2.6. Antimutagenic activity

The antimutagenic activity of methanol extracts of R. arboreum leaves and flowers was investigated by using the method given by Maron and Ames (1983) with minor changes suggested by Bala and Grover (1989). 4-Nitro-o-phenylenediamine (NPD) and sodium azide were used as direct acting mutagens for TA-98 and TA-100 tester strains of Salmonella typhimurium respectively, whereas, 2-Aminofluorene (2AF) was used as a promutagen for both the strains and S9 rat liver homogenate was used to activate the promutagen by the cytochrome based P450 metabolic activation system (Garner et al., 1972). The 100, 500, 1000, 2500 µg/0.1 ml concentrations of plant extracts were prepared in dimethyl sulfoxide (DMSO) and the analysis was carried out using pre-incubation (PI) and co-incubation (Co-I) modes of experiment so that the bio-antimutagenicity and desmutagenicity could be differentiated. The antimutagenic activity of the extracts was expressed as % decrease of reverse mutations as follows: