Flavonoids in Microheterogeneous Media, Relationship between Their Relative Location and Their Reactivity towards Singlet Oxygen

Abstract

In this work, the relationship between the molecular structure of three flavonoids (kaempferol, quercetin and morin), their relative location in microheterogeneous media (liposomes and erythrocyte membranes) and their reactivity against singlet oxygen was studied. The changes observed in membrane fluidity induced by the presence of these flavonoids and the influence of their lipophilicity/hydrophilicity on the antioxidant activity in lipid membranes were evaluated by means of fluorescent probes such as Laurdan and diphenylhexatriene (DPH). The small differences observed for the value of generalized polarization of Laurdan (GP) curves in function of the concentration of flavonoids, indicate that these three compounds promote similar alterations in liposomes and erythrocyte membranes. In addition, these compounds do not produce changes in fluorescence anisotropy of DPH, discarding their location in deeper regions of the lipid bilayer. The determined chemical reactivity sequence is similar in all the studied media (kaempferol < quercetin < morin). Morin is approximately 10 times more reactive than quercetin and 20 to 30 times greater than kaempferol, depending on the medium.

Morin Flavonoid Adsorbed on Mesoporous Silica, a Novel Antioxidant Nanomaterial

“…The sum of the physical quenching ( k q ) and chemical reaction ( k R ) constants correspond to the total rate constant ( k T ) [38, 39]. In this work, k T values for the deactivation of singlet oxygen by AMSNPs-MOR dispersed in D 2 O were obtained by measuring the first-order rate of singlet oxygen of luminescence decay in the presence and absence of morin (Eq 11).…”

“…However this value is one order of magnitude lower than that in homogeneous media (1.3 x 10 8 M -1 s -1 in D 2 O pD 7.4) and erythrocyte ghost membranes dispersed in D 2 O pD 7.4 (1.4x10 8 M -1 s -1 )[38]. This could be explained by the interaction between the most acidic hydroxyl moiety of morin (the 2´-OH group on the B ring, pKa 5.2), with the amine group of the NP [53], the formation of dimers and other aggregates of morin on the NP surface, and the slower oxygen diffusion on the solid nanoparticle compared to neat solvents and lipid membranes.…”

“…Some studies have shown that morin is an efficient antioxidant owing to its ability to scavenge free radicals [36, 37] and quench singlet oxygen ( 1 O 2 ) [38–40]. The antioxidant capacity of polyphenols has been determined in different nanoparticles by evaluating the scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical [41, 42].…”

Carminic Acid Linked to Silica Nanoparticles as Pigment/Antioxidant Bifunctional Excipient for Pharmaceutical Emulsions

“…Another explanation could be the quenching effect of the silica matrix [76]; nevertheless, previously we reported that the effect in this nanosystem was not significant [42]. These results display a suitable antioxidant agent, the k T value of this nanomaterial is similar or even greater than the value reported for a few recognized antioxidants such as quercetin or morin [77,78].…”

Theoretical study on the photooxygenation and photorearrangement reactions of 3-hydroxyflavone

“…28 In addition, there has been a particular interest for the photosensitized oxygenation of avonols, as a process contributing to their antioxidant function in living organisms. 29,30 Much information on the mechanism of these photoreactions has been collected via photolysis experiments.…”