Fig. 1

Inhibitory activity of three limonoids isolated from Trichilia welwitschii on nitrix oxide production. The RAW 264.7 macrophages cells were seeded in 96 well-microtitre plates and were activated by incubation in medium containing 1 µg/mL LPS alone (control) or lipopolysaccharide with different concentrations of the samples dissolved in DMSO. Nitric oxide released from macrophages was determined by measuring the nitrite concentration in culture supernatant using the Griess reagent. The concentrations of nitrite were derived from regression analysis using serial dilutions of sodium nitrite as a standard. Percentage inhibition was calculated based on the ability of compounds to inhibit nitric oxide formation by cells compared with the control (cells in media without compounds), which was considered as 0 % inhibition. Data represent the mean ± SE of three independent experiments ∗p < 0.05, ∗p < 0.01 and ∗∗∗p < 0.001 are significantly different from the reference compound quercetin