Cinnamaldehyde and cinnamic acid from cinnamon bark (Cinnamomum verum) increase the binding of glucose to human albumin

AUTORI

ABSTRACT

Traditional herbs and spices are commonly used to control glucose plasma concentration; among these cinnamon (Cinnamomum verum) has been recognized to have the greatest effect. A number of studies have shown that adding cinnamon to diet can help to lower the glucose level. The aim of this study is to identify the cinnamon components that are able to modify the plasma glucose concentration. The cinnamon bark of Cinnamomum verum, analyzed by HPLC, contains cinnamaldehyde, cinnamic acid as well as eugenol. The effect of these components was studied on glucose-albumin binding in human serum albumin (HSA) and human plasma. Glucose-HSA solutions and human plasma containing no or serial concentrations of cinnamon components were prepared, and free glucose in these solutions was measured by the picric acid method. In our study, cinnamaldehyde and cinnamic acid decreased the levels of free glucose in glucose–HSA solution and in human plasma in a dose-dependent manner while eugenol had no effect. The effect of cinnamaldehyde and/or cinnamic acid is related to the presence of native HSA. Thus, when albumin was absent or has been denatured, cinnamaldehyde and/or cinnamic acid did not modify the free glucose levels, suggesting that the native structure of albumin is essential for such activity. The interaction of HSA with cinnamaldehyde was investigated by fluorescence spectroscopy. Cinnamaldehyde increased the intrinsic fluorescence of the protein and the magnitude of fluorescence intensity of glucose–albumin complex. We concluded that cinnamaldehyde produced a rearrangement in the structure of albumin resulting in an increase of the binding of glucose to albumin.

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