Protective effect of isoflavones from Trifolium pratense on dopaminergic neurons.

In the present study, protective effect of five isoflavones (formononetin, daidzein, pratensein, calycosin and irilone) from Trifolium pratense on lipopolysaccharide-induced dopaminergic neurodegeneration was studied for the first time. The results showed that all five isoflavones attenuated LPS-induced decrease in dopamine uptake and the number of dopaminergic neurons in a dose-dependent manner in rat mesencephalic neuron-glia cultures. Moreover, they also significantly inhibited LPS-induced activation of microglia and production of tumor necrosis factor-alpha, nitric oxide and superoxide in mesencephalic neuron-glia cultures and microglia-enriched cultures. In addition, the rank order of protective potency of five isoflavones was: pratensein>daidzein>calycosin>formononetin>irilone. This study suggested that all five isoflavones protected dopaminergic neurons against LPS-induced injury through inhibition of microglia activation and proinflammatory factors generation.