In iron-fortified
bouillon, reactivity of the iron ion
with (acylated)
flavone glycosides from herbs can affect product color and bioavailability
of iron. This study investigates the influence of 7-O-glycosylation and additional 6″-O-acetylation
or 6″-O-malonylation of flavones on their
interaction with iron. Nine (6″-O-acylated)
flavone 7-O-apiosylglucosides were purified from
celery (Apium graveolens), and their
structures were elucidated by mass spectrometry (MS) and nuclear magnetic
resonance (NMR). In the presence of iron, a bathochromic shift and
darker color were observed for the 7-O-apiosylglucosides
compared to the aglycon of flavones that only possess the 4–5
site. Thus, the ability of iron to coordinate to the flavone 4–5
site is increased by 7-O-glycosylation. For flavones
with an additional 3′–4′ site, less discoloration
was observed for the 7-O-apiosylglucoside compared
to the aglycon. Additional 6″-O-acylation
did not affect the color. These findings indicate that model systems
used to study discoloration in iron-fortified foods should also comprise
(acylated) glycosides of flavonoids.