Naringenin is a polyphenol of the flavanones class that occurs almost exclusively in citrus plants. It is the aglycone form of naringin, a major bitter component in grapefruit. Naringenin has antioxidant properties but it is especially known for its effect on fat metabolism, particularly normolipidemic and antiatherogenic effects.
There is great interest in using naringenin as a health promoting supplement in staple foods and beverages, as a mean of preventive medicine. A major obstacle challenging the potential use of naringenin as a nutraceutical is its low solubility and the related low oral bioavailability. In order to allow the enrichment of clear beverages with this health promoter, we have used preheated and native β-Lactoglobulin (β-Lg) based nano-vehicles, we previously developed for the delivery and protection of a water soluble polyphenol, EGCG1. β-Lg is the most abundant whey protein and was shown to bind small hydrophobic ligands of diverse structures.
Using UV spectrophotometry and intrinsic fluorescence methods, we have found that naringenin forms complexes with preheated and non-preheated β-Lg, with Ka in the order of 104M-1. No interactions were found using the glycosylated form, naringin, suggesting it does not tend to enter the hydrophobic cavity of β-Lg due to its larger size and higher hydrophilicity. Using 0.54mM β-Lg, we were able to dissolve 1.1mM of the nearly water-insoluble naringenin. Dynamic light scattering experiments revealed that the particles formed are in the 2-8nm range, and therefore colloidal stability and clarity are excellent. We have shown that the naringenin absorbance spectra depends on the polarity of the solvent and that the 322nm peak indicates a hydrophobic microenvironment in the presence of β-Lg. Additionally, a counterintuitive red shift of the intrinsic β-Lg emission spectrum in the presence of naringenin was presented, which may indicate a hydrogen bond formation with the buried Trp19 residue.
Principal Investigator: Prof. Yoav D. Livney livney@technion.ac.il
References
1. Shpigelman, A.; Israeli, G.; Livney, Y. D., 2010, Food Hydrocolloids 24, (8), 735-743.
