Radical Scavenging Properties of a Cultured and Wild Teleost in Ekiti State, Nigeria

This project compared the radical scavenging activities (RSA) of Oreochromis niloticus harvested from a pond and two reservoirs located in Ekiti state, Nigeria, using different processing techniques. The RSA of the muscles were analyzed using 1,1, diphenyl-1-picrylhydrazyl (DPPH) method. At various concentrations, the RSA of the fresh sample was significantly different (P˃0.05) from the smoked and oven-dried sample, while the smoked sample and oven-dried samples were not significantly different (P˂0.05) from each other. The fresh fish proved to be a strong radical scavenger at all DPPH concentrations. The concentration dependent RSA thus followed the order; fresh sample > Oven-dried sample > Smoked sample. The RSA of the fish from the three locations was in the order of pond > reservoir 2 > reservoir 1. The consumption of tilapia should be encouraged to supplement the intake of cereals, which are the main staple foods of developing countries, as they may have significant positive health benefits by inhibiting lipid peroxidation and scavenging free radicals that lead to various diseases and cell degeneration. Keyword: antioxidant, tilapia, lipid, peroxidation, reservoir, pond INTRODUCTION Radical scavenger or antioxidant is a molecule that inhibits the oxidation of other molecules and thus protects the human body against free radicals which are produced through normal metabolic processes in vivo and as a result of exposure to radiation or environmental pollution (Bhadra, 2004). Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent thus producing free radicals. In turns, these radicals can start a chain of reactions. These highly reactive species cause damage to cellular components including DNA and produce many pathological and degenerative conditions such as ischemia, anaemia, asthma, arthritis, cancer, heart disease, diabetes, inflammation, neuro-degenertion, Parkinson’s diseases, mongolism, ageing process and perhaps dementias (Polterat 1997). Living tissue can protect itself through different endogenous antioxidants flavonoids and flavones, which are widely distributed secondary metabolites with antioxidant and antiradical properties. (Nakayoma and Yamada, 1995). Besides internal defence, the consumption of antioxidants from dietary sources, which is gaining popularity among nutritionists and dieticians, can help in protecting against the oxidative stress, and thus the onset of many degenerative diseases with less potential health hazard compared with synthetic antioxidants. Lipid oxidation and the radical scavenging processes have been well documented (Pokorný, 1987, Frankel, 1991). A schematic illustration of autoxidation and radical scavenging process is illustrated in Fig. 1 (Frankel, 1991). Autoxidation is the direct reaction of molecular oxygen with organic compounds. Autoxidation of lipids proceeds through a free radical chain mechanism involving initiation, propagation and termination steps (Fig. 1). Lipid oxidation in fish is influenced by several catalytic systems for oxygen activation. To overcome the spin restriction between ground state oxygen and lipids, the reaction requires initiation (or initiator: X•) which may be the activation of ground state oxygen (O2) into singlet oxygen (O2), superoxide (O2•), hydroxyl radical (HOO•), or peroxides (LOOH), or transformation of unsaturated lipids into lipid radicals (L•). Under most circumstances, autoxidation starts in the presence of initiators with an extraction of H-atom from a fatty acid to produce the free radical. Subsequently the reaction proceeds through propagation reactions, which produce further free radicals. In the terminating reaction two free radicals combine to produce non-radical products. In biological tissues such as fish muscle, other components such as proteins, amino acids and ascorbate can interact with these free radicals to terminate the reaction. When components other than Radical scavenging properties of a cultured and wild teleost in Ekiti State, Nigeria http://www.ijSciences. com Volume 4 – October 2015 (10) 52 lipids terminate the reaction, they are often referred