How is fisetin different from quercetin?

Both are flavonoids, but fisetin's senolytic effect is stronger. A 2018 comparison of 10 flavonoids ranked fisetin highest. Also, quercetin requires dasatinib combination for effect; fisetin shows senolytic effects alone.

Where is fisetin found in food?

Strawberries are richest, with ~160 μg per 100 g. Apples (27 μg), persimmons (11 μg), kiwi (2 μg), onions (5 μg) have smaller amounts. Getting clinical doses from diet is impossible, so supplementation is needed.

Why intermittent dosing?

Senolytics exploit time between senescent cell clearance and reaccumulation. Not daily dosing, but 2 consecutive days every 2 weeks pulse protocol is standard, reducing liver/kidney burden while maintaining effect.

Fisetin: Most Potent Senolytic Among 10 Flavonoids Tested

Fisetin is emerging as a new leader in late-2020s senolytic research. Confirmed as the most potent senolytic among 10 flavonoids in 2018, 220-person human trials are underway.

10-Flavonoid Comparison, Fisetin Ranks First

Mayo Clinic researchers compared 10 flavonoids (quercetin, fisetin, luteolin, apigenin, etc.), finding fisetin showed strongest senolytic activity. Chronic administration to mice late in life improved tissue homeostasis, suppressed age-related pathology, and extended median and maximum lifespan.

Unlike quercetin, fisetin works alone as a senolytic. This makes a major difference in consumer access. Fisetin is available OTC as a supplement.

220-Person Sepsis Trial

The largest ongoing human trial tests elderly sepsis prevention. A Phase 2 randomized double-blind adaptive allocation trial enrolls 220 participants over 65 in:

Fisetin single oral dose 20 mg/kg
Fisetin two oral doses 20 mg/kg (1-day apart)
Placebo

The first large-scale attempt to evaluate whether senolytic therapy prevents clinical deterioration of acute inflammatory disease.

Knee Osteoarthritis Trial

A Phase 1/2 randomized double-blind placebo-controlled trial evaluating fisetin for knee osteoarthritis completed. Since joint senescent cell accumulation is core osteoarthritis pathology, fisetin’s potential for cartilage protection and joint pain reduction is proposed.

Alzheimer’s Risk Single-Arm Trial

A single-arm trial in Alzheimer’s-risk seniors evaluates dasatinib + quercetin + fisetin combination senolytic therapy for safety and preliminary effect.

Fisetin’s Other Actions

Beyond senolytic effects, fisetin has multi-layered biological activities:

Antioxidant: potent free radical scavenging
Anti-inflammatory: NF-κB pathway inhibition
Neuroprotective: BDNF increase, cognitive improvement
Metabolic regulation: insulin sensitivity improvement
Anti-cancer: growth inhibition in cancer cell models

This multiple action positions fisetin as supporting aging’s multiple axes simultaneously.

Dietary Sources

Fisetin-rich foods:

Strawberries: 160 μg per 100 g (top)
Apples (with peel): 27 μg
Persimmons: 11 μg
Kiwi: 2 μg
Onions: 5 μg
Grapes: 4 μg
Cucumbers: 1 μg

Dietary fisetin is ~0.4 mg/day, hundreds of times below clinical doses. Daily strawberries can’t reach senolytic doses.

Intermittent Pulse Protocol

Senolytics’ unique dosing:

Standard protocol: fisetin 100 mg, 2 consecutive days every 2 weeks
Research high-dose: 20 mg/kg (60 kg body weight = 1,200 mg), 2-day dosing
Timing: with fat-containing meal (fat-soluble)

Not daily dosing. Senescent cells take 2-4 weeks to reaccumulate, so intermittent pulses are most efficient.

Safety and Caution

Fisetin’s safety is relatively favorable, but:

High-dose short-term: possible GI symptoms
Anticoagulant combinations: potential interaction
Pregnancy/lactation: limited data, avoid
Dialysis/chronic kidney disease: clinician consultation

2026 Outlook

Fisetin’s position is “research stage but consumer-accessible senolytic”. As ongoing human trials release results in 2026-2027, it’s likely to establish itself as the flagship senolytic supplement.

One of the practical entry ingredients for treating aging as “an intervenable biological process”.

Source: ScienceDirect / ClinicalTrials.gov