12th International Symposium on Bioluminescence & Chemiluminescence

Symposium abstracts:

The role of ortho- and para-semiquinones in the chemiluminescence and antioxidative activity of humus substances

Polewski, Krzysztof¹, Slawinska Danuta¹ , Slawinski Janusz²
1. Dept of Physics, August Cieszkowski Agricultural University, Poznan, Wojska Polskiego 38/42 60637 Poznan, Poland
Email: polewski@owl.au.poznan.pl
2. Dept. of Radio-and Photochemistry, Technical University Poznan, Piotrowo 3, 60-965 Poznan, Poland

Humus substances (HS) are extremely complex, dark and paramagnetic biopolymers which play important role in soil and aquatic environments. The presence in HS polyphenolic (PPh) and quinoid (Q) arrangements (semiquinone, SQ. -stable free radicals) conjugated to aromatic and aliphatic backbone determines redox and optical properties of these biopolymers. The ratio of orto- to para-quinones may affect antioxidative activity (AOA) and reactivity of HS towards reactive oxygen species (ROS). In order to verify this hypothesis the effect of selected PPh and corresponding Q on the electrochemiluminescence (ECL) was studied. ECL arising from the Kolbe reaction was used to evaluate AOA and sensitizing activity of PPh and Q in a single multiparametric measurement. Moreover, chemiluminescence (CL), EPR and optical absorption spectra were measured. The electron density distribution in PPh and Q was calculated using a semiempirical PM3 method. The data indicate that the C-C bond in diketo moieties of o-Q is the weakest one and undergoes splitting to ketocarboxylic acids. Para-PPh exhibit the highest AOA and are the most stable.

This is a preprint of an article accepted for publication in Luminescence: Copyright 2001 John
Wiley & Sons, Ltd (Wiley website)