Ethnopharmacological relevance Ocimum gratissimum L. is a herbaceous plant that has been reported in several ethnopharmacological surveys as a plant readily accessible to the communities and widely used for the treatment of inflammatory diseases. The main goal of this study was to investigate the in vitro and in vivo anti-inflammatory activity and mechanism of action of the ethylacetate fraction of O. gratissimum leaf (EAFOg) and to chemically characterize this fraction. Materials and methods EAFOg was obtained from a sequential methanol extract. The safety profile was evaluated on RAW 264.7 cells, using the alamarBlue® assay. Phenolic contents were determined by spectrophotometry, and metabolites quantified by high performance liquid chromatography. The anti-inflammatory activity of EAFOg and its ability to acts on leucocytes infiltration, inflammatory mediators as NO, IL-1β, TNF-α, and IL-10 in lipopolysaccharide-induced peritonitis in mice and LPS-stimulated RAW 264.7 macrophage were evaluated. In addition, the anti-inflammatory activity of EAFOg was also investigated in arachidonic acid-related enzymes. Results Total phenolic and flavonoid contents of EAFOg were 139.76±1.07 mg GAE/g and 109.95±0.05 mg RE/g respectively. HPLC analysis revealed the presence of rutin, ellagic acid, myricetin and morin. The fraction exhibited no cytotoxic effects on the RAW 264.7 cells. The EAFOg (10, 50 and 200 mg/kg) significantly reduced (p<0.05) neutrophils (38.8%, 58.9%, and 66.5%) and monocytes (38.9%, 58.0% and 72.8%) in LPS-induced peritonitis. Also, EAFOg (5, 20 and 100 µg/mL) produced significant reduction in NO, IL-1β, and TNF-α in RAW 264.7 cells. However, IL-10 level was not affected by the EAFOg, and it preferentially inhibits COX-2 (IC50 =48.86±0.02 µg/mL) than COX-1 and 15-LO (IC50 >100 µg/mL). Conclusion The flavonoid-rich fraction of O. gratissimum leaves demonstrated anti-inflammatory activity via mechanisms that involves inhibition of leucocytes influx, NO, IL-1β, and TNF-α in vivo and in vitro, thus supporting its therapeutic potential in slowing down inflammatory processes in chronic diseases.
