. Evidence-based: Lack of clinical relevance of phlorizin Due to its pharmacokinetic limitations (low bioavailability, intestinal side effects), phlorizin remained a physiological tool 24 26. Post-harvest practices in apples (the primary source of phlorizin) were examined for storage safety but did not yield direct toxicity data. In cell cultures, phlorizin derivatives like Q3G exhibited dose- and time-dependent cytotoxic effects in HeLa cells, while UV-C irradiation of apple juice affected polyphenols and vitamins without specific toxicity analyses for phlorizin. The next question is whether structural modifications of phlorizin (e.g., esters) could improve bioavailability while minimising the side-effect profile.

9. The Most Robust Studies

Ranked by evidential strength, not by prominence. The full evaluation includes significantly more studies; here, only the most reliable are listed.

Controlled Human Studies

• 1 SGLT-2 inhibitors and their potential in the treatment of diabetes (2013)
• 2 Assessment of human inter-individual variability of phloretin metabolites in urine after apple consumption. AppleCOR study (2023)

Observational Human Studies

• Genetic origins of lactase persistence and the spread of pastoralism in Africa (2014)
• 3 SGLT2 Inhibitors: Physiology and Pharmacology (2021)
• 4 SGLT inhibitors attenuate NO-dependent vascular relaxation in the pulmonary artery but not in the coronary artery (2015)
• 5 Bile Diversion in Roux-en-Y Gastric Bypass Modulates Sodium-Dependent Glucose Intestinal Uptake (2016)
• 6 Acute anti-hyperglycaemic effects of an unripe apple preparation containing phlorizin in healthy volunteers: a preliminary study (2015)
• 7 Sodium glucose cotransporter 2 in mesangial cells and retinal pericytes and its implications for diabetic nephropathy and retinopathy (2017)
• Transport and inhibition mechanism of the human SGLT2-MAP17 glucose transporter (2024)
• 8 Phlorizin Exerts Direct Protective Effects on Palmitic Acid (PA)-Induced Endothelial Dysfunction by Activating the PI3K/AKT/eNOS Signaling Pathway and (2018)
• Renal glucose transporters: novel targets for hyperglycemia management (2010)
• 9 Phlorizin, a novel caloric restriction mimetic, stimulates hypoxia and protects cardiomyocytes through activating autophagy via modulating the Hif-1α/ (2024)
• Sodium-glucose co-transporter 2 inhibitors: from apple tree to 'Sweet Pee' (2010)
• Regioselective Hydroxylation of Phloretin, a Bioactive Compound from Apples, by Human Cytochrome P450 Enzymes (2020)
• 10 Pharmacological research on natural substances in Latvia: Focus on lunasin, betulin, polyprenol and phlorizin (2016)
• 11 Competitive inhibition of SGLT2 by tofogliflozin or phlorizin induces urinary glucose excretion through extending splay in cynomolgus monkeys (2014)
• Sodium-dependent glucose co-transport proteins (SGLTs) are not involved in human glucose taste detection (2024)
• The use of SGLT2 inhibitors in older people: What is important? (2025)
• 12 Inhibition of renal glucose reabsorption as a novel treatment for diabetes patients (2014)
• Effects of apples (<i>Malus domestica</i>) and their derivatives on metabolic conditions related to inflammation and oxidative stress and (2025)
• 13 Phloridzin as a Nutraceutical for Cancer Prevention and Therapy: A Comprehensive Review of Its Mechanisms, Bioavailability Challenges and Future Applications (2025)

Studies on Human Tissue

• Polyphenols and phenolic acids from strawberry and apple decrease glucose uptake and transport by human intestinal Caco-2 cells (2010)
• Dihydrochalcone Compounds Isolated from Crabapple Leaves Showed Anticancer Effects on Human Cancer Cell Lines (2015)
• 14 Phlorizin from Lithocarpus litseifolius [Hance] Chun ameliorates FFA-induced insulin resistance by regulating AMPK/PI3K/AKT signalling pathway (2024)

10. Summary

Proven Phlorizin is a well-characterised inhibitor of sodium-glucose cotransporters (SGLT1/SGLT2), with its effects on glucose metabolism substantiated by controlled human studies and synthetic derivatives (e.g., SGLT2 inhibitors). It increases renal glucose excretion and lowers blood glucose levels. In preclinical models, phlorizin shows antioxidant and anti-inflammatory properties, and potentially antitumour effects in cell cultures and animal studies, though these effects remain unconfirmed in humans.

Plausible The inhibition of SGLT1/2 by phlorizin accounts for the observed effects on glucose metabolism and intestinal function. Its anti-inflammatory action may stem from modulation of NF-κB signalling pathways and reduction of pro-inflammatory cytokines. Hypothesis: Should it be confirmed that phlorizin exerts oncological or anti-inflammatory effects beyond diabetes control, it could serve as a lead structure for dual SGLT1/2 inhibitors or adjuvant therapies. Combining it with probiotics or other polyphenols might enhance bioavailability and enable personalised applications.

The next step would be to clarify the clinical relevance of phlorizin beyond its role as a template for SGLT2 inhibitors. Systematic human studies on its long-term effects on vascular function, tumour progression, or chronic inflammation are still pending. Additionally, interindividual variability in metabolism requires further investigation to develop personalised dosages or combination strategies (e.g., with probiotics). The translatability of preclinical data to humans remains a key open question.

11. Open Questions

• Dose-response relationship: What quantity of phlorizin is required to achieve a clinically relevant SGLT2 inhibition in humans?
• Long-term effects: Are there side effects (e.g., electrolyte imbalances) or drug interactions associated with regular intake?
• Formulations: Can pharmaceutical optimisations (e.g., enteric-coated capsules) improve bioavailability and enhance therapeutic relevance?

12. Further Paths

Topics, mechanisms, and pathways involving this compound—for those who wish to explore beyond the substance itself.

• Interaction network

Topics, mechanisms and chains in which this substance appears — for those who want to look beyond the substance.