In vitro protective effects of Terminalia arjuna bark extracts against the 4-nitroquinoline-N-oxide genotoxicity

We determined the antimutagenic potential of chloroform, acetone, methanol, methanol+HCl, diethyl ether, and ethyl acetate extracts of Terminalia arjuna bark against the model mutagen 4-nitroquinoline-N-oxide (4-NQO) using the Salmonella/microsome, comet, and micronucleus (MN) tests. Salmonella typhimurium TA100 strain and human peripheral white blood cells were coincubated with various concentrations (from 5 to 500 microg) of the six extracts and 4-NQO (from 0.05 to 2 microg). We found that the 4-NQO mutagenicity was inhibited by more than 70% in the Salmonella/microsome test at the highest nontoxic extract dose of ethyl acetate (50 microg/plate), chloroform (100 microg/plate), acetone, (100 microg/plate), and methanol (500 microg/plate). A less marked antimutagenicity activity (inhibition of about 40-45%) was observed for the acidic methanol and diethyl ether extracts. The comet assay showed that acetone extract (100 microg/mL) was more effective in reducing the DNA damage caused by 4-NQO (ca. 90%), whereas the chloroform, ethyl acetate, and diethyl ether extracts were cytotoxic. In the MN test, the decrease in 4-NQO clastogenicity was observed by testing the mutagen especially with chloroform and ethyl acetate extracts (inhibition about 40-45%). The acetone and methanol extracts showed a less marked activity (33% and 37%, respectively). The results of the present study suggest that T. arjuna bark contains some nonpolar as well as polar compounds with antimutagenic activity against 4-NQO. Several explanations can be suggested, but further investigations are necessary to definitely identify the active compounds.