Effect of bitter gourd extracts on the mutagenicity of 1-aminopyrene reacted with nitrite using ames test

Abstract

This study was conducted to investigate the mutagenic activity of raw and cooked bitter gourd (Momordica charantia) including raw fruit extract (RW), blanching water (BW), hot water extract from blanched fruit (HB), stir-fried fruit extract (SF), and stir-fried fruit (pre-squeezed with salt) extract (SS). In addition, the effects of extracts in modifying the mutagenic activity of mutagen freshly prepared by the reaction between 1-aminopyrene and sodium nitrite and the effects when adding each extract at the beginning of the same reaction using Ames test on Salmonella typhimurium strains TA98 and TA100 without enzymatic activation were also determined. The data for mutagenic activity were expressed as a number of histidine revertant colonies/plate and expressed as percentage of modification for mutagenic modification effect. The results showed that all extracts had no direct mutagenic activity either with or without sodium nitrite treatment on both tester strains. The effect of bitter gourd extracts in modifying the mutagenic activity of newly formed mutagen showed that RW had the mutagenic enhancing effect on S. typhimurium strain TA98 (%enhancement = 9.54-147.62). However, there was no mutagenic enhancing effect on S. typhimurium strain TA100 (%enhancement <20%). For cooked bitter gourd extract, it was found that the percentage of mutagenic enhancement of BW (116.12%-338.06% and 74.93%-109.95% for TA98 and TA100, respectively) tended to be higher than that of HB on both stains (42.61%-140.85% and 8.59%-77.29% for TA98 and TA100, respectively). In addition, the similar trend was found from the results of the stir-fried bitter gourd. SS showed lower enhancing effect on the mutagenicity of newly formed mutagen than SF. The results of the effect of bitter gourd extracts added before starting the mutagen forming reaction showed that all extracts exhibited enhancing effects on S. typhimurium strains TA98 and TA100. In addition, the percentage of mutagenic enhancement of BW (74.21%-348.69% and 13.10%-74.97% for TA98 and TA100, respectively) showed a higher trend than that of HB on both strains of S. typhimurium (37.19%-57.46% and 3.54%-34.66% for TA98 and TA100, respectively). SS showed lower values of the percentage of mutagenic enhancement when comparing with SF on S. typhimurium strain TA98. However, when tested with S. typhimurium strain TA100, it was found that the results were different. These values obtained from SS (19.06%-88.48%) tend to be higher than that of SF (2.90%-57.09%). The present study provides the information that raw and cooked bitter gourd are safe for consumption in consideration of mutagenicity. In the case of cooking, the fruit should be pretreatment first. These pretreatment methods such as blanching before boiling or squeezing with salt before stir frying not only reduce the bitter taste of this fruit, but may also reduce the risk of promoting mutagenic effects of some mutagens that may be contaminated in food.