Modulatory Effect of Betulinic Acid on DNA Damage

The following four mutagens with different mechanisms of action were used to study the modulatory effect of BA on DNA damage: (i) methyl methanesulfonate (MMS; Sigma-Aldrich) dissolved in phosphate-buffered saline (PBS) at a concentration of 400 μM [11 (link)]. MMS is a direct-acting monofunctional alkylating agent that reacts with the DNA molecule by transferring methyl radicals [12 (link)]; (ii) doxorubicin (DXR; Eurofarma Laboratórios Ltda.) dissolved in sterile distilled water and used at a concentration of 0.3 μM [13 (link)]. DXR, one of the most potent broad-spectrum antitumor anthracycline antibiotics, is a free radical generator and a potent inhibitor of topoisomerase II [14 (link)]; (iii) (S)-(+)-camptothecin (CPT; Sigma-Aldrich) dissolved in DMSO (Sigma-Aldrich) at a concentration of 123.4 μM CPT acts by inhibiting topoisomerase I, an enzyme necessary for DNA replication [15 (link)]; (iv) etoposide (VP-16; Sigma-Aldrich) dissolved in DMSO at a concentration of 1.7 μM. VP-16 is a potent anticancer agent that inhibits topoisomerase II [16 (link)].