Fisetin

Chemistry and dietary context

Fisetin carries four hydroxyl groups on the flavone backbone, including the 3-hydroxyl that defines the flavonol subclass and the catechol arrangement on the B ring that dominates its redox chemistry. Dietary intake is estimated in the low milligrams per day, orders of magnitude below the amounts used in animal studies, so laboratory findings should not be read as statements about eating fruit.

Senolytic screening work

Other reported activities

• Activation of the Nrf2 antioxidant response and downstream phase II enzymes in cell models.
• Modulation of sirtuin activity and reported effects on NF-kappa B signalling in inflammatory assays.
• Neuroprotective endpoints in cultured neurons and rodent models of cognitive ageing.
• Broad kinase and transcription-factor interactions typical of polyphenols, which complicates target attribution.

Bioavailability and evidence limits

Keep the bottle sealed, dry and out of direct light with the desiccant left in place; fisetin is light-sensitive and its catechol group oxidises on prolonged air exposure, which shows as darkening of the powder. For cell work, weigh capsule contents and prepare a concentrated stock in DMSO rather than in water, protect it from light, aliquot it to avoid repeated freeze–thaw and store aliquots at −20 °C. Dilute into medium immediately before use and check for precipitation, since the compound readily crashes out of aqueous buffers. Include a vehicle-only control, note the lot number, and dispose of unused material through chemical waste.