Suppression of SOS-Inducing Activity of Chemical Mutagens by Cinnamic Acid Derivatives from Scrophulia ningpoensis in the Salmonella typhimurium TA1535/pSK1002 umu Test

A methanol extract from Scrophulia ningpoensis showed suppressive effect of the SOS-inducing activity of the mutagen 2-(2-furyl)-3-(5-nitro-2-furyl)acrylamide (furylfuramide) in the Salmonella typhimurium TA1535/pSK1002 umu test. The methanol extract was re-extracted with hexane, dichloromethane, butanol, and water. An acidic fraction of the dichloromethane fraction showed a suppressive effect. Suppressive compounds in the acidic fraction were isolated by SiO2 column chromatography and identified as trans-cinnamic acid (1), p-methoxycinnamic acid (2), 3,4dimethoxycinnamic acid (3), and 4-hydroxy-3-methoxycinnamic acid (4) by GC, GC/MS, and 1H NMR spectroscopy. Compounds 1-4 suppressed the SOS-inducing activity of furylfuramide in the umu test. Compounds 1-4 suppressed 44, 31, 37, and 36% of the SOS-inducing activity at a concentration of 1.4 μmol/mL. These compounds were assayed with other mutagens, 4-nitroquinoline 1-oxide (4NQO) and N-methyl-N′-nitro-N-nitrosoguanidine (MNNG). In addition, compounds 1-4 were assayed with 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and aflatoxin B1 (AfB1), which requires liver metabolizing enzymes. These compounds showed suppresssive effects of SOS-inducing activity against all mutagens. Methyl esters of compounds 1-4 also showed a suppressive effect of the SOS-inducing activity against furylfuramide and Trp-P-1.