Evaluation of the radioprotective effect of Aegle marmelos (L.) Correa in cultured human peripheral blood lymphocytes exposed to different doses of γ-radiation: A micronucleus study

The radioprotective effect of a hydroalcoholic extract of Aegle marmelos (AME) was evaluated in cultured human peripheral blood lymphocytes (HPBLs) by the micronucleus assay. The optimum protective dose of the extract was selected by treating HPBLs with 1.25, 2.5, 5, 6.25, 10, 20, 40, 60, 80 and 100 μg/ml AME before exposure to 3 Gy γ-radiation and then evaluating the micronucleus frequency in cytokinesis blocked HPBLs. Treatment of HPBLs with different doses of AME reduced the frequency of radiation-induced micronuclei significantly, with the greatest reduction in micronucleus induction being observed for 5 μg/ml AME. Therefore, this dose of AME was considered as the optimum dose for radioprotection and further studies were carried out treating the HPBLs with 5 μg/ml AME before exposure to different doses (0, 0.5, 1, 2, 3 and 4 Gy) of γ-radiation. The irradiation of HPBLs with different doses of γ-radiation caused a dose-dependent increase in the frequency of lymphocytes bearing one, two and multiple micronuclei, while treatment of HPBLs with 5 μg/ml AME significantly reduced the frequency of lymphocytes bearing one, two and multiple micronuclei when compared with the irradiated control. The dose-response relationship for both groups was linear. To understand the mechanism of action of AME separate experiments were conducted to evaluate the free radical scavenging of OH, O₂^-, DPPH, ABTS⁺ and NO in vitro. AME was found to inhibit free radicals in a dose-dependent manner up to a dose of 200 μg/ml for the majority of radicals and plateaued thereafter. Our study demonstrates that AME at 5 μg/ml protected HPBLs against radiation-induced DNA damage and genomic instability and its radioprotective activity may be by scavenging of radiation-induced free radicals and increased oxidant status.