The butanolic extract of the leaves of S. odorata was investigated in view of its immunomodulating and free-radical scavenging effects. The immunomodulating activity was assessed in terms of the release of cytokines, like interleukin-1 (IL-1) and tumour necrosis factor-(alpha) (TNF-alpha) from human macrophages using ELISA Method. The release of IL-1 and TNF-alpha from human macrophages was induced by incubation with the butanolic extract for 24 hours at concentrations 20, 40, 50, 100, and 150 ug/ml using 10 ug/ml lipopolysaccharide (LPS) as the positive control. LPS induced the release of 339 ug/ml of IL-1, where as the leaf extract of at 20, 40, 50, 100 and 150 ug/ml released 83, 64, 249, 1612 and 722 ug/ml respectively. On the other hand, 4191 ug/ml TNF-alpha was released by LPS at 10 ug/ml. The leaf extract stimulated the release of 361, 755, 438, 801 and 1118 ug/ml TNF-alpha at 20, 40, 50, 100 and 150 ug/ml of leaf extract respectively.
The free radical scavenging activity of S. odorata was determined using the Electron Spin Resonance Technique (ESR). Briefly, hydroxyl and superoxide radicals were generated in the presence of S. odorata and measured by ESR spin trapping technique. S. Odorata at 1.136 mg/ml scavenged 69.18% of hydroxyl radicals while at 11.63%, almost 100% hydroxyl radicals were scavenged. On the other hand, S. odorata did not show any significant superoxide scavenging effect.