Components and Antioxidant Activity of Phenolic Acids in Red and White Pitaya

The free phenolic acids(FPA),soluble covalent phenolic acids(HPA) and bound phenolic acids(BPA) were extracted and analyzed by high performance liquid chromatography(HPLC),and the antioxidant activities of phenolic acids(PAs),which including 1,1-diphenyl-2-picrylhydrazyl(DPPH) radical scavenging capacity,ferric reducing power and hydroxyl radical inhibiting capacity were determined. The results showed that the contents of PAs showed the following tendency:Red pulp > white pulp > white peel > red peel. The HPA was the main PAs in pulp and the BPA was the main PAs in peel of pitaya. Gallic acid(1700.70 μg/g DW) was the dominated PAs in red pitaya,and protocatechuic acid(1877.50 μg/g DW) was the dominated PAs in white pitaya. The BPA of red peel possessed the highest DPPH radical scavenging capacity(2206.37 mg/L),HPA of white pulp had the strongest reducing ability(A₇₀₀=0.82) and HPA of white peel owned the uppermost hydroxyl radical inhibiting capacity(77.50 U/mL). The correlation analysis of contents and antioxidant activities showed that DPPH scavenging ability and ferric reducing power were significantly(P<0.01) correlated with PAs contents,while hydroxyl radical inhibiting capacity was independent of the PAs contents.