This study aimed to evaluate the potential of soybean-promoted acidic nitrite reduction and to correlate this activity with the content of phenolics and with the bactericidal activity against Escherichia coli O157:H7. Extracts of embrionary axes and cotyledons enriched in phenolics increased •NO formation at acidic pH at values that were 7.1 and 4.5 times higher, respectively, when compared to the reduction of the nonenriched extracts. Among the various phenolics accumulated in the soybean extracts, five stimulated nitrite reduction in the following decreasing order of potency: epicatechin gallate, chlorogenic acid, caffeic acid, galic acid and p-coumaric acid. Extracts of embrionary axes presented higher contents of epicatechin gallate and caffeic acid, compared to that of cotyledons, indicating a positive correlation between activity of the extracts and content of phenolics with regard to nitrite reducing activity. Soybean extracts enriched in phenolics interacted synergistically with acidified nitrite to prevent E. coli O157:H7 growth. The results suggest that soybean phenolics may interfere with the metabolism of •NO in an acidic environment by accelerating the reduction of nitrite, with a potential antimicrobial effect in the stomach.
Abstract:Although soybean isoflavones naturally accumulate in their conjugated forms, the beneficial effects on human health of soybean-containing foods have been credited to their aglycone forms. In the present study we analyzed the effects of a chemical agent, sodium nitroprusside (SNP), in eliciting the exudation of nonconjugated isoflavones from intact soybean seeds, embrionary axes and cotyledons. The isoflavones in the exudates were determined by high performance liquid chromatography and mass spectrometry. The effect of the exudates on the emission of nitric oxide (NO) and on the proliferation of breast carcinoma cells (MCF-7) was also evaluated. SNP elicitation increased the production of the aglycone forms dose-and time-dependently. Exudates of embrionary axes and cotyledons stimulated NO emission and showed biphasic effects on viability of MCF-7 cells. At lower concentrations both extracts presented proliferative effects (10-25%), and at higher concentrations inhibited (15%) cell proliferation. The biphasic effect might be due to the action of isoflavone aglycones in activating estrogen receptors which in turn stimulate the production of NO. Overall, the results suggest that soybean extracts enriched in isoflavone aglycones by elicitation with SNP could be exploited as a functional ingredient in the food industry.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.