Scavenging of peroxynitrite by phycocyanin and phycocyanobilin from spirulina platensis: protection against oxidative damage to DNA

Abstract

Peroxynitrite (ONOO^- is known to inactivate important cellular targets and also mediate oxidative damage in DNA. The present study has demonstrated that phycocyanin, a biliprotein from spirulina platensis and its chromophore, phycocyanobilin (PCB), efficiently scavenge ONOO^-, a potent physiological inorganic toxin. Scavenging of ONOO^- by phycocyanin and PCB was established by studying their interaction with ONOO^- and quantified by using competition kinetics of pyrogallol red bleaching assay. The relative antioxidant ratio and IC₅₀ value clearly indicate that phycocyanin is a more efficient ONOO^- scavenger than PCB. The present study has also shown that PCB significantly inhibits the ONOO^--mediated single-strand breaks in supercoiled plasmid DNA in a dose-dependent manner with an IC₅₀ value of 2.9 ± 0.6 μM. These results suggest that phycocyanin, has the ability to inhibit the ONOO^--mediated deleterious biological effects and hence has the potential to be used as a therapeutic agent.