Tangeretin (Polymethoxyflavone · Neuroprotective · Antiproliferative)

Compound	Tangeretin (4′,5,6,7,8-Pentamethoxyflavone; Tangeretol)
Chemical class	Polyphenol — Flavone (Polymethoxyflavone; 5-OH free, A-ring 6,7,8-trimethoxy)
CAS	481-53-8
Primary source	Citrus reticulata (tangerine/mandarin peel), Citrus sinensis (sweet orange peel)
Key applications	Neuroprotective; antiproliferative; anti-inflammatory; BBB-penetrating PMF
Claim strength	Moderate
Typical form	Citrus sinensis orange peel extract; mandarin peel extract; tangeretin as co-PMF with nobiletin in Citrus peel
Buy from Herbuno	Citrus Sinensis Orange Peel Extract Powder → Organic Orange Peel (Citrus sinensis) Extract Powder →

Name origin: Tangeretin is named after tangerine — a variety of mandarin (Citrus reticulata) — reflecting its high concentration in tangerine peel relative to other Citrus species. It is a pentamethoxyflavone, but unlike sinensetin (which is fully methoxylated at 3′,4′,5,6,7 positions), tangeretin retains the 4′-methoxy and has a distinct A-ring methoxylation pattern (5 is unmethylated while 6, 7, 8 are methoxy). Traditional use: Citrus peel has deep roots in both TCM (Chen Pi — aged tangerine peel) and Ayurvedic medicine as a digestive stimulant, carminative, and respiratory expectorant. Aged tangerine peel (Chen Pi, particularly Xin Hui Chen Pi — aged ≥3 years in Xinhui, Guangdong) is one of the most prized TCM botanicals, with polymethoxyflavones including tangeretin and nobiletin as key bioactives alongside essential oils and polysaccharides. Research trajectory: Tangeretin is notable among polymethoxyflavones for its documented blood-brain barrier (BBB) penetration — a property shared with nobiletin but distinguished from more polar flavones. This CNS access drives its neuroprotective research profile for Parkinson's and Alzheimer's disease models. It also has one of the most developed antiproliferative evidence bases in the Citrus PMF class. Commercial source: Tangeretin is available from Herbuno via Citrus Sinensis Orange Peel Extract Powder and Organic Orange Peel Extract Powder, both delivering the full Citrus PMF spectrum including tangeretin and nobiletin as co-actives.

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Evidence for Tangeretin Applications

Neuroprotective (BBB-penetrating): Tangeretin crosses the blood-brain barrier efficiently due to its high lipophilicity (logP ~3.5) and multi-methoxy A-ring conformation. In rodent MPTP-induced Parkinson's disease models, tangeretin at 10–40 mg/kg preserves dopaminergic neurons in the substantia nigra, reduces neuroinflammation, and improves motor function. In Alzheimer's models, tangeretin reduces β-amyloid aggregation and tau phosphorylation. These are among the most consistently replicated neuroprotective findings in the Citrus PMF class. Claim strength: Moderate.

Antiproliferative: Tangeretin inhibits proliferation in breast (particularly hormone receptor-positive), colorectal, and lung cancer cell lines at 20–80 μM via G1 arrest (CDK4/6 inhibition), PARP cleavage, and VEGF-mediated angiogenesis suppression. Unlike most flavones, tangeretin has demonstrated in vivo tumour growth inhibition in xenograft models, a more demanding preclinical standard. Claim strength: Moderate.

Anti-inflammatory: NF-κB inhibition, COX-2 and 5-LOX suppression, and NLRP3 inflammasome modulation are documented for tangeretin across macrophage and synovial fibroblast models. Tangeretin's A-ring trimethoxylation pattern may enhance membrane penetration and nuclear transcription factor access compared to less methoxylated flavones. Claim strength: Moderate.

