Oxidation mechanism of bioactive compounds in respect to their chemical structure
Oxidation of FLAVONOLS vs. FLAVANONES
Electrochemistry of pharmacologically important bioflavonoids, which are present in nature
in products as fruits, vegetables, wine, tea is one of the research studies. These compounds exhibit a fundamental
importance because of their antioxidative, anti-hepatotoxic, anti-allergic, anti-proliferative,
anti-osteoporotic, anti-inflammatory properties. They are widely used in pharmacy, cosmetics and
food processing industry. Since they are intensively coloured, they were applied in
historical dyes used for colouring of ancient tapestries since 15 century.
However, they show high instability in the presence of atmospheric oxygen. The mechanism
of degradation of colorants used in old textiles, the stability of intermediates and
decomposition
products is one of our main topics. The degradation products formed during the ageing
process
can be used as fingerprints for the determination of the original materials used as colorants
of artwork.
The strong effect of atmospheric oxygen on the distribution of the oxidation
products of the antioxidants quercetin and luteolin was monitored by HPLC–ESI-MS/MS and HPLC–DAD
analysis. The amounts of oxidative reaction products increase with
exposure time to oxygen. The strong dependence of the formation of oxidation products in the presence of air can
reflect the pharmacological efficiency of these antioxidants
and also explains the controversial
reported values of their dissociation constants.
Oxidation mechanism differs for flavonols comparing with flavones and flavanones. The role of the presence of
C3-OH hydroxyl group and a double bond between atoms C2 and C3 significantly influences the oxidation mechanism.
publications 2009-2019
The influence of the molecular cavity protection on degradation processes of flavonoids was
studied. We proved a protective formation of inclusion complex of quercetin with
b-cyclodextrin.
It was shown that decomposition products formed by the oxidation of quercetin
are stabilized in the cavity of b-cyclodextrin.
In the contrary, molecule of luteolin encapsulated in the cavity of b-cyclodextrin is oxidised
at part, which is not hidden in the cavity. In long time scale, the molecule of b-cyclodextrin
does not protect luteolin against the oxidation by air oxygen. Nevertheless, the oxidation of
luteolin complexed with b-cyclodextrin is more difficult than the oxidation of its free molecule.
publications 2009-2019
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