How to extract flavonoids from onion?

Question

Please include reference(s).

Answer 1

Onion leaves have a higher amount of flavonoids content ( about 2,7 g/kg dry material ) than bulbs.

But the only publications dealing with a method to extract flavonoids from onions refers to bulbs:

Flavonoids are extracted with methanol/water/acetic acid (50:42:8, v:v:v) from fresh bulbs and characterized by HPLC.

http://www.ienica.net/italyseminar/poste...

But there should not be any difference in method to extract bulbs or leaves, because material is similar.