Extraction of phenolic compounds and in vitro antioxidant capacity of prickly pear seeds

The extraction of phenolic compounds from prickly pear seeds was studied. Extraction experiments were carried out by investigating the effect of solvent nature (acetone, ethanol, methanol and water), solvent concentration (25-100%), sample to solvent ratio (0.2/10 to 0.8/10 g/ml), extraction time (30-150 min), and temperature (25-90 degrees C) on the recovery of phenolic compounds and antioxidant activity of the extracts. Total phenolic content was assessed to determine the antioxidant compounds while ferric-reducing power and free radical scavenging activity were used to evaluate the antioxidant activity of prickly pear seed extracts. Experimental results showed that all extraction parameters had significant effects (p < 0.05) on total phenolic content and antioxidant activities of the extracts. The best conditions were: 75% acetone, 0.2 g/10 ml, 90 min, and 90 degrees C with values of 416 mg gallic acid equivalents/100 g for total phenolic content, 237 mg ascorbic acid equivalents/100 g for ferric-reducing power, and 95% for free radical scavenging activity. Ferric-reducing and free radical scavenging potentials were found to be positively significantly correlated with phenolic content under the influence of all extraction parameters.