Flavonoids, a class of polyphenolic substances widely
present in
the plant realm, are considered as ideal hypochlorite scavengers.
However, to our knowledge, little study has focused on the structure–activity
relationship between flavonoids and hypochlorite scavenging capacity.
Herein, we report for the first time the three-dimensional quantitative
structure and activity relationship (3D-QSAR) combined with comparative
molecular field analysis (CoMFA) and comparative molecular similarity
indices analysis (CoMSIA). Four models derived from CoMFA and CoMSIA
with different combinations of descriptors were built and compared;
the CoMFA model, which included both steric and electrostatic fields,
showed great potential (R
2 = 0.989; Q
2 = 0.818) in predictive quality according to
both internal and external validation criteria. Additionally, the
average local ionization energy (ALIE), electrostatic potential (ESP),
and orbital weighted dual descriptor (OWDD) were determined to identify
the key structural moiety for scavenging capacity of flavonoids against
hypochlorite. The computational results indicated that hypochlorous
acid (HClO) serves as an electrophile undergoing electrophilic addition
to the C6 carbon, which has the highest negative charge density, which
are influenced by the functional groups on the flavones. The DFT calculated
mechanism revealed the catalytic role of water of mono- and di-chlorination
reactions, characterized by low activation barriers, and the involvement
of neutral, instead of high-energy carbocation, intermediates.