Synthesis and antioxidant evaluation for monocarbonyl curcuminoids and their derivatives

Abstract

Introduction: Curcumin is a yellow pigment extracted from the Curcuma longa L, which have a several biological activities and pharmacological properties. Curcuminoids have a wide range as antioxidant not only in a food system, but also for biological systems. Materials and Methods: Acetone, 4-thiomethoxy benzaldehy, pepronal, thiosemicarbazide, 4-phenylthiosemicarbazide and chloroethylacetate. The two Analogous of monocarbonyl curcuminoids (MCCs) have been synthesized by claisen –Schmidt condensation from the reaction between one mole of acetone with two moles of appropriate aromatic aldehydes (4-thiomethoxy benzaldehyde and pepronal) then synthesized their hetero derivatives. The pyrazols derived from the reaction MCCs with hydrazine or one of their derivative (thiosemicarbazide, 4-phenylhydrazine).Results and Discussion:All synthesized compounds were characterized by various spectroscopic techniques such as FTIR, 1HNMR, 13CNMR, Mass spectroscopies and CHN analysis. The antioxidant activity of synthesized MCCs, 1, 2, 1a, 2a, 3, were determined by the ability to scavenge the stable 1,1-diphenyl-2-picryl hydrazyl (DPPH) free radical according to Blois method. The DPPH inhibition activity was measured by spectrophometric method. The polyhydroxy curcuminoid has showed a high activity for scavenging of DPPH radicals, the reason is the hydroxyl phenolic group OH give the compound high activity of scavenging the radical by donating hydrogen atom to the DPPH radicals and inhibition the radical activity by hydrogen atom transfer (HAT). Therefore the scavenge of radical activitywill be in the order: 3>2a>1a>2>1 andthe half maximal inhibitory concentration (IC50) between (17.35-135.2) μmol/L.Conclusions: The proposed struc ture of the synthesized compounds were confirmed by used a spectroscopic technique such as, FTIR, Mass spectra (EI),1H and 13C NMR, The antioxidant activity of curcuminoids were studied by using DPPH as a source of radicals. The higher activity of compounds can be attributed to present the phenolic OH group.