Caffeoyl maleic fatty alcohol monoesters: Synthesis, characterization and antioxidant assessment

Abstract

HypothesisCaffeoyl malate anhydride, as a good nucleophilic acceptor, can react with lipophilic fatty alcohols to yield interface-confined amphiphiles. The resulting novel molecules are hypothesized to deliver combined functionalities of parent natural building blocks, as emulsifier, stabilizer, ion chelator and free radical scavenger. ExperimentsRing-opening reactions of caffeoyl malate anhydride with fatty alcohols of different chain lengths generated a new group of antioxidant amphiphiles. Structural verification was by MS (mass spectrometry), 1H/13C NMR (nuclear magnetic resonance) and FT-IR (Fourier transform infra-red) spectroscopy. Physicochemical characterization was done by use of DSC (differential scanning calorimetry), FT-IR, determinations of critical micelle concentrations (CMC) and calculations of HLB. Antioxidant activity was assessed by DPPH (2, 2-diphenyl-1-picrylhydrazyl) and hydroxyl radical scavenging activities. Dynamic light scattering (DLS) studies demonstrated surface-activity of G8–G18. Inhibition of iron- and thermally-accelerated lipid oxidation was monitored by thiobarbituric acid reactive substances (TBARS) assay. FindingsDerivatization of caffeoyl malate anhydride with fatty alcohols maintained free radical scavenging activity, and improved hydroxyl radical scavenging activity of caffeic acid. Lipid oxidation at 22 °C was significantly inhibited (up to 3.5 times) in emulsions stabilized by G8–G18 with or without chitosan compared to emulsions stabilized by commercial emulsifiers and stabilizers. Thermal oxidation (at 80 °C) was 10 times less in emulsions facilitated by G8–G18 in combination with chitosan compared to emulsions stabilized by commercial emulsifiers and stabilizers. This study has developed a simple and straightforward approach for developing value-added compounds from underexplored fatty alcohols.