The synthesis of tetrahydrocurcumin from curcumin

Abstract

Tetrahydrocurcumin (THC) is 1.7-bis(4-hydroxy-3-methoxyphenyl)-heptane-3.5-dione with empirical formula C₂₁H₂₄O₆ and molecular weight 372.4 g/mol, a bioactive beta-diketone compound. It can be isolated from turmeric (Curcuma longa L.) or semi-synthesised from curcumin. Many studies showed that THC could inhibit lipid peroxydation in erythrocyte membranes induced by tert-butylhydroperoxyde, leading to a greater effect than curcumin. It also ameliorated oxydative stress-induced renal injury and mitochondrial dysfunction in brain vasculature during ischemic stroke, as well as exhibited anti-diabetic, Parkinson’s, and anticancer activities. In addition, THC possesses anti-inflammatory, antioxydant, and anti-aging activities. In this report, THC was semi-synthesised from curcumin through two methods. In the first approach, curcumin was acetylated with acetic anhydride in pyridin to afford curcumin acetyl (1) to form THC-acetyl (2) via the catalytic hydrogenation in 10% Pd/C and EtOH at room temperature, followed by deacetylation with NaOH 8% at pH 9 to give THC (3). In another way, catalytic hydrogenation in the presence of 10% Pd/C in solvent or EtOH/NaOH (solid), or EtOH/NH₄OH 25% at room temperature to give THC (3) with in good yields (70-86%). The structures of the compounds were determined by nuclear magnetic resonance (NMR) and liquid chromatography - electrospray ionisation mass spectrometry (LC-ESI MS) spectra.