Phloroglucinols with Immunosuppressive Activitiesfrom the Fruits of Eucalyptus globulus

Five new phloroglucinol derivatives, eucalyptins C–G (1–5), together with 13 known analogues (6–18) were isolated from the fruits of Eucalyptus globulus. The structures and absolute configurations of 1–5 were established by means of spectroscopic data analysis, computational calculation methods, and single-crystal X-ray diffraction. Compounds 1–18 were investigated for their immunosuppressive effects in vitro, and 1, 2, 6, and 7 displayed moderate inhibitory activities with IC50 values of 11.8, 10.2, 18.2, and 19.1 μM, respectively. The stimulation index (SI) of 1 was 64.2 and was compared to that of cyclosporine A (SI = 149.57). Further study demonstrated that 1 exhibited an immunosuppressive effect through inducing apoptosis and inhibiting cytokine secretion.