Kazuko Watanabe

Analysis of the antimutagenic effect of cinnamaldehyde on chemically induced mutagenesis in Escherichia coli

SummaryThe antimutagenic effect of cinnamaldehyde on mutagenesis was investigated using ten kinds of chemical mutagen in Escherichia coli WP2s (uvrA−). In addition, the frequency of mutation induction by each mutagen in an SOS repair deficient (umuC−) strain was compared with that in a wild-type (umuC+) strain. Cinnamaldehyde greatly suppressed the umuC-dependent mutagenesis induced by 4-nitroquinoline 1-oxide (4-NQO), furylfuramide or captan. However, cinnamaldehyde was less effective against the umuC-independent mutagenesis by alkylating agents such as N-methyl-N′-nitro-N-nitrosoguanidine and ethylmethanesulfonate. On the other hand, no inhibitory effect of cinnamaldehyde was observed on prophage induction or tif-mediated filamentous growth. These results suggest that a cinnamaldehyde does not prevent the induction of the SOS functions. Despite the decrease in the number of revertants, a remarkable increase was observed in the survival of 4-NQO-treated WP2s cells after exposure to cinnamaldehyde. The reactivation of survival suggests the promotion of some DNA repair system by cinnamaldehyde. This enhancement of survival was also observed in uvrB, polA, recF or umuC mutants and less in lexA or recB, C mutants. However, it was not observed in recA mutants. Therefore, we assume that cinnamaldehyde may enhance an error-free recombinational repair system by acting on recA-enzyme activity.

Detection of mutagenicity of procarbazine by the host-mediated assay with polychlorinated biphenyl (aroclor 1254) as enzyme inducer

Procarbazine [N-isoppropyl-alpha-(2-methylhydrazino)-p-toluamide] was tested for mutagenicity with Salmonella typhimurium G46 in the host-mediated assay by using male BALB/c mice pretreated orally with polychlorinated biphenyl (PCB, Aroclor 1254). Procarbazine was weakly mutagenic without PCB pretreatment, but the pretreatment greatly enhanced the mutagenicity of this compound. The administration of 500 mg PCB/kg 1 day before procarbazine dosage was suitable for the detection of the mutagenicity. Among PCB, 3-methylcholanthrene (3-MC) and phenobarbital sodium (PB), the former 2 inducers showed much stronger enhancing effects than PB. The pretreatment with 3-MC in combination with PB did not cause further enhancement compared with 3-MC alone.