Studies on binding mechanism between carotenoids from sea buckthorn and thermally treated alpha-lactalbumin

摘要

Sea buckthorn is a natural food ingredient rich in bioactive compounds such as carotenoids, tocopherols, sterols, flavonoids, lipids, vitamins, tannins and minerals. Herein, fluorescence and UV-vis techniques were used to study the interaction of heat treated alpha-lactalbumin (alpha-LA) with carotenoids from sea buckthorn berries extract (CSB) and beta-carotene. Further atomic level details on the interaction between alpha-LA and beta-carotene were obtained by means of molecular modelling techniques. The quenching rate constants, binding constants, and number of binding sites were calculated in the presence of CSB. The emission spectral studies revealed that, CSB have the ability to bind alpha-LA and form a ground state complex via static quenching process. Maximum degree of quenching was reached at 100 degrees C, where beta-carotene and CSB quenched the Trp fluorescence of alpha-LA by 56% and 47%, respectively. In order to reveal the interaction between CSB and alpha-LA, the thermodynamic parameters were determined from the van't Hoff plot based on the temperature dependence of the binding constant. In agreement with the in silico observations, the thermodynamic parameters enabled us to consider that the association between alpha-LA and beta-carotene is a spontaneous process driven by enthalpy, dominated mainly by the van der Waals interaction, but hydrophobic interactions might also be considered. The interaction between CSB and alpha-LA was further confirmed by UV-vis absorption spectra, where a blue shift of position was noticed at higher temperature suggesting the complex formation. The results provided here supply a better understanding of the binding of CSB to alpha-LA, which can be further exploited in designing new healthy food applications. (C) 2016 Elsevier B.V. All rights reserved.