C-Glucosylation as a tool for the prevention of PAINS-induced membrane dipole potential alterations

Abstract

The concept of Pan-Assay Interference Compounds (PAINS) is regarded as a threat to the recognition of the broad bioactivity of natural products. Based on the established relationship between altered membrane dipole potential and transmembrane protein conformation and function, we investigate here polyphenols' ability to induce changes in cell membrane dipole potential. Ultimately, we are interested in finding a tool to prevent polyphenol PAINS-type behavior and produce compounds less prone to untargeted and promiscuous interactions with the cell membrane. Di-8-ANEPPS fluorescence ratiometric measurements suggest that planar lipophilic polyphenols—phloretin, genistein and resveratrol—act by decreasing membrane dipole potential, especially in cholesterol-rich domains such as lipid rafts, which play a role in important cellular processes. These results provide a mechanism for their labelling as PAINS through their ability to disrupt cell membrane homeostasis. Aiming to explore the role of C-glucosylation in PAINS membrane-interfering behavior, we disclose herein the first synthesis of 4-glucosylresveratrol, starting from 5-hydroxymethylbenzene-1,3-diol, via C-glucosylation, oxidation and Horner-Wadsworth-Emmons olefination, and resynthesize phloretin and genistein C-glucosides. We show that C-glucosylation generates compounds which are no longer able to modify membrane dipole potential. Therefore, it can be devised as a strategy to generate bioactive natural product derivatives that no longer act as membrane dipole potential modifiers. Our results offer a new technology towards rescuing bioactive polyphenols from their PAINS danger label through C–C ligation of sugars.

Membrane Dipole Potential: An Emerging Approach to Explore Membrane Organization and Function

“…The figure shows that the membrane dipole potential exhibited an increasing trend with increasing concentration of cholesterol and exhibited ∼60% increase relative to control POPC membranes (without cholesterol) in the presence of 40 mol % cholesterol . These results are supported by previous observations that suggested cholesterol increases dipole potential in monoolein bilayer and egg PC monolayer and recent observations made with molecular dynamics simulation, , dielectric spectroscopy vibrational spectroscopy, and fluorescence spectrocopy . The ability of cholesterol to increase the dipole potential of membranes could emanate from its unique molecular attributes such as dipole moment perpendicular to the membrane surface or through cholesterol induced changes on membrane organization (e.g., condensation of lipid headgroup area and/or water penetration) .…”

“…44 These results are supported by previous observations that suggested cholesterol increases dipole potential in monoolein bilayer 64 and egg PC monolayer 65 and recent observations made with molecular dynamics simulation, 38,39 dielectric spectroscopy 32 vibrational spectroscopy, 35 and fluorescence spectrocopy. 66 The ability of cholesterol to increase the dipole potential of membranes could emanate from its unique molecular attributes such as dipole moment perpendicular to the membrane surface or through cholesterol induced changes on membrane organization (e.g., condensation of lipid headgroup area and/ or water penetration). 63 In addition, a combination of both these effects could be operative.…”

Polydatin: Pharmacological Mechanisms, Therapeutic Targets, Biological Activities, and Health Benefits

“…The cell-based data of some phytochemicals might be a product of such effects and not caused by specific binding to therapeutic targets. Recent studies have shown that C-glucosylation of polyphenol compounds causes the PAINS effect, while O -glucosylation has no effect on this behavior [ 250 ]. As per previous data [ 250 ], polydatin, an O -glucosylated derivative of resveratrol, is expected to present the same concerns as the aglycone with regards to inducing non-specific reductions in the membrane dipole potential.…”

“…Recent studies have shown that C-glucosylation of polyphenol compounds causes the PAINS effect, while O -glucosylation has no effect on this behavior [ 250 ]. As per previous data [ 250 ], polydatin, an O -glucosylated derivative of resveratrol, is expected to present the same concerns as the aglycone with regards to inducing non-specific reductions in the membrane dipole potential. Therefore, in order to assess if C -glucosylation of resveratrol is able to preserve the promising bioactivities of polydatin described in this review while addressing the mentioned PAINS-related issue, the biological evaluation of this C -glucosyl analog of polydatin is of utmost importance.…”

Marine Compounds, Mitochondria, and Malignancy: A Therapeutic Nexus

“…PAINS-type behavior causes membrane disruption by decreasing the membrane dipole potential, which affects intracellular signaling pathways. The cell-based data of several natural products are likely to indicate such effects which may not be caused by specific binding to therapeutic targets [ 147 ]. This non-specific/specific targeting of mitochondria by marine compounds should be carefully considered in future studies.…”