Salacia pallescens Oliv. (Celastraceae) Scavenges Free Radicals and Inhibits Pro-inflammatory Mediators in Lipopolysaccharide-activated RAW Cells 264.7 Macrophages

Objectives: Salacia pallescens has folkloric anti-inflammatory claims, with little scientific investigation. Hence, the antioxidant and anti-inflammatory effects along with phytochemical components of the plant were investigated. Materials and Methods: The antioxidant property of S. pallescens leaf (SPL) methanol extract was evaluated using 1,1-diphenyl-2-picrylhydrazyl and nitric oxide inhibition assays. The anti-inflammatory property of SPL in lipopolysaccharide-stimulated RAW 264.7 macrophages was determined. The cytotoxicity of SPL was assessed in brine shrimp lethality assay (BSL) and against RAW 264.7 cells in a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide based assay. Gas chromatography-mass spectrometry was employed to identify SPL phytochemical compounds. Results: SPL significantly scavenged free radical generated in the antioxidant assays and inhibited nitrite production in stimulated RAW 264.7 cells. Similarly, there was a 9-fold reduction in interleukin-6 produced in RAW 264.7 cells when exposed to the highest concentration of SPL. In addition, 50% lethal concentration of SPL was 455.58 +/- 82.35 mu g/mL while cyclophosphamide gave 16.3 +/- 0.15 mu g/mL in BSL test. Moreover, cell viability was not affected by SPL. Sixteen compounds were identified from SPL where thymol (29.79%), 3-carene (15.97%), and p-cymene (12.19%) are the most abundant. Conclusion: Methanol extract of SPL showed antioxidant and anti-inflammatory activities by free radicals and cytokines inhibition. The activity observed may be related to the polyphenolic compounds in the plant.