Mullen W., Edwards C.A., Crozier A. (2006) Absorption, excretion and metabolite profiling of methyl-, glucuronyl-, glucosyl- and sulpho-conjugates of quercetin in human plasma and urine after ingestion of onions. Br J Nutr 96:107-16 PubMed (16869998)

Compound Mean content
Flavonols, total 275 µmol/270 g
Quercetin 3,4'-O-diglucoside 107 µmol/270 g
Quercetin 4'-O-glucoside 143 µmol/270 g
Isorhamnetin 4'-O-glucoside 11 µmol/270 g