Antioxidant activity of Paraguayan plant extracts
Introduction
The role of free-radical reactions in biology has become an area of intense interest. It is generally accepted that free radicals play an important role in the development of tissue damage and pathological events in living organisms [1], [2].
In aerobic life, lipids containing polyunsaturated fatty acids, proteins, nucleic acids and carbohydrates can be oxidised by free radical-mediated reactions [3]. When oxygen is supplied in excess or its reduction is insufficient, reactive oxygen species (ROS) such as superoxide anions, hydroxyl radicals and hydrogen peroxide, are generated [4]. Aerobic organisms are protected against oxygen toxicity by a natural antioxidant defence system involving enzymatic and non-enzymatic mechanisms [5]. If this endogenous system is inadequate for the purpose of scavenging the ROS completely, oxidative damage to important macromolecules occurs.
There is an increasing interest in the natural antioxidants contained in medical and dietary plants, which are candidates for the prevention of oxidative damage.
In the present study, we examine Aristolochia giberti, Cecropia pachystachya, Eugenia uniflora, Piper fulvescens, Schinus weinmannifolia and Schinus terebinthifolia extracts which have long been used in the traditional Paraguayan medicine [6]. The purpose of this study was to determine the free radical scavenging properties and the antioxidant activity of these extracts.
Section snippets
Plant material
The botanical species assayed are detailed in Table 1. Aerial parts from adult specimens were collected in the fall of 2000 at the Botanical Garden from the Botany Department of the National University of Asunción (Paraguay). Specimens of these plants were authenticated by Pharmacist Mirtha Ortiz from the same department.
Extraction
The collected plants, air-dried and powdered, were extracted with MeOH at room temperature. The solvent was evaporated under reduced pressure, giving a residue, which was
Results
All results are reported in Table 3.
Incubation of rat liver microsomes with Fe2+/ascorbate or Cl4C/NADPH at pH 7.4 causes rapid peroxidation, detectable by the thiobarbituric acid method.
When tested in the system dependent on Fe2+/ascorbate, all the extracts showed a dose–response relationship anti-peroxidative activity. E. uniflora and S. terebinthifolia showed the highest inhibitory activity, with IC50 values of 6.9 μg/ml and 7.1 μg/ml, respectively.
Moreover, all the extracts also had an
Discussion
The results of this study on the antioxidant activity of A. giberti, C. pachystachya, E. uniflora, P. fulvescens, S. weinmannifolia and S. terebinthifolia extracts used in the popular Paraguayan medicine clearly show an inhibitory activity on lipid peroxidation. When assayed in the enzymatic system A. giberti, C. pachystachya and S. weinmannifolia were able to inhibit the rat microsomal lipid peroxidation in a lower concentration than that required to inhibit the non-enzymatic lipid
Acknowledgements
This study was supported by grants from the Universidad Nacional de La Plata, Argentina (Programa de Incentivos M096) and the Universidad Nacional de Asunción, Facultad de Ciencias Quı́micas, Dirección de Investigación. This work was carried out as part of the Programa Iberoamericano de Ciencia y Tecnologı́a para el Desarrollo (CYTED, Project IV.11). The authors are grateful to Marı́a C. Abel for the language revision of the manuscript.
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