Colletopeptides A–D, Anti-inflammatory Cyclic Tridepsipeptides from the Plant Endophytic Fungus Colletotrichum sp. S8

Four new hybrid peptide-polyketide cyclic tridepsipeptides, colletopeptides A–D (1–4), were isolated and characterized from the endophytic fungus Colletotrichum sp. S8 derived from the stems of Rubia podantha with the guidance of LC-UV-MS detection. Their structures were elucidated by extensive spectroscopic analysis and X-ray crystallography. Compounds 1–4 are rare natural 12-membered cyclic tridepsipeptides containing a 3,5,11-trihydroxy-2-methyl dodecanoic acid unit in their structures. 1–4 inhibited lipopolysaccharide-induced nitric oxide production in RAW264.7 macrophages with the IC50 values of 8.3, 38.7, 13.5, and 22.2 μM, respectively. 1 also inhibited the production of inflammatory factors IL-6 and TNF-α, and decreased the phosphorylation of NF-κB-associated proteins IκBα and p65.