Spectroscopic Study On The Interaction Of Three Flavonoids,Lentinus Edodes Polysaccharide And β-casein

Flavonoids are a kind of important natural products with good biological activity,but the poor water solubility and low bioavailability limit its application in food,medicine,cosmetics and other industrial fields.Nano-encapsulation and embedding technology can improve the stability and bioavailability of flavonoids,and have good commercial prospects.Nanocarriers have been a hot research topic in recent years.Protein-polysaccharide natural polymer nanocarriers are widely used in the transportation of biologically active substances due to green safety,wide material sources,good biodegradability and biocompatibility.In this paper,β-casein and Lentinus edodes polysaccharide are used as materials to prepare protein-polysaccharide natural polymer nanocarriers,and the interaction between them with flavonoids（baicalein,luteolin,genistein）were studied,which provided experimental basis for the development of nanocarriers of flavonoids and expanding their applications in the field of functional foods.Ultraviolet-visible absorption spectroscopy,fluorescence spectroscopy,synchronous fluorescence spectroscopy,three-dimensional fluorescence spectroscopy and circular dichroic spectroscopy were used to study the interaction ofβ-casein with three flavonoids（baicalein,luteolin,genistein）and Lentinus edodes polysaccharide.The mechanism of interaction were explored.β-casein andβ-casein-Lentinus edodes polysaccharide nanocarriers were prepared,three flavonoids were encapsulated and the embedding effects were compared.The following conclusions were obtained:1.The three flavonoids（baicalein,luteolin,genistein）could spontaneously form complexes withβ-casein mainly through hydrophobic forces,had a strong binding effect,and quenched the intrinsic fluorescence ofβ-casein.The quenching mechanisms were static quenching.At 298 K,the quenching rate constants were（2.98±0.03）×10¹³L mol^-1s^-1,（7.91±0.15）×10¹²L mol^-1s^-1,（6.15±0.19）×10¹²L mol^-1s^-1,the binding constants were（3.84±0.61）×10⁴L mol^-1,（1.30±0.28）×10⁴L mol^-1,（0.92±0.04）×10⁴L mol^-1,the number of binding sites were 0.9082,0.9334,0.9265,and the binding distances were 3.52 nm,3.36 nm,and 3.95 nm,respectively.The combination of the three flavonoids withβ-casein changed the amino acid microenvironment,induced the conformational changes and changed the secondary structure.2.The interaction between Lentinus edodes polysaccharide andβ-casein formed complex spontaneously and quenched the intrinsic fluorescence ofβ-casein by static quenching mechanism.The main binding forces were hydrogen bonding and van der Waals force,and there was only one binding site between Lentinus edodes polysaccharide andβ-casein.At 298 K,the quenching rate constant was（1.94±0.02）×10¹³L mol^-1s^-1,the binding constant was（3.22±0.17）×10⁵L mol^-1,and the binding distance was 3.95 nm.Lentinus edodes polysaccharide increased the microenvironment polarity of tryptophan residues and changed the conformation ofβ-casein.3.Three flavonoids（scutellarin,luteolin,genistein）could form a complex withβ-casein-Lentinus edodes polysaccharide.At 298 K,the binding constants were（1.75±0.15）×10⁶L mol^-1,（4.09±0.15）×10⁴L mol^-1,（6.09±0.44）×10⁴L mol^-1,the number of binding sites were 1.3430,1.2096,1.1793,and the binding ability and the number of binding sites were higher than that of the three flavonoids withβ-casein alone.The particle size ofβ-casein andβ-casein-Lentinus edodes polysaccharide carriers are mainly about 21 nm,and the encapsulation effects ofβ-casein-Lentinus edodes polysaccharide nanocarrier were better than that ofβ-casein nanocarrier.The above research results prove thatβ-casein andβ-casein-Lentinus edodes polysaccharide nanocarriers can encapsulate three flavonoids（baicalein,luteolin,genistein）.This study provides experimental support for the development of flavonoids nanocarriers,and also provides a basis for the comprehensive utilization of flavonoids.