SPECTROMETRIC PK DETERMINATION OF DAPHNETIN, CHLOROGENIC ACID AND QUERCETIN

Polyphenols play an important role in the 'immune system' of plants. S ince their charge is important for their physiological effect it is im portant to know their pK(i) values. Therefore, the pK(i) values of som e plant contents such as daphnetin (pK = 7.36), chlorogenic acid (pK a pproximate to 8.5), and quercetin (pK(1) = 7.03, pK(2) = 9.15) were de termined in the pH range 7-10 using UV/VIS spectroscopy. The decomposi tion kinetics of quercetin in alkaline solutions was taken into consid eration by extrapolating the absorbance time curves to time zero (t = 0). The graphic method of absorbance (A) diagrams was used to determin e the pK(i) values. In the case of quercetin the method of linear regr ession was also used for the determination.