Inhibitory effects on human neutrophil bursts of raw, grilled and boiled eggplant (<i>Solanum melongena</i> L.)

Abstract

AIM: This study investigated the effects on human cells of grilled, boiled and raw eggplant aqueous extracts on the release of reactive oxygen and nitrogen species (ROS and RNS) during respiratory bursts of human polymorphonuclear neutrophils (PMNs). METHODS: Luminol-amplified chemiluminescence (LACL) was used used to assess the concentrations (ranging from 160 μg/ml to 0.62 μg/ml) at which there was residual biological activity. The respiratory bursts were analysed in two different experiments. The first evaluated the action of the extracts on the cell release of ROS (mainly superoxide and hydroxyl radicals); in the second, L-Arginine (L-Arg) was added to the medium as a nitric oxide (NO) donor before the challenge in order to study the possible quenching reaction of the extracts on the generation of NO and peroxynitrite as by-products of the rapid interaction between O2¯• and NO. RESULTS: Comparison of the antioxidant effects showed that the behaviour of the three extracts was significantly different. Both of the both cooked samples had greater antioxidant effects than the raw sample in both experiments, and these effects were 10-12% greater after the addition of L-Arg. CONCLUSIONS: These findings are in line with those indicating that cooking eggplant increases the principal phenolic compounds (such as chlorogenic and caffeic acids), which are known to have antioxidant activity. This effect is interesting for the strategy of improving the antioxidant charge and restoring redox balance in human cells when the stress generated favours free radicals as a result of a decrease in antioxidant levels.