Identification of the compounds in Ku Shen (Sophora flavescentis), an active constituent of ASHMI (Anti-asthma Herbal Medicine Intervention) that inhibit IgE synthesis

Abstract

[Rationale]: Previous experiments demonstrated that the ASHMI constituent Ku Shen inhibited IgE production by a human myeloma B cell line (IC50= 45.68 μg/mL). This herb was fractionated into 8 different fractions (KSF1-KSF8) with respect to polarity and acidic vs basic properties. KSF1 (a flavanoid rich fraction) showed the strongest inhibition of IgE secretion (IC50=10.41 μg/mL). The aim of this study was to identify the compounds in KSF1 responsible for this suppression. [Methods]: KSF1was sub-fractionated by preparative reverse-phase high performance liquid chromatography (RP-HPLC) into four fractions (KSF1a, b, c, and d). These fractions were tested for reduction of IgE production by a human myeloma B-cell line cultured at 2x105 cells/mLfor 6 days. IgE levels in supernatants were quantified by Immunocap. [Results]: Among KSF1 sub-fractions, KSF1a had no effect on IgE production. Sub-fractions b, c and d inhibited IgE secretion in a dose dependent manner (KSF1c IC50 value 1.33 μg/mL, KSF1b IC50 value 2.32 μg/mL and KSF1d IC50 value 8.16 μg/mL). No cytotoxicity was detected using MTT assay. [Conclusion]: KSF1c fraction contains the compounds most responsible for the anti-IgE effects of Ku Shen. This fraction will be further investigated to elucidate the chemical structures of the compounds most responsible for the anti-IgE activity of Ku Shen