High electron transfer capacity of thio-derivatives of tea catechins measured using a water soluble stable free radical and their effects on colon cancer cells

Abstract

The antiradical capacity of cysteamine- and cysteine-flavan-3-ol derivatives of green tea catechins bearing the pyrogallol moiety was evaluated using two stable triphenylmethyl radicals, the tri-potassium salt of a tris(4-hydroxysulfonyltetrachlorophenyl)methyl radical (K₃TSPTM) and a tris(2,4,6-trichloro-3,5-dinitrophenyl)methyl radical (HNTTM), as chemosensors in a buffer solution at pH 7 and in the CHCl₃–MeOH mixture (2 : 1, v/v), respectively. The different results obtained using HNTTM or K₃TSPTM lie in the chemical nature of these radicals and, therefore, in their reduction potentials, and in the solvent used in the experiments. The K₃TSPTM radical was selectively sensitive to the pyrogallol moiety in water like TNPTM was in organic solvents, and as a chemosensor is closer to the biological processes by using aqueous media as solvent. The new radical is a useful tool to detect highly reactive phenolic positions that are also the most biologically active as shown by the results on the viability and apoptosis of the colon adenocarcinoma cell line HT-29.