TRAIL-sensitizing Cytochalasins from the Endophytic Fungus Phoma multirostrata

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 Δ13 to Δ21 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.