Antioxidant activities in extracts of five plant sources on stabilization of stripped sunflower oil and egg yolk homogenate

Abstract

out to evaluate the antioxidant potential of five natural sources namely, coconut cake (A), Psidium guajava L. leaf (Guava) (B), Psidium guineense Sw. leaf (Ambul guava) (C), rice bran (D) and sesame cake (E) in both chemical and food model systems (stripped sunflower oil and egg yolk homogenate). Phenolic substances from the test plant materials were extracted using ethanol:water (70:30) solvent system. Total phenolic content (TPC) was determined using Folin-Ciocalteu method and expressed as gallic acid equivalents (GAE) per kilogram of sample. Antioxidant activities of extracts and butylated hydroxytoluene (BHT) were evaluated using deoxyribose degradation assay after adjusting the concentration to 30 μg mL-1. Antioxidant activities of phenolic extracts on stripped (antioxidant free) sunflower oil were determined by comparing the induction time (IT) using the Rancimat Apparatus at 100 0C. Effect of phenolic antioxidants on the inhibition of thiobarbituric acid reactive substances (TBARS) formation was evaluated using egg yolk homogenate as the food model system. Results of TPC as GAE vary in the order, C (195.25±9.56 g/kg) > B (68.83±3.74 g/kg) > D (4.14±0.46 g/kg) > E (2.11±0.29 g/kg) > A (0.77±0.03 g/kg). Phenolic extract of C showed a significantly (p<0.05) higher percentage inhibition of deoxyribose degradation (76.5±1.5 %) than other phenolic extracts and BHT. Inhibition percentages obtained for A, B, D, E and BHT were 39.5±1.4 %, 71.0±2.7 %, 46.1±3.1 %, 42.1±2.5 % and 32.6±2.1 % respectively. Results of IT of stripped sunflower oil and inhibition % of TBARS formation were stated in Table 1.