Nobiletin (Polymethoxyflavone · Circadian Rhythm · Neuroprotective)

Compound	Nobiletin (3′,4′,5,6,7,8-Hexamethoxyflavone; Nobiletin)
Chemical class	Polyphenol — Flavone (Polymethoxyflavone; fully methoxylated hexamethoxy Citrus flavone)
CAS	478-01-3
Primary source	Citrus reticulata (mandarin/tangerine peel), Citrus sinensis (sweet orange peel), Citrus nobilis
Key applications	Circadian rhythm modulation; neuroprotective; metabolic syndrome; anti-inflammatory
Claim strength	Moderate
Typical form	Citrus sinensis orange peel extract (co-delivered with tangeretin and sinensetin); aged Chen Pi preparations
Buy from Herbuno	Citrus Sinensis Orange Peel Extract Powder → Organic Orange Peel (Citrus sinensis) Extract Powder →

Name origin: Nobiletin is named after Citrus nobilis (King orange, a mandarin-tangerine hybrid) from which it was first richly isolated. It is the hexamethoxy analogue of tangeretin — fully methoxylated across both A-ring and B-ring positions, with six methoxy groups and no free hydroxyl groups on the flavone scaffold. Traditional use: Nobiletin is a constituent of Chen Pi (aged tangerine/mandarin peel), one of the most important TCM digestive and qi-regulating herbs. Citrus peel preparations in TCM address phlegm, distension, and liver qi stagnation. In Japanese folk medicine, Citrus preparations (particularly Shikuwasa, a small citrus from Okinawa — one of the world's blue zones) have been associated with longevity and metabolic health. Nobiletin is enriched in Okinawan Shikuwasa. Research trajectory: Nobiletin has a uniquely diverse research profile — it is the only dietary compound definitively shown to activate and amplify RORα and RORγ nuclear receptors to reset circadian clock gene expression. This circadian mechanism is mechanistically novel and potentially therapeutic for metabolic syndrome, sleep disorders, and ageing-related circadian disruption. It also crosses the BBB for neuroprotective applications and has strong hepatic lipid-lowering data. Commercial source: Nobiletin is available from Herbuno via Citrus Sinensis Orange Peel Extract Powder and Organic Orange Peel Extract Powder, both standardised Citrus peel preparations delivering nobiletin alongside tangeretin and other PMFs.

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Evidence for Nobiletin Applications

Circadian rhythm modulation: Nobiletin activates RORα and RORγ nuclear receptors — positive regulators of the CLOCK/BMAL1 transcriptional feedback loop that drives mammalian circadian rhythms. In high-fat diet mouse models, nobiletin supplementation (0.1–0.3% diet) restores circadian amplitude and delays metabolic syndrome even in already-obese animals, reducing adiposity, insulin resistance, and dyslipidaemia. This circadian mechanism is pharmacologically unprecedented for a dietary polyphenol and distinguishes nobiletin from other anti-metabolic syndrome compounds. Claim strength: Moderate.

Neuroprotective: Nobiletin crosses the BBB and in Alzheimer's disease models reduces β-amyloid accumulation via MAPK/PKA/CREB pathway activation and BACE1 (β-secretase) inhibition. In vascular dementia and ischaemia models, nobiletin preserves hippocampal neurogenesis and spatial memory. Multiple independent laboratories have replicated these findings. Claim strength: Moderate.

Metabolic syndrome (hepatic lipid and insulin): Nobiletin activates AMP-activated protein kinase (AMPK) in the liver, reducing de novo lipogenesis and improving fatty acid oxidation. In high-fat diet and streptozotocin-induced diabetes rodent models, nobiletin reduces liver steatosis, fasting glucose, and HbA1c-equivalent markers. The mechanism parallels metformin's AMPK-dependent pathway. Claim strength: Moderate.

