Kaempferol (Flavonol · Nrf2 Activator · Cardiovascular Antioxidant)
| CAS No. | 520-18-3 |
| Class | Polyphenol · Flavonol · Flavonoid |
| Source | Brassica oleracea (Broccoli, kale); Camellia sinensis (Tea); Ginkgo biloba (Leaves); capers, dill, chives |
| Claim strength | Moderate |
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Name origin: Kaempferol was first isolated from Kaempferia galanga (galangal) in the early 20th century, giving the compound its name. Structural distinction: It differs from quercetin only by the absence of the 3′-hydroxyl on the B-ring — a single change that meaningfully shifts receptor binding profile and metabolic behaviour. Epidemiological prominence: The Women's Health Study documented a 40% lower cardiovascular disease risk in women with highest vs lowest dietary kaempferol intake — one of the strongest flavonol–CVD associations in prospective data. Research trajectory: Increasingly studied for Nrf2 pathway activation and ERβ-selective phytoestrogenic activity, distinguishing it from other common flavonols.
Evidence for Cardiovascular Protection, Nrf2 Activation & Anti-Inflammation
Cardiovascular protection: Multiple prospective cohorts link dietary kaempferol inversely with CVD mortality. Mechanistically: inhibits LDL oxidation, reduces platelet aggregation, improves endothelial function via eNOS activation, and inhibits vascular smooth muscle proliferation. Claim strength: Moderate.
Nrf2 pathway activation: Kaempferol upregulates glutathione synthesis enzymes (GCL, GSS), haem oxygenase-1 (HO-1), and NQO1 — inducing the body's own antioxidant defence rather than acting as a direct radical scavenger. This indirect mechanism is considered more biologically durable than ORAC-type antioxidant effects. Claim strength: Moderate (preclinical strong; human data emerging).
Anti-inflammatory: Inhibits COX-2, iNOS, and NF-κB across multiple cell types; reduces TNF-α, IL-1β, IL-6, and PGE2. Anti-inflammatory potency is comparable to quercetin in most experimental models. Claim strength: Moderate.
Phytoestrogenic (ERβ-selective): Kaempferol binds oestrogen receptor β with moderate affinity. ERβ-selective agonism is generally considered to carry a more favourable safety profile than non-selective phytoestrogenic activity. Relevant to bone density and cardiovascular-protective positioning in postmenopausal formulations. Claim strength: Emerging.
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Dosage & Formulator Notes
Dietary vs supplement intake: Epidemiological evidence relates to dietary kaempferol (2–30 mg/day from flavonoid-rich foods). Supplement doses in emerging research: 20–200 mg/day. No established clinical dose for isolated kaempferol. Most commercial exposure is via standardised ginkgo extract (24%/6%), where kaempferol glucosides form ~one-third of the flavone glycoside fraction.
Formulator specification: For kaempferol as an isolated active, specify source botanical and HPLC purity. For ginkgo-based formulations, the full flavone triad (kaempferol + quercetin + isorhamnetin) is delivered at the standardised ratio.
Synergistic pairs: Quercetin (complementary flavonol antioxidant), sulforaphane (additive Nrf2 activation), isorhamnetin (natural metabolite combination from ginkgo), resveratrol (combined cardiovascular polyphenol stack).
Frequently Asked Questions — Kaempferol
How does kaempferol differ from quercetin?
Kaempferol lacks the 3′-hydroxyl group on the B-ring that quercetin has. This shifts its receptor profile: kaempferol is more ERβ-selective and has distinct Nrf2 activation kinetics. Both are potent antioxidants and anti-inflammatory agents, frequently found together in tea, broccoli, and ginkgo.
What is Nrf2 and why is kaempferol's activation of it significant?
Nrf2 is the master transcription factor for cellular antioxidant defence — its activation upregulates glutathione synthesis enzymes, haem oxygenase-1, and other cytoprotective proteins. Compounds that activate Nrf2 (sulforaphane, kaempferol, carnosol) induce sustained antioxidant enzyme expression rather than providing transient direct radical scavenging, which many researchers consider more biologically impactful.
What are the highest food sources of kaempferol?
Capers are the most concentrated single food source (>300 mg/100 g dry weight). Other significant sources: kale, dill, chives, leeks, broccoli, green tea, elderflower. Steaming or eating raw preserves content better than boiling, which causes significant leaching into cooking water.
Does kaempferol interact with medications?
Kaempferol inhibits CYP3A4 and CYP1A2 at high doses and may affect clearance of co-administered drugs with narrow therapeutic windows. At dietary intake levels, significant interactions are not reported. Standard label precaution for supplements containing kaempferol: consult a healthcare professional before use alongside prescription medications.
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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