Inhibition of Interleukin-4 and β-Hexosaminidase Release in RBL-2H3 Cells by Compounds Isolated from Lobelia chinensis

ABSTRACT

Lobelia chinensis Lour. has commonly been used in traditional Chinese medicine for the treatment of antidote, diuretic, diarrhea, and inflammation. This study aimed to identify the active compounds in an aqueous extract of L. chinensis responsible for its anti-atopic effect in vitro using RBL-2H3 cells. A chemical investigation of secondary metabolites in an aqueous extract of L. chinensis led to the isolation of nine chemical constituents, which included the four marker compounds, and these were evaluated for their inhibitory effects on IL-4 mRNA expression and the release of β-hexosaminidase in propidium iodide-induced RBL-2H3 cells. We found diosmetin and fraxidin inhibited cellular IL-4 mRNA expression, and that diosmetin and 6,8-dimethoxycoumarin inhibited DNP-specific IgE-induced degranulation in these cells. Our study suggests that diosmetin, fraxidin, and 6,8-dimethoxycoumarin are potential candidates for the treatment of atopic diseases.