Abstract: Three previously undescribed cytochalasins, named xylariasins A-C (1-3), together with six known ones (4-9) were isolated from Xylaria sp. CFL5, an endophytic fungus of Cephalotaxus fortunei. The chemical structures of all new compounds were elucidated on the basis of extensive spectroscopic data analyses and electronic circular dichroism calculation, as well as optical rotation calculation. Biological activities of compounds 1, 4-9 were evaluated, including cytotoxic, LAG3/MHC Ⅱ binding inhibition and LAG3/FGL1 binding inhibition activities. Compounds 6 and 9 possessed cytotoxicity against AGS cells at 5 μM, with inhibition rates of 94% and 64%, respectively. In addition, all tested isolates, except compound 6, exhibited obvious inhibitory activity against the interaction of both LAG3/MHC Ⅱ and LAG3/FGL1. Compounds 1, 5, 7, and 8 inhibited LAG3/MHC Ⅱ with IC₅₀ values ranging from 2.37 to 4.74 μM. Meanwhile, the IC₅₀ values of compounds 1, 7, and 8 against LAG3/FGL1 were 11.78, 4.39, and 7.45 μM, respectively.

Key words: Cytochalasin, Xylaria sp., Cephalotaxus fortunei, LAG3/MHC II binding inhibition, LAG3/FGL1 binding inhibition

摘要： Three previously undescribed cytochalasins, named xylariasins A-C (1-3), together with six known ones (4-9) were isolated from Xylaria sp. CFL5, an endophytic fungus of Cephalotaxus fortunei. The chemical structures of all new compounds were elucidated on the basis of extensive spectroscopic data analyses and electronic circular dichroism calculation, as well as optical rotation calculation. Biological activities of compounds 1, 4-9 were evaluated, including cytotoxic, LAG3/MHC Ⅱ binding inhibition and LAG3/FGL1 binding inhibition activities. Compounds 6 and 9 possessed cytotoxicity against AGS cells at 5 μM, with inhibition rates of 94% and 64%, respectively. In addition, all tested isolates, except compound 6, exhibited obvious inhibitory activity against the interaction of both LAG3/MHC Ⅱ and LAG3/FGL1. Compounds 1, 5, 7, and 8 inhibited LAG3/MHC Ⅱ with IC₅₀ values ranging from 2.37 to 4.74 μM. Meanwhile, the IC₅₀ values of compounds 1, 7, and 8 against LAG3/FGL1 were 11.78, 4.39, and 7.45 μM, respectively.

关键词: Cytochalasin, Xylaria sp., Cephalotaxus fortunei, LAG3/MHC II binding inhibition, LAG3/FGL1 binding inhibition