Down-regulation of MMP-9 activity in activated microglial cells by Af extract. Microglial cells were treated with the indicated concentrations of Af extract, followed by stimulation with LPS (4.5 ng/mL). After 24 h: A. conditioned media were collected and tested for MMP-9 activity by gel zymography. The zymogram represents two independent experiments. B. Cell viability was determined by the crystal violet assay. The histogram represents the means ± SD of two independent experiments (n = 2).