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 microg/ml
AME before exposure to 3 Gy gamma-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 microg/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 microg/ml
AME before exposure to different doses (0, 0.5, 1, 2, 3 and 4 Gy) of gamma-radiation. The irradiation of HPBLs with different doses of gamma-radiation caused a dose-dependent increase in the frequency of lymphocytes bearing one, two and multiple micronuclei, while treatment of HPBLs with 5 microg/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 microg/ml for the majority of radicals and plateaued thereafter. Our study demonstrates that
AME at 5 microg/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.