Investigation of the membrane localization and distribution of flavonoids by high-resolution magic angle spinning NMR spectroscopy

Abstract

To investigate the structural basis for the antioxidative effects of plant flavonoids on the lipid molecules of cellular membranes, we have studied the location and distribution of five different flavonoid molecules (flavone, chrysin, luteolin, myricetin, and luteolin-7-glucoside) with varying polarity in monounsaturated model membranes. The investigated molecules differed in the number of hydroxyl groups attached to the polyphenolic benzo-gamma-pyrone compounds. To investigate the relation between hydrophobicity and membrane localization/orientation, we have applied (1)H magic angle spinning NMR techniques measuring ring current induced chemical shift changes, nuclear Overhauser enhancement cross-relaxation rates, and lateral diffusion coefficients. All investigated flavonoids show a broad distribution along the membrane normal with a maximum in the lipid/water interface. With increasing number of hydroxyl groups, the maximum of this distribution is biased towards the lipid headgroups. These results are confirmed by pulsed field gradient NMR measurements of the lateral diffusion coefficients of phospholipids and flavonoids, respectively. From the localization of different flavonoid protons in the membrane, a model for the orientation of the molecules in a lipid bilayer can be deduced. This orientation depends on the position of the polar center of the flavonoid molecule.

Genistein derivatives decrease liposome membrane integrity — Calcein release and molecular modeling study

“…Intrinsic fluorescence properties of fisetin were used by Sengupta et al [7] to show that this molecule was localized and rigidly bound at the polar/apolar interfacial region of lipid bilayer. In a series of 1 H magic angel spinning NMR experiments it was shown that in fact flavonoid molecules are broadly distributed along the membrane normal with a maximal probability of localization close to polar/apolar interface [8]. After intercalation of flavonoids into membrane the antioxidant effects can be achieved by the two complementary mechanisms -i) direct scavenging of ROS by flavonoid molecules and/or ii) reduction of the ROS access to the interior of membrane caused by flavonoidinduced alteration of membrane fluidity.…”

Perturbation of the lipid phase of a membrane is not involved in the modulation of MRP1 transport activity by flavonoids

“…A similar localization was reported for genistein in DMPC membranes [70]. Additionally, it was shown that the spatial orientation in the bilayer depended on the position of the polar centre of the flavonoid molecule [69]. According to the model of Scheidt et al [69], we postulate that the flavonols morin and myricetin were located with their B rings pointing towards the aqueous phase, while their A rings were inserted deeper into the acyl chain region of the membrane.…”

“…Additionally, it was shown that the spatial orientation in the bilayer depended on the position of the polar centre of the flavonoid molecule [69]. According to the model of Scheidt et al [69], we postulate that the flavonols morin and myricetin were located with their B rings pointing towards the aqueous phase, while their A rings were inserted deeper into the acyl chain region of the membrane. On the other hand, apigenin and acacetin were more likely to be oriented with their B rings heading for membrane centre and A rings located closer the surface of the lipid bilayer.…”

“…However, the detailed description of the mechanism in which flavones influence fluorescence of carbocyanine dye in lipid bilayers requires further studies, especially fluorescence lifetimes measurements. Using NMR spectroscopy, Scheidt et al [69] showed that the spatial distribution of flavonoids inside phosphatidylcholine membranes could be quite broad. In the presence of flavonoids, the signals of almost all the protons of the lipid molecule were changed.…”

In vitro effects of prolonged exposure to quercetin and epigallocatechin gallate of the peripheral blood mononuclear cell membrane

“…Most flavonoids, mainly due to their lipophilicity, have the tendency to accumulate in biological membranes, particularly in lipid rafts, where they can interact with different receptors and signal transducers and influence their function through the modulation of the lipid-phase behavior [54]. In vitro studies demonstrated that compounds differing in the number of hydroxyl groups showed a broad distribution along the membrane [55].…”