EFFECT OF BOVINE SERUM ALBUMIN ON THE LUMINESCENT PROPERTIES OF FLAVONOIDS

Abstract

Flavonoids, as representatives of the class of aromatic phenols, in the structure of which have several cyclic groups and form chelates with many metal ions. Quercetin, morin and rutin belong to the group of polyphenolic compounds that actively absorb ultraviolet light and have wide absorption bands with high values of molar absorption coefficients. Quercetin and morin in ethanolic solutions show their own intense luminescence. The luminescence intensity (Ilum) of rutin, in the 3-oxy group of which the hydrogen atom is replaced by rhamnose, is of little importance.
 In the presence of bovine serum albumin (BSA) Ilum sorbates of morin and rutin complexes increase 2-3 times. This work studied the effect of BSA on Ilum sorbates of flavonoid complexes under the conditions of obtaining the optimal analytical signal.
 BSA has a slight intrinsic luminescence due to the presence of the amino acid tryptophan in its molecule. The possibility of intermolecular energy transfer in the BSA-rutin (morin) system is due to the overlap of the BSA luminescence spectra with the rutin and morin absorption bands. The study of the luminescent properties of BSA in the presence of flavonoids of different concentrations upon excitation of one component - serum albumin, showed that in the spectrum of its luminescence appear new, characteristic of flavonoids bands of sensitized luminescence. As the concentration of flavonoids grows, the Ilum of the acceptor increases with a simultaneous decrease in the luminescence of the BSA donor, which indicates the intermolecular transfer of excitation energy from the BSA donor to the flavonoid acceptor.
 The use of sorbents as a solid matrix causes a significant increase in Ilum complexes Y(III) and Sc(III) with flavonoids (up to 100 times). The highest value of Ilum complex Y(III) with quercetin is found on aluminum phosphate and silica gel 100/160, for complexes Y(III) with rutin on dextran-type sorbent Sephadex G-75 and G-150. Similar results were obtained for the Sc(III) complex with morin.
 It was found that in the presence of albumin in the excitation spectrum of the complex Y(III) – rutin hyper and batochromic shift of the band is observed, which indicates the interaction with BSA with the formation of the complex Y(III) – rutin – BSA. The effect of BSA on the Sc(III) complex with morin has a different character, as the interaction takes place at a low pH value, at which the BSA is not negatively charged and a complex compound with Sc(III) is not formed.
 The introduction of BSA into the system Ln(III) – flavonoid leads to an increase in Ilum. of sorbates of complexes due to intermolecular transfer of excitation energy from BSA energy donor to flavonoid acceptor. The linear region of dependence of luminescence intensity sorbates of complexes on the concentration of morin is observed in the range of concentrations (0.005-0.02)·10-3 mol/l, for rutin (0.005-0.01)·10-3mol/l, for quercetin – (0.005- 0.015)·10-3 mol/l. The range of determined concentrations is sufficient to determine the content and amount of flavonoids in vegetable raw materials.
 Keywords: flavonoids; luminescence; yttrium; scandium; quercetin; morin; rutin; albumin.