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. Author manuscript; available in PMC: 2009 Sep 1.
Published in final edited form as: Biochem Pharmacol. 2008 Jul 2;76(5):589–596. doi: 10.1016/j.bcp.2008.06.012

Figure 6.

Figure 6

Calculation of the rate constant of peroxyl radical reaction with honokiol determined by competition with spin trap EMPO and comparison with vitamin E analog trolox. Insert shows typical ESR spectrum of EMPO/•OR in the presence of 60 mM EMPO and 10 mM AAPH. Accumulation of EMPO/•OR was followed by an increase in intensity of low field component of ESR spectrum indicated by arrow (insert). Ao is ESR amplitude of EMPO/•OR radical adduct in the absence of antioxidants, A is ESR amplitude of EMPO/•OR radical adduct in the presence of antioxidants. The slope of linear regression is equal to the ratio of the rate constants of scavenging reactions of antioxidants to the one of spin trap EMPO. The rate constant of trolox was previously determined as 2.5×106 M−1s−1. Thus, honokiol rate constant with peroxyl radicals is 1.4×106 M−1s−1.