Palmitoylethanolamide as a novel green gelator in oleogels

Palmitoylethanolamide (PMEA), an endogenous lipid with therapeutic properties, was investigated as a green gelator for cosmetic oleogels. It formed stable gels in olive oil (OO), caprylic capric triglyceride (MCT), octyldodecanol (OD), dicaprylyl carbonate (DC), liquid paraffin (LP) and squalane (SQ) with critical gelation concentrations ranging from 1.0 to 3.2 wt%. Gel strength and oil-binding capacity were superior in high-polar oils such as OO and MCT, whereas long-term stability was better for the non-polar oils such as LP and SQ. C-T phase diagrams revealed larger gel-phase regions in low-polar oils, inversely related to PMEA solubility. Microstructural analyses showed dense networks of needlelike PMEA crystals in all oleogels. X-ray diffraction further confirmed the presence of crystals in all oleogels and revealed that the crystal type in P-OD differs from that in other PMEA-based oleogels. Differential scanning calorimetry indicated that P-OD is less thermal stable than the rest. FTIR confirmed the presence of intermolecular hydrogen bonding within the PMEA-based oleogels. These findings establish PMEA as an efficient, biocompatible gelator for tailoring oleogel properties in cosmetic applications. GRAPHICAL ABSTRACT