Physicochemical and Computational Study of the Encapsulation of Resv-4'-LA and Resv-4'-DHA Lipophenols by Natural and HP-β-CDs

Abstract

This study investigates the self-assembly and host-guest complexation behaviour of novel resveratrol-based lipophenols (LipoResv)-resveratrol-4'-linoleate (Resv-4'-LA) and resveratrol-4'-docosahexaenoate (Resv-4'-DHA)-with hydroxypropyl-β-cyclodextrins (HP-β-CDs). These amphiphilic molecules display surfactant-like properties, forming micellar aggregates in aqueous media. Fluorescence spectroscopy was used to determine the critical micelle concentration (CMC), revealing that LipoResv exhibit significantly lower CMC values than their free fatty acids, indicating higher hydrophobicity. The formation of inclusion complexes with HP-β-CDs was evaluated based on changes in CMC values and further confirmed by dynamic light scattering (DLS) and molecular modelling analyses. Resv-4'-LA formed 1:1 complexes (Kc = 720 M^-1), while Resv-4'-DHA demonstrated a 1:2 stoichiometry with lower affinity constants (K₁ = 17 M^-1, K₂ = 0.18 M^-1). Environmental parameters (pH, temperature, and ionic strength) significantly modulated CMC and binding constants. Computational docking and molecular dynamics simulations supported the experimental findings by revealing the key structural determinants of the host-guest affinity and micelle stabilization. Ligand efficiency (LE) analysis further aligned with the experimental data, favouring the unmodified fatty acids. These results highlight the versatile encapsulation capacity of HP-β-CDs for bioactive amphiphile molecules and support their potential applications in drug delivery and functional food systems.

Keywords: bioactive compounds; cyclodextrins; fatty acids; lipophenols; micelles; nanoencapsulation.

Figure 1

Structure of resveratrol lipophenols (LipoResv): resveratrol-4′-linoleate (Resv-4′-LA) and resveratrol-4′-docosahexaenoate (Resv-4′-DHA).

Figure 2

Relative fluorescence at 430 nm (excitation 358 nm) according to the concentration of Resv-4′-LA, Resv-4′-DHA, linoleic acid (LA), and docosahexaenoic acid (DHA) in the absence and in the presence of hydroxypropyl-β-cyclodextrins (HP-β-CDs) in 100 mM sodium phosphate buffer (PBS) pH 7.0 and 35 °C. (A) LA, 0.25 mM HP-β-CDs/LA; (B) DHA, 0.25 mM HP-β-CDs/DHA; (C) Resv-4′-LA, 0.25 mM HP-β-CDs/Resv-4′-LA; and (D) Resv-4′-DHA, 0.25 mM HP-β-CDs/Resv-4′-DHA.

Figure 3

Influence of HP-β-CDs concentration in the relative fluorescence for Resv-4′-LA at pH 7.0 and 35 °C: 0 mM HP-β-CDs; 1 mM HP-β-CDs; 2 mM HP-β-CDs; 5 mM HP-β-CDs; and 10 mM HP-β-CDs.

Figure 4

Effect of HP-β-CDs concentration in the critical micellar concentration (CMC) value of LipoResv and its fatty acids at 35 °C and pH 7.0. (A) LA, (B) Resv-4′-LA, (C) DHA, and (D) Resv-4′-DHA.

Figure 4

Effect of HP-β-CDs concentration in the critical micellar concentration (CMC) value of LipoResv and its fatty acids at 35 °C and pH 7.0. (A) LA, (B) Resv-4′-LA, (C) DHA, and (D) Resv-4′-DHA.

Scheme 1

Equations define the complexation process of Resv-4′-DHA with HP-β-CDs, when it’s done in one step (simultaneous) or in two steps (sequential).

Figure 5

Particle size (nm) by dynamic light scattering (DLS): Resv-4′-LA 10 µM (), Resv-4′-LA 50 µM (), Resv-4′-DHA 10 µM (), and Resv-4′-DHA 50 µM () in PBS at 35 °C and pH 7.0.

Figure 6

Particle size (nm) of Resv-4′-LA 50 µM (), Resv-4′-LA 50 µM with 10 mM HP-β-CDs () in PBS, Resv-4′-LA 50 µM (), and Resv-4′-LA 50 µM with 10 mM HP-β-CDs () in MilliQ water at 35 °C and pH 7.0.

Figure 7

Docking poses corresponding to the most favourable host–guest interaction energies for HP-β-CDs inclusion complexes with six guest molecules: resveratrol (purple), diphenylhexatriene (DPHT) (orange), LA (yellow), DHA (blue), Resv-4′-LA (red), and Resv-4′-DHA (green). Cyclodextrins (CDs) are shown as stick-and-surface representations in grey, whereas guest molecules are rendered in coloured-stick format. Two perspectives are shown for each complex: a front view and a lateral view, highlighting both internal accommodation and external extension of the guest structures.

Figure 8

Designed model systems of micellar aggregates for Resv-4′-LA ((left), contains 30 monomeric units) and Resv-4′-DHA ((right), 24 units). The structures correspond to the clusters extracted from the final 100 ns simulation trajectories associated with the most favourable intermolecular interaction energies, as determined by Molecular Mechanics/Generalized Born Surface Area (MM-GBSA) analysis. Micellar models are shown as coloured sticks.