Penicillitone, a Potent <i>in Vitro</i> Anti-inflammatory and Cytotoxic Rearranged Sterol with an Unusual Tetracycle Core Produced by <i>Penicillium purpurogenum</i>

A rearranged sterol with an unusual tetracycle core skeleton, penicillitone (1), and a new sterol, penicillisterol (2), were obtained from the culture of the fungus Penicillium purpurogenum SC0070. Their structures were characterized by spectroscopic analysis, DFT/TDDFT compuations, and X-ray diffraction. Compound 1 demonstrated potent inhibitory effects on tumor cell growth and key pro-inflammatory cytokine production in macrophages. A biogenetic pathway with oxidative cleavage and vinylogous aldol addition as key reactions is proposed for 1.