Bioactive anthraquinones found in plant foods interact with human serum albumin and inhibit the formation of advanced glycation endproducts

The glycation of human serum albumin (HSA) plays a critical role in the development of many disorders. Herein, the anti-glycation effects of several natural dietary anthraquinone derivatives including aloin, aloe-emodin, chrysophanol, emodin, physcion, and rhein were evaluated. The anthraquinones at 100 μM reduced fructose-, methylglyoxal-, and glyoxal-induced HSA glycation by 21% (aloe-emodin) to 92% (aloin), 17% (physcion) to 94% (emodin), and 16% (anthraquinone) to 67% (emodin), respectively. These anthraquinone derivatives also protected HSA by maintaining its free amino acid residues and secondary protein structure as characterized by circular dichroism. The mechanisms of their anti-glycation effects were investigated using rhein as a representative anthraquinone. The interactions between rhein and HSA were evaluated by biophysical characterizations, namely, isothermal titration calorimetry and UV-vis spectroscopy as well as computational modeling. Our findings suggest that the anti-glycation effects of these anthraquinones may be attributed to their binding capacity and stabilization of the HSA protein structure.