Antibacterial and Antifungal Polyketides from the Fungus <i>Aspergillus unguis</i> PSU-MF16
Praphatsorn Saetang, Vatcharin Rukachaisirikul, Souwalak Phongpaichit, Sita Preedanon, Jariya Sakayaroj, Sarinya Hadsadee, Siriporn Jungsuttiwong
Abstract
Seven new polyketides including a phenol (1), two diphenyl ethers (2 and 3), two depsidones (4 and 5), and two phthalides (6 and 7) were isolated from the fungus Aspergillus unguis PSU-MF16 along with 27 known compounds. Their structures were determined by extensive spectroscopic analysis. The absolute configurations of 1 and 4–7 were established using comparative analyses of calculated and experimental ECD spectra. Among the new metabolites, 2 exhibited the best antimicrobial activity against Staphylococcus aureus, methicillin-resistant S. aureus, and Microsporum gypseum with equal MIC values of 16 μg/mL. In addition, known emeguisin A displayed potent antimicrobial activity against S. aureus, methicillin-resistant S. aureus, and Cryptococcus neoformans with equal MIC values of 0.5 μg/mL, compared with the standard drugs, vancomycin and amphotericin B. The structure–activity relationship study of the isolated compounds for antimicrobial activity is discussed.