DeepSAT-Driven Discovery of Pimarane Diterpenoids from Arthrinium arundinis with Ulcerative Colitis Inhibitory Activity via NF-κB/MAPK Pathways

Utilizing HSQC-based DeepSAT analysis, nine undescribed pimarane diterpenoids were isolated from Arthrinium arundinis. Structurally, compounds 1 and 2 represent the first pimarane diterpenoids characterized by an aromatic A-ring system and a 1,6-dioxaspiro[4.4]nonan-4-one core. Compound 3 represents the first pimarane–kojate conjugate. Their structures were elucidated by comprehensive spectroscopic analysis, single-crystal X-ray diffraction (XRD) analyses, Mo2(OAc)4-induced circular dichroism (ICD), and electronic circular dichroism (ECD) calculations. Compound 9 alleviates dextran sodium sulfate (DSS)-induced ulcerative colitis (UC) in mice by inhibiting NF-κB/MAPK pathways.