Immunosuppressive iridoids from the fruits of Gardenia jasminoides.

A new iridoid, gardaloside (1), and a new safranal-type monoterpene, jasminoside G (2), together with 10 known compounds including nine iridoids and a second safranal-type monoterpene, were isolated from the fruits of Gardenia jasminoides. The structures of 1 and 2 were established on the basis of spectroscopic evidence. Of these compounds, geniposide (3), 6alpha-hydroxygeniposide (5), ixoroside (7), and shanzhiside (8) showed significant inhibition of IL-2 secretion by phorbol myristate acetate and anti-CD28 monoclonal antibody co-stimulated activation of human peripheral blood T cells.