Evaluation of the antioxidant properties and effects on the biotransformation of commercial herbal preparations using rat liver endoplasmic reticulum

Abstract

The antioxidant herbal ingredients are xenobiotics for animals, many of them must be biotransformed to be eliminated, especially lipophilic compounds. Biotransformation of such xenobiotics- occurs mainly in the hepatic endoplasmic reticulum, a process that may generate ROS and trigger oxidative stress. Therefore, we used rat liver microsomes to test the antioxidant capacity and the effects on biotransformation enzymes of five commercial herbal preparations containing Silybum marianum, Tilia cordata, Crataegus oxyacantha, Avena sativa, Melissa officinalis, Valeriana officinalis; Passiflora incarnata, Foeniculum vulgare, Cassia senna, Peumus boldus and Opuntia ficus-indica, as ingredients -alone or in combination-. With the exception of the aqueous preparation of Opuntia ficus-indica, all the hydro-alcoholic commercial preparations inhibited the oxidation of microsomal lipids and thiols and prevented the oxidative alterations of several microsomal biotransformation enzymes activities, all phenomena induced by Fe3+/ascorbate. They also inhibited the UDP-glucuronyltransferase (UDPGT), GSH-transferase (GST), and N-demethylating, and Monooxygenase cytochrome P450 activities to a lower extent in the absence of oxidative stress. This last phenomenon might be due to the presence of lipophilic substrates in the herbal preparations. Thus, microsomes could be a good biological system to evaluate both the antioxidant properties and the possible interactions of herbal preparations with the enzymes involved in xenobiotics biotransformation.