Acetylation of curcumin from turmeric rhizome (Curcuma longa) with Ni/SiO2 and pyridine catalysts and its antibacterial activity

Abstract

Turmeric (Curcuma longa) has been known for its antibacterial activity because it contains active curcumin. Antibacterial activity can be amplified by reducing its polarity, one of the ways is by modifying -OH on the phenolic group of curcumin to an acetoxy group by acetylation. The curcuminoid compound was extracted and curcumin was separated by column chromatography. Curcumin was modified by acetylation with Ni/SiO2 and pyridine catalyst. The products were then separated by column chromatography and all compounds were characterized using thin layer chromatography, FTIR, and UV-Vis. All compounds were tested for Escherichia coli and Bacillus subtilis bacteria. The results showed that acetylation curcumin with pyridine was more effective at 94 % conversion of di-O-acetylcurcumin compared to acetylation with Ni/SiO2 catalyst which has 90 % conversion but still in a mixture of di-O-acetylcurcumin, mono-O-acetylcumin and curcumin residual. Di-O-acetylcurcumin showed the highest antibacterial activity against E. coli with inhibitory zone diameters at 2 mm while the mono-O-acethylcurcumin showed the highest antibacterial activity against B. subtilis with inhibitory zone diameters at 3 mm.