The identities of the adducts formed on reaction of the model electrophilic and carcinogenic esters 1′-acetoxysafrole or 1′-acetoxyestragole with deoxyguanosine in vitro and those formed in vivo in the hepatic DNA of 12-day-old male C57BL/6 × C3H/He F1 (hereafter called B6C3F1) mice treated with 1′-hydroxysafrole or 1′-acetoxysafrole were investigated further with more discriminating high-performance liquid chromatgraphy systems than previously used. The adducts formed from the reactions of 1′-acetoxysafrole or 1′-acetoxyestragole are strictly analogous and are distinguished by the prefixes S and E, respectively. Five adducts, including S(E)-II identified by Phillips et al. (Cancer Res., 41: 176–186, 2664–2671, 1981) as N2-(trans-isosafrol-3′-yl)deoxyguanosine and the analogous isoestragole derivative, have been characterized from the reactions with each ester. Adducts S-I and E-I, tentatively identified by Phillips et al. as N2-(safrol-1′-yl)- or N2-(estragol-1′-yl)deoxyguanosine, were each resolved into a pair of diastereomers. The proposed structures for each diastereomer were confirmed by nuclear magnetic resonance and circular dichroism spectroscopy. Two new adducts, i.e., S(E)-V and S(E)-VI, were isolated from each reaction mixture. On the basis of their pKas, their loss of 3H from [8-3H]deoxyguanosine, their retention of 3H from [1′,2′-3H]deoxyguanosine, and their nuclear magnetic resonance spectra, Adducts S-V and E-V were characterized as 8-(trans-isosafrol-3′-yl)- and 8-(trans-isoestragol-3′-yl)deoxyguanosine, respectively. Adducts S-VI and E-VI were characterized in a similar manner as 7-(trans-isosafrol-3′-yl)- and 7-(trans-isoestragol-3′-yl)guanine, respectively. Adducts S-III and E-III, minor components described in the earlier studies, were not observed in the present work. High-performance liquid chromatography of hydrolysates of the hepatic DNA of male 12-day-old B6C3F1 mice killed 9 h after a single dose (0.1 µmol/g body weight) of [2′,3′-3H]-1′-hydroxysafrole showed that Adducts S-Ia, S-Ib, S-II, S-IV (identified by Phillips et al. as N6-(trans-isosafrol-3′-yl)deoxyadenosine), S-V, and S-VI were present at average levels of 3.5, 7.0, 24.4, 2.9, 1.2, and 3.6 pmol/mg DNA, respectively. Similar levels of these adducts were found in the hepatic DNA after administration of the same dose of [2′,3′-3H]-1′-acetoxysafrole under identical conditions.
This work was supported by Grants CA-07175, CA-22484, and CA-09135 of the National Cancer Institute, USPHS.