Combining molecular docking and 3-D pharmacophore generation to enclose the in vivo antigenotoxic activity of naturally occurring aromatic compounds: myricetin, quercetin, rutin, and rosmarinic acid.

Considering the controversial results concerning the antimutagenicity of some phenolic compounds recorded in the literature, the antigenotoxic effects of four selected phenolic compounds, myricetin, quercetin, rutin, and rosmarinic acid, against DNA damage induced by alkylation with ethyl methanesulfonate (EMS), were evaluated in Drosophila melanogaster males using the sex-linked recessive lethal (SLRL) test. To assess the protective effects against DNA damage, D. melanogaster males were exposed to a monofunctional alkylating agent EMS in concentration of 0.75 ppm, 24 h prior to one of the selected phenolic compounds in the concentration of 100 ppm. The possible differences in mechanisms of protection by selected compounds were determined by molecular docking, after which structure-based 3-D pharmacophore models were generated. EMS induced considerable DNA damage as shown by significant increase in the frequency of germinative mutations. The frequency decreased with high significance (p<0.001***) after post-treatments with all selected phenolic compounds. Further, docking analysis revealed EMS pre-bond conformations against guanine and thymine as a necessary condition for alkylation, after which resulting O6-ethylguanine and O4-ethylthimine were docked into the active site of O6-alkylguanine-DNA alkyltransferase to confirm that particular lesions are going to be repaired. Finally, myricetin and quercetin protected dealkylated nucleotides from further EMS alkylation by forming the strong hydrogen bonds with O6-guanine and O4-thymine via B ring hydroxyl group (bond lengths lower than 2.5 Å). On the other side, rutin and rosmarinic acid encircled nucleotides and by fulfilling the EMS binding space they made an impermeable barrier for the EMS molecule and prevented further alkylation.

In vivo antigenotoxic potential and possible mechanism of action of selected 4-hydroxy-2H-chromen-2-one derivatives.

The in vivo sex-linked recessive lethal test was carried out in Drosophila melanogaster to investigate whether or not five substituted 4-hydroxy-2H-chromen-2-ones can modulate the genotoxicity of the well-established mutagenic agent ethyl methanesulfonate (EMS). For this purpose, 3 days old Canton S males were treated with the potent mutagen EMS alone in concentration of 0.75 ppm, as well as in combination with one of the five 4-hydroxycoumarins, namely diethyl 2-(1-(4-hydroxy-2-oxo-2H-chromen-3-yl)ethylidene)malonate (2b), 3-(1-(4-hydroxy-2-oxo-2H-chromen-3-yl)ethylidene)pentane-2,4-dione (6b), 4-(4-(4-hydroxy-2-oxo-2H-chromen-3-yl)thiazol-2-ylamino) benzenesulfonic acid (4c), 4-hydroxy-3-(2-(2-nitropheny lamino)thiazol-4-yl)-2H-chromen-2-one (9c), and (E)-4-hydroxy-3-(1-(m-tolylimino)ethyl)-2H-chromen-2-one (5d), in concentration of 70 ppm. The frequency of germinative mutations increased significantly after the treatment with EMS and decreased after treatments with coumarins. The maximum reduction was observed after treatments with 2b, 6b, 4c, and 5d. By the formation of hydrogen bonds or electrostatic interactions with O(6) of DNA guanine, tested coumarins prevent EMS-induced alkylation. The results indicate a protective role of five 4-hydroxycoumarins under the action of a strong mutagen.