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.
