Inhibition of nitric oxide production by Solanum melongena and Solanum macrocarpon on RAW 264.7 cells

Abstract

Nitric oxide (NO) plays an important role in the physiology and pathophysiology of disease. Overproduction of NO is associated with chronic inflammatory diseases and cancers. Several species of Solanaceae have been used traditionally to treat inflammatory-related diseases. To analyse the possible anti-inflammatory properties of these species, the Griess assay was used to evaluate the effects of various Solanum melongena and Solanum macrocarpon extracts on NO production in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. The cytotoxicity of the extracts on the cell line was tested using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Extracts that significantly inhibited NO production were further evaluated for inducible nitric oxide synthase (iNOS) expression by Western blot. Thin-layer chromatography was used to determine the major compounds in the extracts. All extracts significantly inhibited NO production in LPS-stimulated RAW 264.7 cells in a dose-dependent manner. At 200 µg/ml, ethyl acetate extract of S. macrocarpon showed the highest NO inhibition of 81%, with a median inhibitory concentration (IC50) value of 44.78 ± 0.04 µg/ml. The viability of cells treated with the extracts was greater than 80%. Ethanol and ethyl acetate extracts of S. melongena, together with ethanol, hexane and ethyl acetate extracts of S. macrocarpon, reduced iNOS expression significantly. At 200 µg/ml, ethyl acetate extract of S. macrocarpon inhibited iNOS protein expression by 79%. Phytochemical analysis of the extracts showed that fluorescent, double-bond compounds, phenols, flavonoids and terpenoids were mainly present in the extracts. Taken together, the results show the potential of ethanol and ethyl acetate extracts of S. melongena, and hexane and ethyl acetate extracts of S. macrocarpon, as agents for the prevention and treatment of inflammatory-related diseases.