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

HYPOTHESIS: Caffeoyl 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. EXPERIMENTS: Ring-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. FINDINGS: Derivatization 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.