EA4021-Pharmacy School

Natural polyphenols (ArOH) have widely been evaluated by these two tests. They may scavenge free radicals following four different mechanisms.

(1) HAT (H Atom Transfer) from the molecule to the radical (direct O-H bond breaking):

ArOH + R^• -> ArO^• + RH

(2) ET-PT (Electron Transfer – Proton Transfer), in which the electron transfer is followed by a proton release:

ArOH + R^• -> ArOH^+• + R^- -> ArO^• + RH

(3) SPLET (Sequential Proton Loss Electron Transfer), in which the proton is first lost:

ArOH -> ArO^- + H⁺; ArO^- + R^• -> ArO^• + R^-; R^- + H⁺ -> RH

(4) Adduct formation, in which the free radical is also scavenged. This may lead to the formation of relatively stable compounds after re-organization and H-transfer from solution.

ArOH + R^• -> [ArOH-R]^• -> stable metabolites