TRAIL-sensitizing Cytochalasins from the Endophytic Fungus Phoma multirostrata

ABSTRACT Seven undescribed cytochalasins, multirostratins K – Q (2–8), together with one known analogue, cytochalasin Z3 (1), were isolated from the culture of Phoma multirostrata XJ-2-1, an endophytic fungus obtained from the root of Parasenecio albus. Their structures with absolute configurations were determined by 1D and 2D NMR, high-resolution electrospray ionization mass spectrometry (HRESIMS), electronic circular dichroism (ECD), single-crystal X-ray crystallography, and chemical methods. The structure of ascochalasin was revised from Δ 13 to Δ 21 by detailed analysis of the NMR data and by comparison with the data for 7. In a TRAIL (tumor necrosis factor related apoptosis inducing ligand)-resistance-overcoming experiment, co-treatment of 2 or 6 with TRAIL reduced the cell viability of A549 cells by 30.3% and 27.5% at 10 µM, respectively.