Protective effects of four Iranian medicinal plants against free radical-mediated protein oxidation

The role of oxidative protein damages in the pathophysiology of human diseases is currently a topic of considerable interest as oxidised proteins has been implicated in a wide spectrum of clinical disorders. In this study, the antioxidant activities of four Iranian medicinal plants, namely Teucrium polium, Cyperus rotundus, Anethum graveolens and Nasturtium officinale against metal–catalysed protein oxidation were evaluated by pro-oxidant model (Fe2+/ascorbate) in rat liver homogenates. The addition of Fe2+/ascorbate to the liver homogenate significantly increased the extent of protein oxidation, such as protein carbonyl (PCO) formation and loss of protein-bound sulphydryl (P-SH) groups. Furthermore, the rates of reactive oxygen species (ROS) formation and lipid peroxidation (LPO) were also increased. The plant extracts showed inhibitory effects against PCO formation, P-SH oxidation, ROS formation and LPO to varying degrees. Based on this study, the order of antioxidant activity against protein oxidation was found to be: T. polium > C. rotundus > A. graveolens > N. officinale. The protective effects of each plant extract could be due to its polyphenolic content. In that respect, the T. polium extract with highest polyphenolic content has more antioxidant activity against protein oxidation.