Carboline alkaloids from Psammosilene tunicoides and their cytotoxic activities.

Five new carboline alkaloids, tunicoidines A-E ( 1- 5), and two known carboline alkaloids, 1-acetyl-β-carboline-3-carboxylic acid ( 6) and 1-acetyl-3-carbomethoxyl- β-carboline ( 7), were isolated for the first time from the root of Psammosilene tunicoides. The structures of the new carboline alkaloids were established on the basis of 1D- and 2D-NMR, and HR-MS spectroscopic analyses. The seven compounds were evaluated for cytotoxicity against A549, HCT116, ZR-75-30, and HL-60 cell lines. However, only compound 7 had potent cytotoxic activity against the HCT116 cell line with an IC (50) value of 9.67 µg/mL, while the others showed no cytotoxic activities against the four tested cell lines.