engleski

SPECTROPHOTOMETRIC STUDY OF THE RUTHENIUM(III)-QUERCETIN COMPLEX

Quercetin (3&cent ; , 3, 4&cent ; , 5, 7-pentahydroxyflavone) belongs to the group of flavonoids, which are very important plant phenolic compounds, occurring in various kinds of food (fruit and vegetables).[1] The interest in the quercetin is due to its some physiological activities (cytostatic, protects cellular components from oxidative damage and free radical toxicity).[2, 3] The antioxidant properties of quercetin can protect against certain kinds of cancer. Some metal-flavonoides complexes have a more antitumor activity[4], so the past few years have seen a remarkable increase in the scientific interest for research of metal-flavonoid complexes. Complexes of ruthenium have demostrated cytotoxity in cell culture and antitumor activity.[5, 6] Quercetin is a naturally occurring flavonol which has also been used before for spectropfotometric and fluorimetric determination of metal ions.[7] Present paper deals with new spectrophotometric method for the determination of ruthenium with quercetin. Quercetin react in slightly acidic 50% ethanolic media (pH = 4.5 -5.5, acetate buffer) with ruthenium(III) to give a dark-yellow chelate which has an absorption maximum at 422 nm. Ruthenium(III)-quercetin complex forms quantitatively only by heating. The optimum heating time was 20 minutes at 60 0C. The reaction is instantaneous and absorbance remains stable for 4 h. The average molar absorptivity and Sandell&cent ; s sensitivity were found to be 2.7 ´ 104 dm3 mol-1 cm-1, and 0.376 mg of Ru cm-2, respectively. The stoichiometric composition of the chelate is 1:2 (Ru(III) : quercetin). The proposed method was successfully applied to the determination of both ruthenium and quercetin in synthetic mixtures. Literature: [1] "The Flavonoids, Advances in Research Since 1986", Ed.J.H. Harborne, Chapman and Hall. Lodon, 1994. [2] S.D. Skarper, M. Fabris, V. Ferari, F. Dalle Carbonate, A Leon, Free Radic. Biol. Med. 1997, 22, 669. [3] T. Nakayama, M. Yamada, T. Osawa, S. Kawakiski, Biochem. Pharmacol. 1993, 45, 265. [4] J. Zhou, L. Wang, N. Tang, J. Inorg. Biochem. 2001, 83, 41. [5] O. Novakova, J. Kašparkova, O. Vrana, P.M. Vliet, J. Reedijk, V. Brabec, Biochem. 1995, 34, 12369. [6] P.M. van Vliet. S.M.S: Toekimin, J.G. Haasnoot, J. Reedijk, O. Novakova, O. Vrana, V. Brabec, Inorg. Chim. Acta 1995, 231, 57. [7] E.B: Sandell, H. Onishi, Photometric Determination of Traces of Metals-General Aspects, 4th Ed., Wiley, New York, 1978.

Quercetin; Ruthenium; Spectrophotometric determination; Synthetic mixtures

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