Hirtellanines A and B, a pair of isomeric isoflavonoid derivatives from Campylotropis hirtella and their immunosuppressive activities

A pair of isomeric isoflavonoid derivatives, Hirtellanines A (1) and B (2), has been isolated from the roots of Campylotropis hirtella (Franch.) Schindl. and their structures were elucidated on the basis of spectroscopic methods, with special emphasis on 1D and 2D NMR techniques. The in vitro assay showed that Hirtellanine A had strong B lymphocyte suppression activity (IC50: 0.06 μM) and T lymphocyte suppression activity (IC50: 0.92 μM). Hirtellanine B showed moderate B lymphocyte suppression activity (IC50: 3.00 μM) and T lymphocyte suppression activity (IC50: 9.55 μM). Due to the potent immunosuppressive activities and lower cytotoxicity, Hirtellanine A could be a promising lead towards novel immunosuppressive agents.