Antimicrobial Properties of Turmeric (Curcuma longa L.) Rhizome-Derived ar-Turmerone and Curcumin

The growth responses of six bacterial strains exposed to materials extracted from turmeric (Curcuma longa) rhizomes were examined using impregnated paper disk agar diffusion. Methanol extracts of turmeric rhizomes exhibited strong inhibitory activity against Clostridium perfringens and weak inhibitory activity toward Escherichia coli at 5 mg/disk. However, in tests conducted with Bifidobacterium adolescentis, B. bifidum, B. longum, and Lactobacillus casei, the methanol extract showed no inhibitory response. The biologically active constituent isolated from the turmeric rhizomes extracts was characterized as ar-turmerone using various spectroscopic analyses including EI-MS and NMR. The responses varied according to the dosage, chemicals, and bacterial strain tested. At 2 and 1 mg/disk, ar-turmerone strongly inhibited the growth of C. perfringens and moderately inhibited the growth of E. coli without any adverse effects on the growth of four lactic acid-bacteria. Of the commercially available compounds originating from turmeric rhizomes, curcumin exhibited strong and moderate growth inhibition against C. perfringens at 2 and 1 mg/disk, respectively, and weak growth inhibition against E. coli at 1 mg/disk. However, little or no activity was observed for borneol, 1,8-cineole, and sabinene against all six bacteria strains tested. The observed inhibitory activity of the turmeric rhizome-derived curcumin and ar-turmerone against C. perfringens and E. coli demonstrate one of the important pharmacological activities of turmeric rhizomes.