Mullen W., Boitier A., Stewart A.J., Crozier A. (2004) Flavonoid metabolites in human plasma and urine after the consumption of red onions: analysis by liquid chromatography with photodiode array and full scan tandem mass spectrometric detection. J Chromatogr A 1058:163-8 PubMed (15595664)

Compound Mean content
Cyanidin 3-O-glucoside 9.3 µmol/270 g
Cyanidin 3-O-(6''-malonyl-glucoside) 48 µmol/270 g
Anthocyanins, total 75 µmol/270 g