Antioxidant and Radioprotective Effects of Ocimum Flavonoids Orientin and Vicenin in Escherichia coli

Vrinda Nayak; Hajime Nishioka; P. Uma Devi

doi:10.14429/dsj.56.1881

Vrinda Nayak University of Bristol, Bristol
Hajime Nishioka Kyoto Institute for Bioscience, Kyoto
P. Uma Devi Jawaharlal Nehru Cancer Hospital & Research Centre, Bhopal

DOI: https://doi.org/10.14429/dsj.56.1881

Keywords: Escherichia coli, Escherichia coli mutants DSH19 and DSH56, orientin, vicenin, radioprotection, antioxidant effect, Ocimum flavonoids, reactive oxygen species

Abstract

Antioxidant effect of the Ocimum flavonoids, orientin and vicenin (25-500 M), was evaluated
by the kat-sod assay in Escherichia coli mutants (DSH56, superoxide dismutase-deficient and
DSH19, catalase-deficient) treated with 50 mM menadione or H2O2 (1mM). Protection by orientin
(200 M) and vicenin (200 M) against H2O2-induced DNA damage in DSH19 cells ( -galactosidase
test) and against radiation lethality in wild-type (DSH7) and DSH19 cells exposed to 0-150 Gy
gamma radiation was also studied. Menadione and H2O2 reduced the surviving fraction to 0.2
and 0.4 in DSH56 and DSH19 cells, respectively. Even 25 M of either flavonoid significantly
increased the surviving fraction, with maximum protection at 200 M. H2O2 increased the -
galactosidase activity in a concentration-dependent manner, which was significantly
(P < 0.050–0.001) reduced by orientin and vicenin (200 M). Radiation produced a dose-dependent
decrease in the surviving fraction of both DSH7 and DSH19 cells. Pretreatment with 200 M
orientin or vicenin significantly increased the survival (DRF: DSH7 = 2.2; DSH19 = 1.8). Both
compounds were equally effective in reducing the cytotoxicity of radiation and the chemical
oxidants. The cytoprotective action of these plant flavonoids could be ascribed to their free
radical scavenging activity.