Principle of the bark of Phellodendron amurense to suppress the cellular immune response.

We previously reported that Wen-Qing-Yin (Unsei-in), a traditional Chinese blended medicine, inhibited the induction phase of various kinds of delayed type hypersensitivity (DTH) and local graft-versus-host (GvH) reactions, but did not affect humoral immune responses or the effector phase of DTH in experimental animals. In another report, we demonstrated that Phellodendri Cortex (bark of Phellodendron amurense Rupr. Rutaceae) was a component having the most potent suppressive effect on the cellular immune response among the 8 medical plants composing Unsei-in. In the present study, we isolated OB-1 and OB-5 from Phellodendri Cortex as the biologically active principles to suppress local GvH reactions in mice. OB-1 and OB-5 are quaternary base alkaloids known as magnoflorine and phellodendrine, respectively. They suppressed the local GvH reaction, when given i.p. to the host mice at 5-20 mg/kg for 8 consecutive days from the day of spleen cell transfer to cause the reaction. Both OB-1 and OB-5 suppressed picryl chloride-induced delayed type hypersensitivity (PC-DTH) when given i.p. to mice at 10 and 20 mg/kg for 5 consecutive days from the day of the sensitization, but did not suppress it when given at the time of the challenge. These results suggest that OB-1 and OB-5 suppress the induction phase but not the effector phase of the cellular immune response. They are expected to have a value as a new type of immunosuppressor.