Chem. Pharm. Bull. 55(9) 1383—1384 (2007)

tive secondary metabolites including antifungal macrocyclic polyacetones, antiinsectan indole diterpenoids, and antibacterial polyoxygenated farnesylcyclohexenones. In our continuing search for antimicrobial substances from endophytic fungi isolated from the leaves of Garcinia plants, the crude extract of Penicillium paxilli PSU-A71 exhibited interesting antifungal acitvity against Microsporum gypseum SHMU-4 and showed no activity against pathogenic bacteria (Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa) and other fungi (Candida albicans and Cryptococcus neoformans). M. gypseum, a human pathogenic fungus, causes infections of the skin and scalp (ringworm or tinea or dermatophytosis) and disseminated infections in AIDS patients. Previous investigation of P. paxilli led to the isolation of paxilline, paxisterol and paspaline B. We describe herein the isolation and structural elucidation of one new pyrone derivative, penicillone (1), paxilline, pyrenocines A (2) and B (3) from the broth EtOAc extract of P. paxilli PSU-A71. All isolates were tested for antifungal activity against M. gypseum SH-MU-4. Penicillone (1) had the molecular formula C11H14SO4 by HR-MS. The IR spectrum showed absorption bands for conjugated ester carbonyl (1721 cm ) and conjugated ketone carbonyl (1668 cm ) groups. The C-NMR and DEPT spectra demonstrated that 1 possessed the number and type of carbons identical to 3. In addition, the H-NMR data of 1 were closely related to those of 3 except for the major difference in the chemical shift of H-9 (d 3.62 in 1 and d 4.30 in 3). These suggested that 1 had a pyrone structure with the presence of a SH group, not an OH group, at C-9. This assignment was supported by the carbon resonance of C-9 at d 36.5 and HMBC correlations of H2-8 (d 2.83, dd, J 16.0, 3.0 Hz and d 2.55, dd, J 16.0, 11.5 Hz)/C-7 (d 191.7), C-9 and C-10 (d 19.7). The location of an olefinic proton (d 5.29, s) and a methoxyl group (d 3.76, s) at C-3 and C-4 of the pyrone unit, respectively, was confirmed on the basis of HMBC correlations of H-3/C-2 (d 168.7), C-4 (d 168.7) and C-5 (d 128.9) and that of the methoxy protons (H3-11)/C-4. However, in the UV spectrum, a strong absorption band at longer wavelenght than that in 3 (lmax 285 nm) revealed the presence of a longer conjugated chromophore. Analysis of the C-NMR spectrum revealed that C-2, C-3 (d 94.5) and C-5 in 1 resonated at lower field than those in 3. In contrast, C-6 (d 156.6) in 1 appeared at higher field. Irradiation of the methoxy protons in the NOEDIFF experiment enhanced signal intensity of H-3 (d 5.29, s) and H3-12 (d 2.04, s), thus indicating the attachment of the methyl group in 1 at C-5, not at C-6 as found in 3. The HMBC correlations of H3-12/C-4, C-5 and C-6 confirmed the assigned location. The remaining 1-oxobutyl group was then located at C-6. This would affect the chemical shift of carbons in the pyrone skeleton as well as the UV absorption band due to the resonance effect and extended conjugation. Consequently, 1 was identified as a new thiol. All pyrone isolates were tested for antifungal activity against M. gypseum SH-MU-4. Pyrenocine B (3) showed mild activity with a MIC value of 32 mg/ml while penicillone (1) and pyrenocine A (2) were much less active than 3 with MIC values of 64 and 128 mg/ml, respectively.