Fig. 6: pKa profile of luteolin and the radicals generated.
From: Oxygen mediated oxidative couplings of flavones in alkaline water
A The distribution curve of luteolin species in aqueous solution LuH4: luteolin, LuH3−: monoanion, LuH22−: dianion, LuH3−: trianion, and Lu4−: tetraanion. B Experimental (black) and simulated (red) EPR spectrum of LuH•2−. C Spin-density distribution in LuH•2− predicted with DFT (UM062X/6-311+G(d,p)). D Experimental EPR spectrum of LuOH•2− in air-saturated H2O (Black), in H2O with 30% 17O2-enriched molecular oxygen (red) and in 30% 17O enriched water (blue). E Proposed mechanism for the formation of LuOH•2−.
