Enhanced bioavailability and pharmacokinetics of a novel hybrid-hydrogel formulation of fisetin orally administered in healthy individuals: a randomised double-blinded comparative crossover study

Krishnakumar and colleagues at Akay Natural Ingredients (Cochin, India), in collaboration with Life Extension (Fort Lauderdale, USA), conducted the first published human pharmacokinetic study of oral fisetin. Fifteen healthy adults each received two single doses in a randomised double-blind crossover: 1000 mg of unformulated fisetin (98.2% purity, delivering 982 mg of the compound) on one day, and 1000 mg of a hydrogel-encapsulated formulation called Hybrid-FENUMAT™ (labelled FF-20, containing only 19.2% fisetin, delivering 192 mg of the compound) on another. A 10-day washout separated the two doses. Plasma was sampled over 12 hours after each and analysed by UPLC-MS/MS for fisetin and its methoxylated metabolite geraldol.

The bioavailability enhancement was substantial. Peak plasma fisetin concentration was 238.2 ng/ml after FF-20 versus 9.97 ng/ml after unformulated fisetin — dose-normalised, a 23.9-fold increase in Cmax and a 26.9-fold increase in AUC(0–12 h). Fisetin remained detectable in plasma for 8 hours after the formulated dose but only 2 hours after the unformulated dose. The formulation also reduced conversion of fisetin to geraldol, suggesting protection from first-pass metabolism. No significant adverse events were reported.

The editorial significance is real: this is the peer-reviewed evidence that formulation can meaningfully close the fisetin bioavailability gap, and it is the study the pillar article's "the bioavailability problem" section is anchored on. Unformulated fisetin at 1000 mg produces plasma concentrations 30 to 150-fold below the in vitro senolytic window (1–5 μM). The formulated version gets much closer — 238 ng/ml is approximately 0.83 μM, just below the low end of the senolytic window — but still does not clearly reach the concentration at which fisetin selectively kills senescent cells in the dish.

The critical caveat is the funding structure. Akay Natural Ingredients, which financially supported the study, holds the patents on both FENUMAT™ and Hybrid-FENUMAT™. Four of the six authors are Akay employees. The remaining two are employees of Life Extension, which sells the FF-20 formulation commercially as Bio-Fisetin. This does not invalidate the peer-reviewed PK measurements — the UPLC-MS/MS methodology is standard and the crossover design is appropriate — but it does mean the paper is a manufacturer-sponsored pharmacokinetic comparison of the manufacturer's own product against a generic comparator, without independent replication. Readers should weight the numbers accordingly.