Phloretin (Dihydrochalcone · GLUT Inhibitor · Antioxidant · Skin)

Compound	Phloretin (2′,4,4′,6′-Tetrahydroxydihydrochalcone; Phloretin; Apple Chalcone Aglycone)
Chemical class	Polyphenol — Dihydrochalcone (chalcone with alpha-beta double bond hydrogenated; unique to Malus and Pyrus species)
CAS	60-82-2
Primary source	Malus domestica (apple peel, root bark), Pyrus communis (pear), Fortunella spp. (kumquat)
Key applications	GLUT1/2 transporter inhibition (glucose uptake modulation); antioxidant; anti-inflammatory; skin brightening; antimicrobial
Claim strength	Moderate
Typical form	Polyphenols 75% Apple Extract (Malus domestica; phloretin co-delivered with phlorizin and chlorogenic acid); Green Apple Extract
Buy from Herbuno	Polyphenols 75% Powder (Apple Extract) | Standardized Malus domestica → Green Apple Extract Powder →

Name origin: Phloretin is named after phloroglucinol (1,3,5-trihydroxybenzene) — the A-ring component of the dihydrochalcone scaffold — with the "-etin" suffix following flavonoid naming conventions. Phloretin is the aglycone of phlorizin (phloretin-2′-O-glucoside), the characteristic dihydrochalcone of apple bark and peel. "Dihydrochalcone" denotes that the alpha,beta-double bond of a chalcone has been reduced — phloretin's alpha,beta-single bond distinguishes it from the corresponding chalcone. Traditional use: Phloretin has no direct traditional use as an isolated compound. The apple tree (Malus domestica) and apple preparations have extensive traditional use for digestive health, diarrhoea management, and as a source of pectin in various medical applications. Apple root bark — which contains phlorizin at much higher concentrations than fruit — was historically used in European folk medicine as an antipyretic and for febrile conditions. Phlorizin's glucose transporter inhibitory activity was characterised in the 19th century by physiologist Claude Bernard in kidney tubule studies — one of the earliest documented examples of a plant compound targeting a specific membrane transporter. Research trajectory: Phloretin's primary pharmacological interest lies in its GLUT (glucose transporter) inhibitory activity — it inhibits GLUT1, GLUT2, and GLUT4 competitively and non-competitively at micromolar concentrations, modulating glucose uptake across multiple tissue types. This mechanism has attracted attention for metabolic syndrome, cancer (GLUT1 overexpression in many tumours), and topical skin brightening (GLUT-dependent melanocyte glucose supply modulation). Commercial source: Phloretin is available from Herbuno via Polyphenols 75% Apple Extract and Green Apple Extract (both Malus domestica), which deliver phloretin alongside phlorizin (the glucoside precursor) and chlorogenic acid.

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Evidence for Phloretin Applications

GLUT inhibition and glucose metabolism: Phloretin inhibits GLUT1 (IC₅₀ ~0.2 μM), GLUT2 (~0.5 μM), and GLUT4 (~6 μM) — the primary glucose transporters mediating intestinal absorption, hepatic glucose efflux, and insulin-dependent muscle uptake respectively. In high-fat diet and diabetic rodent models, phloretin/phlorizin preparations reduce postprandial glucose excursion and fasting glucose, improve insulin sensitivity, and reduce HbA1c-equivalent markers. The GLUT2 inhibition in intestinal brush border reduces dietary carbohydrate absorption analogously to acarbose (alpha-glucosidase inhibition) but via a distinct mechanism. Claim strength: Moderate.

Antioxidant: Phloretin's phloroglucinol A-ring and 4-hydroxyphenyl B-ring confer good DPPH and ABTS radical scavenging capacity. Nrf2/HO-1 pathway induction is documented, providing cellular antioxidant enzyme upregulation. In comparison with other apple polyphenols (chlorogenic acid, quercetin), phloretin demonstrates comparable or superior radical scavenging at equivalent molar concentrations. Claim strength: Moderate.

Skin brightening and cosmetic applications: Phloretin inhibits tyrosinase and disrupts GLUT-mediated glucose supply to actively melanising melanocytes — two complementary depigmentation mechanisms. Clinical topical studies with phloretin-containing apple extract formulations demonstrate improvement in skin tone uniformity, hyperpigmentation reduction, and brightening comparable to kojic acid at equivalent concentrations. Phloretin's antioxidant activity additionally protects skin against UV-induced oxidative damage at the formulation level. Claim strength: Moderate (topical).

Antimicrobial and anti-inflammatory: Phloretin demonstrates antimicrobial activity against cariogenic bacteria (Streptococcus mutans — relevant to dental caries prevention) via biofilm disruption and cell membrane permeabilisation. NF-κB inhibition and TNF-α suppression in macrophage models contribute to anti-inflammatory positioning. Claim strength: Moderate (antimicrobial); Emerging (systemic anti-inflammatory).

