New Naphtho-γ-Pyrones Isolated from Marine-Derived Fungus Penicillium sp. HK1-22 and Their Antimicrobial Activities

Abstract

Three novel monomeric naphtho-γ-pyrones, peninaphones A–C (compounds 1–3), along with two known bis-naphtho-γ-pyrones (compounds 4 and 5) were isolated from mangrove rhizosphere soil-derived fungus Penicillium sp. HK1-22. The absolute configurations of compounds 1 and 2 were determined by electronic circular dichroism (ECD) spectra, and the structure of compound 3 was confirmed by single-crystal X-ray diffraction analysis. Compounds 4 and 5 are a pair of hindered rotation isomers. A hypothetical biosynthetic pathway for the isolated monomeric and dimeric naphtho-γ-pyrones is also discussed in this study. Compounds 1–3 showed antibacterial activity against Staphylococcus aureus (ATCC 43300, 33591, 29213, and 25923) with minimum inhibitory concentration (MIC) values in the range of 12.5–50 μg/mL. Compound 3 exhibited significant activity against the rice sheath blight pathogen Rhizoctonia solani.