Anti-inflammatory and cardiovascular: NF-κB and NLRP3 pathway inhibition reduces pro-inflammatory cytokine production in macrophage and vascular endothelial models. Endothelial nitric oxide synthase (eNOS) activation improves endothelial function and reduces atherosclerotic plaque development in ApoE-knockout mouse models. Claim strength: Moderate.

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Dosage & Formulator Specification

No human clinical dosing data exist for isolated nobiletin. Preclinical effective doses of 10–50 mg/kg in rodents correspond to estimated human equivalent doses of 100–500 mg/day (70 kg adult, allometric scaling). Commercial supplementation of orange peel extract at 200–500 mg/day with nobiletin content of 1–3% delivers 2–15 mg pure nobiletin — lower than preclinical effective doses. Higher standardisation extracts (nobiletin ≥10%) are available from specialty Citrus extract suppliers.

For formulator specification: orange peel extract standardised to total PMFs ≥5% (with nobiletin as primary marker) is the most achievable commercial specification. HPLC quantification of nobiletin, tangeretin, and sinensetin as individual PMF markers provides the most complete quality picture. Aged Chen Pi (Xin Hui) extracts may have higher total PMF content than standard orange peel extracts due to the ageing concentration effect.

Nobiletin's logP (~3.2) requires lipid-based or emulsified delivery for good oral bioavailability. Phospholipid complexes, SMEDDS, and nanoemulsions all improve nobiletin absorption significantly versus raw powder. For solid dosage applications, microencapsulation or co-crystallisation with cyclodextrins is practical. Stable under normal manufacturing conditions; light-sensitive in solution.

Nobiletin modulates CYP1A2 and CYP3A4 in vitro — potential pharmacokinetic interactions with drugs metabolised by these enzymes. Clinical significance at typical dietary supplement doses is unconfirmed; note for professional advice in multi-drug patients.

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Frequently Asked Questions — Nobiletin

What is the ROR mechanism and why is it relevant to metabolic health?
RORα and RORγ (RAR-related Orphan Receptors) are nuclear transcription factors that function as positive elements of the mammalian circadian clock — activating CLOCK and BMAL1 expression to drive the 24-hour transcriptional oscillation that governs metabolism, immune function, cell division, and numerous physiological processes. Circadian disruption (shift work, jet lag, ageing) is mechanistically linked to metabolic syndrome, diabetes, and accelerated ageing. Nobiletin's ROR activation restores circadian amplitude, essentially strengthening the biological clock and secondarily improving metabolic parameters.

Is the Okinawan Shikuwasa fruit a reliable source of nobiletin?
Yes — Shikuwasa (Citrus depressa, Hirami lemon, Okinawan flat lemon) contains particularly high nobiletin concentrations in its peel (1.5–5% dry weight PMF total, enriched in nobiletin versus tangeretin). Shikuwasa juice products are commercially available in Japan; Shikuwasa peel extract is used in some Japanese supplement formulations. The fruit's Okinawan blue zone cultural context adds compelling supplemental positioning for longevity-oriented products.

How does nobiletin compare to metformin in metabolic pathway overlap?
Both activate AMPK in the liver, reducing hepatic glucose production and fatty acid synthesis while promoting fatty acid oxidation. Nobiletin additionally activates circadian clock genes (ROR mechanism) which metformin does not. Nobiletin has no established clinical blood-glucose-lowering evidence equivalent to metformin's extensive RCT base. The mechanistic overlap is pharmacologically interesting; nobiletin is a nutritional/functional food ingredient complementary to, not a substitute for, pharmaceutical antidiabetic therapy.

Which Herbuno products provide the best nobiletin concentration?
Citrus Sinensis Orange Peel Extract Powder and Organic Orange Peel Extract Powder both deliver nobiletin as part of the total Citrus PMF spectrum alongside tangeretin, sinensetin, and hesperetin. These are the most accessible standardised sources. For applications requiring higher nobiletin standardisation, specialty Citrus extract suppliers can provide PMF-enriched preparations; contact Herbuno via the quotation page for availability.

Related compounds: Tangeretin, 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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