Penicitrisochromans A-C, new isochromans from the marine-derived fungus <i>Penicillium citrinum</i> PSU-MF100

Three new isochroman derivatives, penicitrisochromans A-C (<b>1</b>-<b>3</b>), together with 25 known polyketides were isolated from the marine-derived fungus <i>Penicillium citrinum</i> PSU-MF100. Their structures were elucidated by extensive spectroscopic analysis. The absolute configurations of <b>1</b> and <b>2</b> were established by comparison of specific rotations and electronic circular dichroism (ECD) data with those of the known co-metabolite whereas those of <b>3</b> were assigned based on the ECD calculation and biosynthetic consideration. Among the isolated polyketides, three known anthraquinone derivatives, <i>ω</i>-hydroxyemodin, penicillanthranin A and emodin, displayed moderate to strong antibacterial activity against methicillin-resistant <i>Staphylococcus aureus</i> with MIC values of 32, 16 and 4 <i>µ</i>g/mL, respectively. For antifungal activity, two known benzopyranones, coniochaetones A and C, exhibited moderate antifungal activity against <i>Candida albicans</i> NCPF3153 and <i>Cryptococcus neoformans</i> ATCC90112 with the respective MIC values of 16 and 64 <i>µ</i>g/mL.