Citrinsorbicillin A, a Novel Homotrimeric Sorbicillinoid Isolated by LC-MS-guided with Cytotoxic Activity from the Fungus Trichoderma Citrinoviride HT-9

Citrinsorbicillin A (1), a novel homotrimeric sorbicillinoid, along with two new monomers citrinsorbicillins B (2) and C (3), were isolated from the Coptis chinensis endophyte Trichoderma citrinoviride HT-9 by liquid chromatograph mass spectrometer (LC-MS)-guided strategy. 1 was the first trimeric-example from terrestrial fungi, which possessed a unique carbon skeleton with two bicyclo[2.2.2]octanedione ring connected through an enolated carbon forming by [4 + 2] cycloaddition. Their structures were elucidated by spectroscopic analysis and X-ray diffraction. 1 exhibited moderate cytotoxicity against human colon cancer H-29 cells, and it induced significant cell cycle arrest by reducing the protein expression of cyclin D1.