ABSTRACT
Doctorate School of Pharmacological Sciences course in Pharmacology, Toxicology andTherapeutics.
Department ofPharmacology and Anaesthesiology, University of Padova, Largo E. Meneghetti 2, 35131 Padova, Italy
Frees radicals have been implicated in the etiology of several human diseases as well as ageing. The reactive oxygen species (ROS) are harmful byproducts generated during normal cell aerobic respiration implicated in many pathologies including atheromatosis, neurodegeneration and cancer. Therefore, antioxidants are considered important agents in prevention and treatment of various multifactorial diseases. Based on their reaction mechanisms, antioxidant capacity assays can be divided into two major groups: those based on hydrogen transfer (HAT) reactions and others involving single electron transfer (SET) reactions [1].
The aim of this research was to investigate the in vitro antioxidant capacity of plant extracts and isolated natural compounds using several assays based on different mechanisms including Oxygen Radical Absorbance Capacity (ORAC, HAT assay) and DPPH radical scavenging capacity (SET assay). For the extracts we also determined the total soluble phenolic compounds with Folin-Ciocalteu reagent. Oxygen Radical Absorbance Capacity is a method that measures free radical oxidation of a fluorescent probe through the change of its fluorescence intensity. The ORAC assay may quantify the classical ability of an antioxidant to quench radicals by hydrogen donation [2]. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay is one of the most extensively used to evaluate antioxidant activity of plant samples [3]. The chemical reaction mechanism of the DPPH assay is primarily based on SET reactions and hydrogen-atom abstraction is a marginal reaction. The Folin-Ciocalteu assay in which the basic mechanism is a redox reaction, is based on the reduction of phenols by a phosphomolybdic-tungistic acid reagent; total phenolic compounds are estimated by the reduction of the Folin-Ciocalteu phenol reagent [4].
Casimiroaextracts, Croton lechleri sap and isolated phenolic compounds showed antioxidant activity with a different degree of potency also in relation to the antioxidant assay used. The comparative study is a useful tool for the characterization of new natural antioxidants which may be used in oxidative damage prevention.
1) A.R. Ndhlala, M. Moyo, J. Van Staden (2010) - Molecules 15: 6905-6930.
2)G. Cao, R.L. Prior (1999) - Methods Enzymol. 299: 50-62.
3) MS Blois (1958) - Nature 181: 1199-1200
4) O. Folin, V Ciocalteu (1927) – J. Biol. Chem. 73: 627-650.