Effects of lipid chain length on the surface properties of alkylaminomethyl rutin and of its mixture with model lecithin membrane

Three model flavonoid-based bioactive molecules with different lipid chain lengths (RuCn: n = 8, 12, 18) were newly synthesized. The surface properties [surface pressure (π)-area (A), surface potential (ΔV)-surface pressure (π) and dipole moment (u⊥)-surface pressure (π)] of pure RuCn and the lecithin membrane compounds had been investigated by using the Langmuir monolayer technology. The results suggested that the distinctive monolayer behavior of RuCn is strongly dependent on the lipid chain length. The great differences in the monolayer properties brought by the lipid chain length could be attributed to two major factors: (i) the ionization degree of the bulky hydrophilic head group (including hydroxyl and NH groups) alters its local field solely via the surface potential; (ii) tring molecular (or dipole) packing density within monolayers. The excess Gibbs energy (ΔG(ex)) calculated for the RuCn–lecithin mixed monolayers infers that higher stability of the mixed monolayer can be strengthened as the lipid chain length decreases. And the addition of RuCn into lecithin membrane may increase the total u⊥ of the binary mixed monolayers, which could inhibit the hydration of the lecithinʹs hydrophilic head groups. The shorter the lipid chain length of RuCn (e.g., RuC8) is, the higher the surface activity can be. Our findings provide a molecular basis for the application of such class of biomolecules in the functional food, cosmetics and medicine.