Morin, rutin and chrysin (Fig 1.) belong to the group of flavonoids, a very important class of phenolic compounds occurring in all parts of plants. Flavonoids has received increased attention during the last years because of their wide range of biological activities. Beneficial effects of flavonoids have been described for diabetes mellitus, cancer, allergy, viral infections, and inflammations. They can bind to biomolecules, such as hormone carriers and DNA, enzymes. Hydroxyflavones catalyze electron transport and scavenge free radicals [1-3].

Fig.1. Structural formula of chrysin, morin and rutin

Proton-transfer reactions constitute an important class of chemical reactions and have been studied extensively over a long period of time. Many biological systems use proton transfer reactions to communicate between the extra cellular and intra-cellular media, and the rate if these reactions depend on the degree of dissociation of the species in the solution phase. On the other hand, PdCl₂ is widely used as a color forming reagent in spectrophotometric determinations of many drugs [4].

In this study, the stoichiometric protonation constants of chrysin, morin and rutin and the stability constants of Pd(II) complexes of those flavonoids, have been determined in 50% (v/v) water-MDM (methanol:1,4-dioxane:acetonitryle) mixed solvents using a potentiometric method at 25.0 (±0.1)⁰C and the ionic strength 0.2. The protonation constants and stability constants were analyzed by Hyperquad2008 computer program.

References:

1. Van Acker S.A.B.E, Bast A, Van der Vijgh W.J.F. (1998). Structural aspects of antioxidant activity of flavonoids. In: Rice-Evans CA, Packer L, eds. Flavonoids in health and diseases. New York: Marcel Dekker Inc.; pp.221-51.
2. Cody V, Middleton E, Harborne JB. (1986). Plant flavonoids in biology and medicine: biochemical, pharmacological and structure-activity relationships. Alan R. Liss: New York.
3. Cody V, Middleton E, Harborne J.B, Beretz A. (1988). Plant flavonoids in biology and medicine II: biochemical, cellular and medicinal properties. Alan R. Liss: New York.
4. Stankovic B., Jovanovic T., Masic S., Koricanac Z. (1996). Use of palladium(II) chloride as color-forming reagent in spectrophotometric determination of propylthiouracil in aqueous-solution and tablets. Il Farmaco, Vol.51, No.10, pp.679-682.

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