Reactions of 9-substituted guanines with bromomalondialdehyde in aqueous solution predominantly yield glyoxal-derived adducts
作者:Anne-Mari Ruohola、Niangoran Koissi、Sanna Andersson、Ilona Lepistö、Kari Neuvonen、Satu Mikkola、Harri Lönnberg
DOI:10.1039/b405117c
日期:——
Reactions of 9-ethylguanine, 2′-deoxyguanosine and guanosine with bromomalondialdehyde in aqueous buffers over a wide pH-range were studied. The main products were isolated and characterized by 1H and 13C NMR and mass spectroscopy. The final products formed under acidic and basic conditions were different, but they shared the common feature of being derived from glyoxal. Among the 1 : 1 adducts, 1,N2-(trans-1,2-dihydroxyethano)guanine adduct (6) predominated at pH < 6 and N2-carboxymethylguanine adduct (10a,b) at pH > 7. In addition to these, an N2-(4,5-dihydroxy-1,3-dioxolan-2-yl)methylene adduct (11a,b) and an N2-carboxymethyl-1,N2-(trans-1,2-dihydroxyethano)guanine adduct (12) were obtained at pH 10. The results of kinetic experiments suggest that bromomalondialdehyde is significantly decomposed to formic acid and glycolaldehyde under the conditions required to obtain guanine adducts. Glycolaldehyde is oxidized to glyoxal, which then modifies the guanine base more readily than bromomalondialdehyde. Besides the glyoxal-derived adducts, 1,N2-ethenoguanine (5a–c) and N2,3-ethenoguanine adducts (4a–c) were formed as minor products, and a transient accumulation of two unstable intermediates, tentatively identified as 1,N2-(1,2,2,3-tetrahydroxypropano)
(8) and 1,N2-(2-formyl-1,2,3-trihydroxypropano)
(9) adducts, was observed.
研究了 9-乙基鸟嘌呤、2'-脱氧鸟苷和鸟苷与溴丙二醛在水性缓冲液中在宽 pH 范围内的反应。主要产物通过1H和13C NMR和质谱进行分离和表征。在酸性和碱性条件下形成的最终产物不同,但它们具有共同的特征,即衍生自乙二醛。在 1:1 加合物中,pH < 6 时主要为 1,N2-(反式-1,2-二羟基乙醇)鸟嘌呤加合物 (6),pH > 7 时主要为 N2-羧甲基鸟嘌呤加合物 (10a,b)。 N2-(4,5-二羟基-1,3-二氧戊环-2-基)亚甲基加合物 (11a,b) 和 N2-羧甲基-1,N2-(反式-1,2-二羟基乙醇)鸟嘌呤加合物 (12 )在pH 10下获得。动力学实验结果表明,在获得鸟嘌呤加合物所需的条件下,溴丙二醛显着分解为甲酸和乙醇醛。乙醇醛被氧化成乙二醛,然后乙二醛比溴丙二醛更容易修饰鸟嘌呤碱基。除了乙二醛衍生的加合物外,还形成了次要产物 1,N2-乙烯基鸟嘌呤 (5a–c) 和 N2,3-乙烯基鸟嘌呤加合物 (4a–c),以及两种不稳定中间体的短暂积累,初步鉴定为 1,N2 -(1,2,2,3-四羟基丙酸)
(8)和1,N2-(2-甲酰基-1,2,3-三羟基丙酸)
(9)观察到加合物。