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.
Biological herbicides have received much attention due to their abundant resources, low development cost, unique targets and environmental friendliness. This study reveals some interesting effects of mycotoxin cytochalasin A (CA) on photosystem II (PSII). Our results suggested that CA causes leaf lesions onAgeratina adenophoradue to its multiple effects on PSII. At a half-inhibitory concentration of 58.5 μΜ (I50, 58.5 μΜ), the rate of O2evolution of PSII was significantly inhibited by CA. This indicates that CA possesses excellent phytotoxicity and exhibits potential herbicidal activity. Based on the increase in the J-step of the chlorophyll fluorescence rise OJIP curve and the analysis of some JIP-test parameters, similar to the classical herbicide diuron, CA interrupted PSII electron transfer beyond QAat the acceptor side, leading to damage to the PSII antenna structure and inactivation of reaction centers. Molecular docking model of CA and D1 protein ofA. adenophorafurther suggests that CA directly targets the QBsite of D1 protein. The potential hydrogen bonds are formed between CA and residues D1-His215, D1-Ala263 and D1-Ser264, respectively. The binding of CA to residue D1-Ala263 is novel. Thus, CA is a new natural PSII inhibitor. These results clarify the mode of action of CA in photosynthesis, providing valuable information and potential implications for the design of novel bioherbicides.Keywords:natural product;bioherbicide;photosynthetic inhibitor;chlorophyllafluorescence;D1 protein;molecular docking
危险品化学品经营许可证（带存储）