Dipeniroqueforins A–B and Peniroqueforin D: Eremophilane-Type Sesquiterpenoid Derivatives with Cytotoxic Activity from Penicillium roqueforti

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Guided by the Global Natural Products Social (GNPS) molecular networking strategy, five undescribed eremophilane-type sesquiterpenoid derivatives ( 1 – 5 ) were isolated and identified from fungus Penicillium roqueforti, which was separated from the root soil of plant Hypericum beanii collected in Shennongjia Forestry District, Hubei Province. Dipeniroqueforins A–B ( 1 – 2 ), representing a lactam-type sesquiterpenoid skeleton with a highly symmetrical and homodimeric 5/6/6–6/6/5 hexacyclic system, are reported within the eremophilane-type family for the first time. Peniroqueforin D ( 5 ) represents the first example of a 1,2- seco eremophilane-type sesquiterpenoid derivative featuring an undescribed 7/6-fused ring system. The structures of these compounds were elucidated by various spectroscopic analyses, DP4+ probability analyses, ECD calculations, and single-crystal X-ray diffraction experiments. Furthermore, these isolates were evaluated for cytotoxicity, and the result uncovered that compound 1 displayed broad-spectrum activity. Further mechanistic study revealed that compound 1 could significantly upregulate the mRNA expression of genes related to the oxidative induction, leading to the abnormal ROS levels in tumor cells and ultimately causing tumor cell apoptosis.