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Dosage & Formulator Specification

No established human supplement dosing protocol exists for isolated phloretin. Apple polyphenol preparations studied for metabolic effects used 600–1200 mg/day standardised apple extract (delivering phloretin + phlorizin + chlorogenic acid + quercetin glycosides) over 4–12 weeks — phloretin representing approximately 5–10% of total apple polyphenol extract. For topical skin brightening, phloretin-containing apple extract formulations at 0.5–2% concentration in serum/cream are commercially used.

Polyphenols 75% Apple Extract from Herbuno delivers phloretin alongside phlorizin (the 2′-O-glucoside, which is hydrolysed in the gut to phloretin) and chlorogenic acid. At 200 mg of 75% polyphenol extract, approximately 5–15 mg phloretin is delivered depending on the apple polyphenol profile of the specific lot. For precise GLUT-inhibitory applications, phlorizin content (which is hydrolysed to phloretin by gut glucosidases) should be included in the total phloretin equivalent calculation.

Phloretin's aqueous solubility is moderate — approximately 0.5 mg/mL at 25°C. Stability in formulations is good at pH 4–7; alkaline conditions accelerate phenolic ring degradation. Compatible with ascorbic acid (vitamin C) for synergistic skin brightening formulas — vitamin C inhibits DOPA oxidase (a second melanin biosynthesis enzyme downstream of tyrosinase), while phloretin inhibits tyrosinase and GLUT glucose supply. Stable in solid dosage forms (capsule, tablet) at ambient temperature under nitrogen packaging.

Phloretin's GLUT inhibitory activity is pharmacologically relevant for patients on SGLT2 inhibitor medications (empagliflozin, dapagliflozin) — both target glucose transporters and theoretical additive glucose-lowering activity may require monitoring in diabetic patients. At typical apple extract supplement doses delivering 5–15 mg phloretin, clinically significant additive hypoglycaemic effects are unlikely but should be noted professionally.

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Frequently Asked Questions — Phloretin

What is the relationship between phloretin and phlorizin?
Phlorizin (phloretin-2′-O-glucoside) is the primary dietary form — found at 0.1–0.5% in apple peel and root bark. Gut brush-border glucosidases cleave the 2′-O-glucose to release phloretin aglycone for absorption. Phlorizin itself also has significant GLUT2 (intestinal brush border) and SGLT2 (renal tubule) inhibitory activity in its intact glucoside form before hydrolysis. The combination of phlorizin's SGLT2 activity and phloretin's GLUT1/2/4 activity after hydrolysis creates a multi-transporter glucose modulating profile from a single apple extract serving.

Is phloretin related to the pharmaceutical SGLT2 inhibitors (gliflozins)?
Yes — pharmacologically related but structurally evolved. Phlorizin was the first identified plant compound to inhibit SGLT2 (renal sodium-glucose cotransporter 2) and reduce renal glucose reabsorption, establishing the pharmacological proof-of-concept for the entire gliflozin drug class (dapagliflozin, empagliflozin, canagliflozin). The pharmaceutical gliflozins are synthetic derivatives of phlorizin's pharmacophore, optimised for SGLT2 selectivity, oral bioavailability, and metabolic stability that phlorizin lacks due to rapid gut hydrolysis and non-selective transporter activity.

Which apple-derived Herbuno products provide phloretin for supplement formulation?
Polyphenols 75% Apple Extract (Malus domestica) is the highest standardised apple polyphenol product available from Herbuno, delivering phloretin alongside phlorizin, chlorogenic acid, and quercetin glycosides. Green Apple Extract Powder provides a whole-apple spectrum with moderate standardisation. Both are appropriate for metabolic syndrome and antioxidant supplement applications; Polyphenols 75% is preferred for precision-dosed formulations where polyphenol content consistency is critical.

Why is phloretin used in topical skin formulations alongside vitamin C?
Phloretin and vitamin C (ascorbic acid) address different steps in the melanin biosynthesis pathway — creating additive skin brightening: phloretin inhibits tyrosinase (the initial L-tyrosine → L-DOPA → dopaquinone conversion) and disrupts melanocyte glucose supply via GLUT inhibition; vitamin C reduces dopaquinone back to DOPA (preventing melanin polymer formation) and also inhibits DOPA oxidase. The two mechanisms are sequential in the melanin pathway — combining phloretin and vitamin C in topical formulations addresses both tyrosinase and post-tyrosinase steps, providing broader and more effective depigmentation than either compound alone. Phloretin additionally enhances vitamin C penetration through the stratum corneum by altering skin permeability.

Related compounds: Isoliquiritigenin, Butein, Naringenin, Glabridin

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Claim-strength scale – High = multiple human RCTs; Moderate = limited trials or strong preclinical convergence; Emerging = early-stage lab or animal data.

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