showed the most negative redox potential among all compounds, as shown in Fig. . The addition of a catechol moiety on the B ring from an isoflavone 6 involving three hydroxyl groups on the A ring lowered the redox potential of the compound from 1.202 to 1.018 V (vs. SHE). The orbital lobes localized between C3' and C4' in the HOMO of 7 can rationalize its more elevated HOMO level with the subsequent negative calculated E° value, compared to that of 6, as displayed in Fig. and.