DPPH assay
This method was developed by Blois (1958) with the
viewpoint to determine the antioxidant activity in a like
manner by using a stable free radical α, α-diphenyl-β-
picrylhydrazyl (DPPH; C18H12N5O6, M=394.33). The
assay is based on the measurement of the scavenging
capacity of antioxidants towards it. The odd electron of
nitrogen atom in DPPH is reduced by receiving a hydrogen
atom from antioxidants to the corresponding hydrazine
(Contreras-Guzman and Srong 1982).
DPPH is characterized as a stable free radical by virtue
of the delocalisation of the spare electron over the molecule
as a whole (Fig. 1), so that the molecules do not dimerise,
like most other free radicals. The delocalisation also gives
rise to the deep violet colour, with an absorption in ethanol
solution at around 520 nm. On mixing DPPH solution with
a substance that can donate a hydrogen atom, it gives rise to
the reduced form with the loss of violet colour. Representing
the DPPH radical by Z• and the donor molecule by AH,
the primary reaction is
DPPH assay
This method was developed by Blois (1958) with the
viewpoint to determine the antioxidant activity in a like
manner by using a stable free radical α, α-diphenyl-β-
picrylhydrazyl (DPPH; C18H12N5O6, M=394.33). The
assay is based on the measurement of the scavenging
capacity of antioxidants towards it. The odd electron of
nitrogen atom in DPPH is reduced by receiving a hydrogen
atom from antioxidants to the corresponding hydrazine
(Contreras-Guzman and Srong 1982).
DPPH is characterized as a stable free radical by virtue
of the delocalisation of the spare electron over the molecule
as a whole (Fig. 1), so that the molecules do not dimerise,
like most other free radicals. The delocalisation also gives
rise to the deep violet colour, with an absorption in ethanol
solution at around 520 nm. On mixing DPPH solution with
a substance that can donate a hydrogen atom, it gives rise to
the reduced form with the loss of violet colour. Representing
the DPPH radical by Z• and the donor molecule by AH,
the primary reaction is
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