Photophysical behavior of a new cholesterol attached coumarin derivative and fluorescence spectroscopic studies on its interaction with bile salt systems and lipid bilayer membranes

Abstract

A new fluorescent-cholesterol (Cum-Chl) molecule has been synthesized by attaching 3-acetyl-7-(diethylamino)-2H-chromen-2-one (Cum) to cholesterol via cholesterol bound β-keto ester. The β-keto ester was synthesized from the corresponding nitrile by applying the Blaise reaction. The molecule forms H-aggregates in solutions. The efficiency of aggregation is high in water. The H-aggregates are non-fluorescent in non-aqueous solvents but fluorescent in water. Aqueous bile salt media suppress the formation of H-aggregates, this effect being more pronounced for sodium deoxycholate (NaDC) which is more hydrophobic. With increasing bile salt concentration, the enhancement of monomeric fluorescence intensity of Cum-Chl generally follows the progressive miceller aggregation of bile salts. Incorporation of Cum-Chl into the dimyristoylphosphatidylcholine (DMPC) lipid bilayer membrane results in a significant enhancement of monomeric fluorescence intensity. The variation of fluorescence intensity is also sensitive to the thermotropic phase transition of the bilayer. It is seen that in such aqueous micro- and nanoscale organized media like bile salts and lipid bilayer membranes the monomer-to-aggregate fluorescence intensity ratio reflects the state of organization of the medium.

Hydrophilic Silver Nanoparticles Loaded into Niosomes: Physical–Chemical Characterization in View of Biological Applications

“…Fluorescent measurements were performed (λ = 350–425 nm) using a luminescence spectrometer (LS5013, PerkinElmer) in order to obtain fluorescence anisotropy. The florescence anisotropy (r) was determined by using Equation (1) [53,54,55]. A=Ivv−Ivh×GIvv+2Ivh×G where Ivv, Ivh, Ihv , and Ihh are fluorescent intensities, and subscript v (vertical) and h (horizontal) represent the orientation of polarized light.…”

Chitosan Glutamate-Coated Niosomes: A Proposal for Nose-to-Brain Delivery

“…The solution was then filtered through cellulose filter of 450 nm cut off, and its fluorescent measurements were performed (λ = 350–425 nm) using luminescence spectrometer (LS5013, PerkinElmer). The florescence anisotropy ( r ) was determined by using Equation (2) [ 28 , 29 , 30 ]. where , , and are fluorescent intensities, and subscript V (vertical) and H (horizontal) represent the orientation of polarized light.…”

Synthesis and Characterisation of Coumarins from H-Cardanol

“…Prolonged exposure to microwave irradiation (20 min) resulted in charring (entry 9). [23][24][25][26][27] Knoevenagel condensation of 2 with 3d-g provided 3-acylcoumarins 4d-g without any difficulty (Scheme 1 and Table 2). Overall, the conditions as given in entry 7 of Table 1 were taken as the best for use with other substrates.…”

“…Required β-keto esters 3d-g were prepared from corresponding nitriles 5a-d and ethyl bromoacetate by applying the Blaise reaction (Scheme 2, Table 3). [23][24][25][26][27] Knoevenagel condensation of 2 with 3d-g provided 3-acylcoumarins 4d-g without any difficulty (Scheme 1 and Table 2). Similarly the reaction of 2 with the β-keto ester 3h (prepared by the Blaise reaction from 5e) provided the coumarin 4h as a waxy solid.…”