Monoterpenoid Indole Alkaloids from Kopsia officinalis and the Immunosuppressive Activity of Rhazinilam

Six new monoterpenoid indole alkaloids, kopsinidines C–E ( 1 – 3 ), 11,12-methylenedioxychanofruticosinic acid ( 4 ), 12-methoxychanofruticosinic acid ( 5 ), and N (4)-methylkopsininate ( 7 ), as well as chanofruticosinic acid ( 6, as a natural product) and 23 known alkaloids, were obtained from the twigs and leaves of Kopsia officinalis . Their structures were characterized by physical data analysis. All isolated compounds were evaluated for their immunosuppressive activity on human T cell proliferation. Rhazinilam ( 29 ) significantly inhibited human T cell proliferation activated by anti-CD3/anti-CD28 antibodies (IC 50 = 1.0 μM) and alloantigen stimulation (IC 50 = 1.1 μM) without obvious cytotoxicity for naïve human T cells and peripheral blood mononuclear cells (0–320 μM). Although it did not affect T cell activation, it induced T cell cycle arrest in the G 2 /M phase and inhibited proinflammatory cytokine production in activated T cells.