Fast repair of hydroxy radical purine deoxynucleotide adducts by phenylpropanoid glycosides and their derivatives from Chinese herbs

DNA damaged by oxygen radicals has been implicated as a causative event in a number of degenerative diseases, including cancer and aging. So it is ver y significant to look for ways in which either oxygen radicals are scavenge d prior to DNA damage or damaged DNA is repaired to supplement the cells' i nadequate repair capacity. The repair activities and reaction mechanism of phenylpropanoid glycosides (PPGs) and their derivatives, isolated from Chin ese folk medicinal herbs, towards both dGMP-OH. adducts and dAMP-OH. adduct s were studied with the pulse radiolytic technique. On pulse irradiation of nitrous oxide saturated 2 mM dGMP or dAMP aqueous solution containing one of the PPGs or their derivatives, the transient absorption spectra of the h ydroxyl adduct of dGMP or dAMP decayed with the formation of that of phenox yl radicals of PPGs or their derivatives within several decades of microsec onds after electron pulse irradiation. The result indicated that dGMP or dA MP hydroxyl adducts can be repaired by PPGs or their derivatives. The rate constants of the repair reactions were deduced to be 0.641-1.28 x 10(9) M-1 s(-1) for dGMP-OH. and 0.2-0.491 x 10(9) M-1 s(-1) for dAMP-OH. which posi tively correlated to the number of phenolic hydroxyl groups in the glycosid e structure. A deeper understanding of this new repair mechanism may help r esearchers to design strategies to prevent and/or intervene more effectivel y in free radical related diseases. (C) 1999 Elsevier Science B.V. All righ ts reserved.