Quercetin is the most abundant flavonol in the human diet (Serban 2016, PMID: 27405810). Mast cell stabilization and NF-κB inhibition are laboratory mechanisms.
They have not been confirmed as clinical anti-inflammatory effects in the pooled human trials cited below, which were null for inflammation overall.
Senolytic activity in humans has been reported only for quercetin combined with the prescription drug dasatinib, not for quercetin taken alone (Hickson 2019, PMID: 31542391).
A lecithin-based Quercetin Phytosome formulation produced plasma quercetin levels the authors described as up to 20 times those from unformulated quercetin, in a single-dose crossover study of 12 healthy volunteers.
All five authors were employed by the company that developed the formulation, so that figure carries a manufacturer conflict of interest and has not been independently replicated (Riva 2019, PMID: 30328058).
Doses used in the trials below range from 500 to 1,000mg/day.