Stigmasterol–Acylglycerol Conjugates: Chemoenzymatic Synthesis as a Shorter Alternative to Chemical Routes and the Impact of Fatty Acid Chain Length on the Physicochemical Parameters of Liposomes

In this study, a two-step chemoenzymatic route was developed for the synthesis of symmetrical acylglycerol–stigmasterol conjugates bearing a stigmasterol moiety at the sn-2 position and saturated acyl chains (decanoyl, C10, or stearoyl, C18) at the sn-1,3 positions. The use of Candida antarctica lipase B (CALB) under mild conditions (0–5 °C) ensured high regioselectivity, successfully preventing acyl migration and eliminating the need for complex protection/deprotection steps. The impact of the synthesized conjugates on DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) model lipid membranes was evaluated using dynamic light scattering (DLS), differential scanning calorimetry (DSC), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and fluorescence spectroscopy. Incorporation of the conjugates broadened the main phase transition of DPPC, reduced membrane fluidity in the liquid-crystalline phase, and limited interfacial hydration in a concentration- and chain-length-dependent manner. The short-chain derivative (C10) maintained smaller, homogeneous liposomes and disrupted lipid packing in the gel phase, whereas the longer-chain derivative (C18) promoted stronger hydrophobic interactions within the bilayer core. These findings highlight the potential of chemoenzymatically derived lipid–phytosterol conjugates for the precise tailoring of nanocarriers in functional food and nutraceutical delivery systems.