Why do the FC, DPPH, TEAC, and FRAP Methods give Different Sesults?

Pavel Stratil, Lea Lojkova*, Helena Pluhackova and Borivoj Klejdus

Reactivity of non-hydroxy- and hydroxy-derivatives of benzoic acid, benzaldehyde and cinnamic acid was investigated by FC, DPH, FRAP and TEAC methods. The non-hydroxyderivatives were non-reactive with the methods. The reactivity of analysed compounds (expressed by micromolar absorption coefficient) determined by the FC method depends on the type of phenolic compound, the number of bound hydroxyl groups, their positions on the benzene ring, and eventual presence of other substituents. The values were generally low. FRAP: only monohydroxy derivatives of cinnamic acid and other benzene derivatives having an additional one or two methoxy groups and o,m- or p,m- dihydroxy derivatives reacted. DPPH: from monohydroxy derivatives, only cinnamic acid derivatives having a methoxy group and benzene derivatives having two methoxy groups reacted. Dihydroxy derivatives reacted similarly as found for the FRAP method. TEAC: all analysed compounds containing hydroxyl groups reacted with various intensities. The method gave higher values than other methods used. Derivatives with substituents in o,p- or m,m- position (with the same electron density) were more reactive. Derivatives with three and four hydroxyl groups: higher reactivity had those with hydroxyl groups in o,m- or p,m- positions and greater molecule symmetry. TEAC method provides the best information about the antioxidant activity of the examined phenolic compounds.

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Published on: Aug 21, 2026 Pages: 21-32

Full Text PDF Full Text HTML DOI: 10.17352/ojc.000048
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