ELECTRON TRANSFER MECHANISMS IN PHOTOSENSITIZATION BY THE ANTI-INFLAMMATORY DRUG
Douglas E Moore and Jian Wang
Department of Pharmacy, The University of Sydney, Sydney 2006 Australia
The novel anti-inflammatory drug benzydamine has been shown to photosensitize the
reduction of Nitro Blue Tetrazolium, ferricytochrome-c and copper (II)
bathocuproinedisulphonate in aqueous solutions (pH 7.4, 30oC) when irradiated
with UV light at its maximum absorption wavelength of 308 nm. The reduction reactions all
proceed most efficiently when the solutions are deoxygenated, clearly indicating that
direct electron transfer occurs from the excited state of the sensitizer to the substrate.
In aerated solutions the reduction reactions are slower and are partially inhibited by
superoxide dismutase, suggesting that superoxide anion could be involved as an
intermediate when oxygen is present. Benzydamine also photosensitizes the oxidation of
l-histidine and 2,5-dimethylfuran by the singlet oxygen pathway in aerated solutions. The
ability of benzydamine to participate as sensitizer in several types of photochemical
reaction is relevant to the observed clinical photosensitivity of the drug.