Inhibition of NO production by activated microglial cells in response to Af extract. (A) Microglial cells were treated with different concentrations of the extract and concomitantly activated by LPS (4.5 ng/mL) for 20 h. (B) Af extract was added before, concomitant with, or after activation by LPS (4.5 ng/mL). NO levels in cell conditioned supernatants were measured. The results represent means ± SEM of 3 separate experiments (A, n = 9) or 2 separate experiments (B, n = 6). * p < 0.01; ** p < 0.001.