Growth-inhibiting effects of Cinnamomum cassia bark-derived materials on human intestinal bacteria

The growth-inhibiting activity of Cinnamomum cassia (Blume) bark-derived materials toward five intestinal bacteria was examined using an impregnated paper disk method and compared with that of tetracycline and chloramphenicol, as well as four commercially available compounds (cinnamyl alcohol, trans-cinnamic acid, eugenol, and salicylaldehyde). The biologically active component of C. cassia bark was characterized as cinnamaldehyde by spectral analysis. The growth responses varied with each bacterial strain tested. In a test using 1 and 0.5 mg/disks, cinnamaldehyde revealed potent inhibition against Clostridium perfringens and Bacteroides fragilis. At land 0.5 mg/disk, growth of Bifidobacterium bifidum was significantly inhibited, whereas weak or no inhibitory activity was obtained against Bifidobacterium longum or Lactobacillus acidophilus. The inhibitory effect was much more pronounced in Cl. perfringens, B. fragilis, and Bi. bifidum, compared to Bi. longum or L. acidophilus. Salicylaldehyde exhibited moderate growth-inhibiting activity, but little or no inhibition was observed from treatments with cinnamyl alcohol, trans-cinnamic acid, and eugenol. In contrast, tetracycline and chloramphenicol significantly inhibited growth of all test bacteria as low as 0.01 mg/disk. These results may be an indication of at least one of the pharmacological actions of C. cassia bark.