Inhibition of ⋅OH generation by
desferri-exochelins. Production of ⋅OH was quantitated by
measurements of the hydroxylated salicylate isomers 2,3-DHBA and
2,5-DHBA by GC/MS. A ⋅OH generating system was created by adding
200 μM of salicylic acid to 200 μM xanthine sodium (X), 4.4
milliunits/ml of purified xanthine oxidase (XO), and iron supplied as
1 μM FeNTA. D-EXO is desferri-exochelin 772SM, and Fe-EXO is
iron-saturated exochelin 772SM. Duplicate measurements are shown. When
X, XO, and FeNTA were present, 2,3- and 2,5-DHBA were produced in the
absence of iron chelators or in the presence of Fe-EXO. However, in the
presence of 10 μM deferoxamine mesylate or 4 μM D-EXO, production
of 2,3- and 2,5-DHBA was suppressed (by preplanned ANOVA,
P < 0.01 for 2,3-DHBA and P <
0.001 for 2,5-DHBA). Therefore, both deferoxamine and a
desferri-exochelin prevented generation of ⋅OH by iron chelation
in this cell-free system.