A meroterpenoid, chevalone B, was obtained from the Cucumaria japonica-derived fungus Aspergillus sp. H30, which was collected from the South China Sea. The structure was determined by the analysis of nuclear magnetic resonance (NMR) spectroscopic and X-ray data. This is the first report of the crystallographic data and absolute stereochemistry of chevalone B, which was shown to have weak antibacterial activity.

One new phenolic derivative, 1-(4',5'-dihydroxy-2'-methylphenyl)-pentane-1,4-dione (1), along with eighteen known compounds including eight sesquiterpenoids (2–9), one triterpenoid (10), one bisdpoxylignan (11), one coumarin (12), and seven flavonoids (13–19) were isolated from the dried inflorescence of Tibetan herbal medicine Pulicaria insignis. The structure of 1 was established by spectroscopic methods, including HRESIMS, IR, 1D, and 2D NMR. All isolates were assessed for the cytotoxic activities against MGC-803, T24, HepG2, and HeLa cell lines using the MTT assay. The results showed that compound 1 displayed moderate cytotoxicity against Hela and HepG2, and compounds 3, 4, 5, 6, and 13 exhibited potential cytotoxic activities against the four cell lines with IC50 values ranging from 3.05 to 14.37 μM. Notably, compound 5 exhibited significant anti-proliferative activities against HepG2 cell lines with the IC50 values of 3.05 ± 0.36 μM. Further bioactivity investigation showed that compound 5 could block HepG2 cells in the G1 phase of the cell cycle, thereby inhibiting the growth of HepG2 cells and inducing apoptosis in HepG2 cells.

Cycloaddition reactions such as intramolecular Diels-Alder (IMDA) are extremely important in constructing multicyclic scaffolds with diverse bioactivities. Using MycB as a biomarker, three new polyketides-Chaetolivacines A (1), B (3), and C (4)with one known compound Myceliothermophin E (2) comprising of decalin and 4-hydroxy-2-pyridones were obtained from the culture of Chaetomium olivaceum SD-80A under the guidance of gene mining. The structures of these compounds were established using detailed 1D, 2D NMR, and high-resolution electron spray ionization mass spectroscopy (HRESIMS) analysis. The relative and absolute configurations of the compounds 1, 3, and 4 were elucidated by NOESY and ECD. The biosynthesis pathways of these compounds were proposed, which involves in three key genes ChaA [polyketide synthase-non-ribosomal peptide synthetases (PKS-NRPS)], ChaB, and ChaC. Compounds 1-4 were tested for their antimicrobial activities, and compounds 2 and 3 showed moderate bioactivity against Staphylococcus aureus (SA) and methicillinresistant S. aureus (MRSA) with MIC values of 15.8 and 27.1 µM. The results showed that configuration of C-21 in 3 and 4 is important for anti-SA and anti-MRSA activities. This study reveals the significant potential of the genus Chaetomium in producing new PKS-NRPS, therefore increasing the speed in the mining for new sources of antimicrobial agents.

A pair of new quinolone alkaloid enantiomers, (Ra)-(-)-viridicatol (1) and (Sa)-(+)-viridicatol (4), along with seven known compounds 2, 3, and 5-9 were isolated from Penicillium christenseniae SD.84. The structure of 1and 4 ware determined by NMR and HRESIMS data. Compound 1 and 4 were determined to be a pair of enantiomers by theoretical calculation through CD and ECD. The MIC values of compound 4 against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus were 12.4 μM and 24.7 μM, compound 1 has no inhibitory activity. Antimicrobial assays of compounds 2, 3 and 5-7 showed moderate activity against methicillin-resistant Staphylococcus aureus and Staphylococcus aureus. This study reveals the significant potential of Penicillium sp. to produce new drug-resistant lead compounds, therefore increasing the speed in the mining for new sources of antimicrobial agents.

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