In vitro Antioxidant Activities of Sodium Zinc and Sodium Iron Chlorophyllins from Pine Needles

Chlorophyll was extracted from pine needles, and then sodium zinc chlorophyllin (SZC) and sodium iron chlorophyllin (SIC) were synthesised by saponification, purification and substitution reaction, using sodium copper chlorophyllin (SCC) as a control. Their crystalline structures were verified by atomic absorbance spectroscopy, UV-VIS spectroscopy and HPLC. Moreover, their antioxidant activities were evaluated and compared with that of ascorbic acid through four biochemical assays: DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity, reducing power, inhibition of beta-carotene bleaching and O-2-scavenging activity. SZC had better antioxidant properties at a lower dosage than SIC and SCC in all assays. In the beta-carotene bleaching assay, EC50 of SZC, SIC and SCC was 0.04, 0.38 and 0.90 mg/mL, respectively, much lower than that of ascorbic acid (4.0 mg/mL). SZC showed a better result (p<0.05) than ascorbic acid in the O-2-scavenging activity assay. The results obtained from reducing power determination were also excellent: the absorbance values were all about 1.0 at 0.5 mg/mL, about half of that of ascorbic acid. In the investigation of DPPH radical scavenging activity, all chlorophyllins had lower activities than ascorbic acid. These results demonstrated the potential bioactivities of chlorophyll derivatives and supported their possible role in human health protection and disease prevention.