ObjectiveTo investigate the anti-radiation mechanism and its mechanism of dark tea extract.

MethodsThe mechanism of radiation protection of dark tea extract groups (50 mg/kg, 100 mg/kg, 200 mg/kg) were investigated by 30 days survival rate experiment of ¹³⁷Cs γ-rays irradiated mice, protection of oxidative damage in liver, lung and serum, and TLR5 receptor activation test of HEK-Blue^TM hTLR5 cell after deal with dark tea extract (1 ng/mL, 100 ng/mL).

ResultsIn 30 d survival rate test, average survival time of dark tea extract groups (50 mg/kg, 100 mg/kg, 200 mg/kg) increased from 18.73 d to 23.40 d, 24.07 d and 27.73 d compared with the irradiation-only group, especially in the high dose group (t=3.126, P < 0.05). The survival rate of the high dose group was 53.4% lifted. The results of oxidative damage protection test showed that dark tea extract could increase the activity of superoxide dismutase(t=2.993, P < 0.05; t=4.049, P < 0.01), catalase(t=4.883, P < 0.01) and glutathione peroxidase (t=2.702, 2.959, both P < 0.05) in serum and tissues of mice, and reduce the content of lipid peroxides malondialdehyde(MDA). The dark tea extract polysaccharide could activate the TLR5 receptor when compared with the control group, the difference was sign that dark tea extract can effectively prolong the survival time of mice from 18.73 days to 27.7 days after irradiated with 7.0 Gy γ-rays, the survival rate of mice treated with dark tea siginificant(t=9.222, P < 0.05).

ConclusionThe data suggested that the radiation protection mechanism of dark tea extract may be related to the activation of TLR5 receptor by dark tea polysaccharide.