Biocatalytic synthesis of palmitoyl vanillylamide in supercritical carbon dioxide through amidation of vanillylamine hydrochloride and palmitic anhydride by lipase

Capsaicin (8-methyl-N-vanillyl-6-nonenamide) is the main pungent component in capsicum fruits. Its analog, palmitoyl vanillylamide, with similar properties, was synthesized through amidation by lipase in supercritical carbon dioxide (SC–CO2) and reaction conditions were optimized. Among five lipases tested, immobilized Mucor miehei lipase, Lipozyme IM, was most effective in synthesizing this analog. The reaction conditions for analog synthesis were optimized and were 50 °C, 17 MPa and pH 8 for 23 h using vanillylamine hydrochloride and palmitic anhydride at a molar ratio of 5/15 as substrates catalyzed by Lipozyem IM at a concentration of 0.5% (w/w). The residual enzyme activity was about 40% and 15% after a 46- and 69-h repeated amidation reaction in a batch reaction under optimized conditions, suggesting further modification of conditions was required.