A pulse radiolysis study of hyperoside isolated from Hypericum mysorense

Abstract Background The recent growth in knowledge of free radicals in biology is producing a medical revolution that promises a new age in health and disease management. In the last two decades there has been an explosive interest in the role of oxygen free radicals, more generally known as “reactive oxygen species” and of “reactive nitrogen species” in experimental and clinical medicine. Methods The flowering top extract of Hypericum mysorense possessing potent anti-oxidant activity was subjected to bio-active guided isolation. Pulse radiolysis technique was used to determine the transient spectrum and rate constant for the one-electron oxidation of hyperoside by O H , N 3 , NO 2 , NO , CCl 3 OO radicals in aqueous solution. Results Three compounds were isolated and characterized as rutin, quercetin-3- O -galactoside (hyperoside) and quercetin from spectral analysis. The hyperoside radical showed pK a1 and pK a2 at 5.4 and 9.2. Both, Cu(II) and iron(II) ions form chelate with hyperoside. The Cu–hyperoside chelate was able to scavenge O 2 − , k= 7.0(±0.3)×10 6  dm 3  mol −1  s −1 at pH 9. The repair rates for tryptophan and guanosine radicals by hyperoside were also determined. Conclusion The reduction potential of hyperoside radical was determined by cyclic voltammetric and pulse radiolysis methods.