Cytochalasins from Xylariasp. CFL5, an Endophytic Fungus of Cephalotaxus fortunei

Abstract: Three previously undescribed cytochalasins, named xylariasins A‒C (1‒3), together with six known ones (4‒9) were isolated from Xylariasp. 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, 4‒9were evaluated, including cytotoxic, LAG3/MHC II binding inhibition and LAG3/FGL1 binding inhibition activities. Compounds 6and 9possessed 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 8inhibited LAG3/MHC II with IC₅₀values ranging from 2.37 to 4.74 μM. Meanwhile, the IC₅₀values of compounds 1, 7, and 8against LAG3/FGL1 were 11.78, 4.39, and 7.45 μM, respectively. Graphic Abstract: <fig id="Figa" position="anchor"> <graphic position="anchor" specific-use="HTML" mime-subtype="PNG" href="MediaObjects/13659_2020_279_Figa_HTML.png" id="MO100"></graphic> </fig>