Background: Ascorbic acid is a classic dietary antioxidant which plays an important role
in the body of human beings. It is commonly found in various foods as well as taken as dietary
Objective: The plasma ascorbic acid concentration may range from low, as in chronic or acute
oxidative stress to high if delivered intravenously during cancer treatment. Sheep alpha-2-
macroglobulin (α2M), a human α2M homologue is a large tetrameric glycoprotein of 630 kDa with
antiproteinase activity, found in sheep’s blood.
Methods: In the present study, the interaction of ascorbic acid with alpha-2-macroglobulin was
explored in the presence of visible light by utilizing various spectroscopic techniques and
isothermal titration calorimetry (ITC).
Results: UV-vis and fluorescence spectroscopy suggests the formation of a complex between
ascorbic acid and α2M apparent by increased absorbance and decreased fluorescence. Secondary
structural changes in the α2M were investigated by CD and FT-IR spectroscopy. Our findings
suggest the induction of subtle conformational changes in α2M induced by ascorbic acid.
Thermodynamics signatures of ascorbic acid and α2M interaction indicate that the binding is an
Conclusion: It is possible that ascorbic acid binds and compromises antiproteinase activity of α2M
by inducing changes in the secondary structure of the protein.