Potencial antioxidante e citoprotetor da fase vapor do óleo essencial de Cravo da Índia

Abstract

Essential oils (EOs) are sources of potential therapeutic compounds for several diseases. Their antioxidant effects, especially, have been arousing interest of many researchers, since numerous diseases have been related to oxidative stress. Due to the volatile compounds of EOs being directly delivered to lung tissue by inhalation, investigating the effects of their vapor phase becomes revelant. The aim of this study was to evaluate the vapor-phase antioxidante activity of commercial clove EO (Syzygium aromaticum) and its possible cytoprotective effect on lung fibroblasts (MRC-5 strain) subjected to oxidative stress induced by hydrogen peroxide (H2O2). For this purpose, the antioxidante activity of the vapor phase of clove EO was evaluated using the reagents DPPH and ABTS. The results revealed that the clove EO vapor phase was effective in scavenging DPPH and ABTS radicals with IC v50 (%AA) values corresponding to 22.04 μg/mL and 117.5 μg/mL, respectively. The FRAP reduction potential of the EO vapor phase was also assessed and presented R 2 0.746. Furthermore, its cytotoxicity was evaluated by MTT reduction and SRB assays. The vapor phase of clove EO at concentrations from 25 to 200 μg/mL in the 24-hour treatment period was not cytotoxic. For that reason, cytoprotection assays of MRC-5 cells subjected to oxidative stress induced by H 2 O 2 (250 and 500 μM) were performed employing pre- and post-treatments with its vapor phase. Despite the strong antioxidant activity of the clove EO vapor phase, there was no effectiveness in protecting MRC-5 cells from damage caused by oxidative stress. Assays for the detection of reactive oxygen species (ROS) were performed using the compound DCFH-DA. These tests revealed that the vapor phase of clove EO was not able to reduce hydrogen peroxide-induced ROS production and, instead, it generated ROS production per se, showing a synergistic effect in tests with hydrogen peroxide. Therefore, in spite of its strong antioxidant activity, more studies are necessary before the use of clove EO vapor can be suggested for the treatment of respiratory diseases related to oxidative stress.