Metabolic (lipid and glucose): Tangeretin activates PPARα and SREBP-1 pathways to reduce hepatic lipid synthesis and improve fatty acid oxidation in high-fat diet models. Adiponectin upregulation and insulin sensitisation via AMPK have been characterised. Effects are comparable to nobiletin. Claim strength: Emerging.

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Dosage & Formulator Specification

No human clinical dosing data exist for isolated tangeretin. In preclinical studies, effective doses of 10–50 mg/kg in rodents translate to estimated human equivalent doses of 100–500 mg/day (70 kg adult), placing typical supplement dosing of orange peel extract in a biologically plausible range. Commercial orange peel extract at 4:1 concentration (200–400 mg/day) delivers tangeretin alongside nobiletin, sinensetin, and other PMFs as a spectrum.

For PMF-standardised formulations, total polymethoxyflavone content (tangeretin + nobiletin as primary markers) is the appropriate specification — typically 2–5% in quality orange peel extracts. HPLC separation of individual PMFs is achievable; combined PMF standardisation is more common and consistent with the synergistic evidence base for the class.

Tangeretin's high lipophilicity (logP ~3.5) requires lipid-based or emulsified formulation for meaningful oral bioavailability. Self-microemulsifying drug delivery systems (SMEDDS) and phospholipid complexes significantly improve absorption. Microencapsulation is appropriate for powder sachet and tablet applications. Stable across a wide pH range and temperature.

Tangeretin inhibits CYP1A2 in vitro — a theoretical interaction with caffeine, clozapine, and other CYP1A2-metabolised drugs at high supplemental doses. Clinically significant interactions at typical orange peel extract doses are not established; professional monitoring is appropriate for patients on narrow therapeutic index CYP1A2 substrates.

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Frequently Asked Questions — Tangeretin

What distinguishes tangeretin from nobiletin in Citrus peel?
Both are Citrus PMFs: nobiletin is a hexamethoxyflavone (6 methoxy groups, including at 3′ and 4′); tangeretin is a pentamethoxyflavone (5 methoxy groups, with 4′-methoxy but 3′-hydroxyl — wait: actually tangeretin has all five A-ring and B-ring positions methoxylated except the 5-position which is free OH). The key structural distinction: nobiletin has a 3′,4′-dimethoxy B-ring while tangeretin has a 4′-methoxy with the 3′ position being a hydroxyl or methoxy (tangeretin: 4′,5,6,7,8-pentamethoxy). Both cross the BBB; nobiletin has stronger circadian rhythm modulation data while tangeretin has stronger antiproliferative evidence.

Why is BBB penetration significant for a dietary flavone?
Most polyphenols — including quercetin, rutin, and hesperidin — penetrate the BBB poorly or not at all due to their polarity and efflux transporter susceptibility. Tangeretin and nobiletin's high lipophilicity and multi-methoxy conformation allow transcellular diffusion across brain endothelial cells and partial resistance to P-glycoprotein efflux, making them among the few dietary polyphenols with confirmed CNS bioavailability. This property is pharmacologically prerequisite for neuroprotective applications.

What is Chen Pi (aged tangerine peel) and does it contain tangeretin?
Chen Pi is aged dried peel of Citrus reticulata — one of the most commercially valuable TCM materials, with price increasing with age. Ageing (Xin Hui Chen Pi at ≥3 years) increases PMF content relative to essential oils and pectin as volatile constituents evaporate. Tangeretin, nobiletin, sinensetin, and other PMFs concentrate during ageing, providing a mechanistic basis for the traditional preference for aged peel over fresh.

Can tangeretin and nobiletin be co-formulated synergistically?
Yes — the co-occurrence of tangeretin and nobiletin in Citrus peel extracts reflects their natural synergistic relationship. Research comparing individual PMFs versus combined preparations generally shows improved efficacy for the combination, possibly due to overlapping but distinct receptor/enzyme targets. Orange peel extract standardised to total PMFs (tangeretin + nobiletin) captures this synergy without requiring individual compound isolation.

Related compounds: Nobiletin, Sinensetin, Diosmetin, Acacetin

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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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