The desmutagenic activity of the water extract of Cassia tora L on the mutagenicity induced by 4- nitroquinoline 1-oxide (4-NQO) and N-methyl-N-nitro-N'-nitrosoguani-dine (MNNG) was studied using the SOS Chromotest with Escherichia coli PQ37. The inhibition rates of water extract of Cassia tora L. at concentration of 100 μg/assay were 27.5% and 40% against 4-NQO and MNNG. The water extract of Cassia tora L. was separated into methanol soluble and methanol insoluble parts. The methanol soluble part exhibited higher inhibition effects than the methanol insoluble part against the mutagenic activities of 4-NQO and MNNG. Step-wise fractionation of methanol soluble part was done to obtain methanol, ethyl acetate and water fractions. Among these fractions, water fraction had the strongest inhibitory effects of 23.0 and 19.0% against mutagenicities of MNNG and 4NQO, repectively. The results clearly indicated that the water fraction showed much stronger antimutagenicity against MNNG than 4NQO. The inhibition rates of aqueous fraction of methanol-soluble from water extracted Cassia tora L. at concentrations of 1.0 10, 100 and 250 μg/assay were 8.0%, 12.0%, 25.5% and 43.0%, respectively. The water fraction showed the inhibitory effects with dose response against the mutagenic activities induced by MNNG.

The desmutagenic activity of the water extract of Areca catechu L. on the mutagenicity induced by aflatoxin B1 (AFB1), N-methyl-N-nitro-N'-nitrosoguani-dine (MNNG), mitomycin C (MMC) and 4-nitroquinoline 1-oxide (4-NQO) was studied by using the SOS Chromotest with Escherichia coli PQ37. The inhibition rates of water extract of Areca catechu L. at concentration of 100μg/assay were 41.0%, 47%, 46%, and 32% against AFB1, MNNG, MMC and 4-NQO, respectively. The water extract of Areca catechu L. was separated into methanol soluble and methanol insoluble parts. The methanol insoluble part exhibited higher inhibition effect than the methanol soluble part against the mutagenic activities of MNNG. Step-wise fractionation of methanol insoluble part was done to obtain methanol, ethyl acetate and water fractions. Among these fractions, water fraction had the strongest inhibitory effect of 45.0% against mutagenicities of MNNG. The inhibition rates of aqueous fraction of methanol-insoluble from water extracted Areca catechu L. at concentrations of 1.61, 16.13, 161.29 and 322.58μg/mL were 12.0%, 24.0%, 47.5% and 62.0%, respectively. The water fraction showed the inhibitory effects with dose response against the mutagenic activity induced by MNNG.