Six new epipolythiodioxopiperazine (ETP) alkaloids, penicisulfuranols A–F (1–6), were isolated from the mangrove endophytic fungus Penicillium janthinellum HDN13-309. All structures including absolute configurations were elucidated on the basis of comprehensive spectroscopic data and ECD calculations. They belong to the unusual family of ETPs containing sulfur atoms on both α- and β-positions of amino acid residues and a rare 1,2-oxazadecaline core moiety. In addition, compounds 1–6 also possess a rare spiro-furan ring and 1–3 showed cytotoxicity with IC50 values ranging from 0.1 to 3.9 μM.

S-Bridged pyranonaphthoquinone dimers, naquihexcins A and B (1 and 2), together with a related analogue (−)-BE-52440A (3) were obtained from the culture of a sponge-derived Streptomyces sp. HDN-10-293. Naquihexcin A (1) bears a rare unsaturated hexuronic acid moiety, and (−)-BE-52440A (3) has been discovered from natural resources. Compound 3 showed cytotoxicity against NB4 and HL-60 cells, while 1 could inhibit the proliferation of the adriamycin resistant human breast cancer cell line MCF-7 ADM.

Six new pyridone alkaloids, named penipyridones A–F (1–6), were isolated from the fermentation broth of an Antarctic moss-derived fungus, Penicillium funiculosum GWT2-24. Their structures were elucidated from extensive NMR and MS data. Although they possess the same major chromophore and some of them presented almost mirror ECD spectra, their absolute configurations were found to be uniformly S, as evidenced by X-ray single-crystal diffraction analysis, stereocontrolled total synthesis, and chemical conversions. TDDFT-ECD calculations of compounds 3 and 6 revealed that subtle conformational changes are responsible for the significantly different ECD curves. None of the compounds were cytotoxic (IC50 > 50 μM), while compounds 1, 2, 5, and 7 elicited lipid-lowering activity in HepG2 hepatocytes.

Since the discovery of penicillin, fungi have been an important source of bioactive natural products. However, as a specific resource, the bioactive potentiality and specificity of fungal metabolites from the Antarctic region have had little attention. In this paper, we investigated the diversity patterns and biological activities of cultivable fungi isolated from soil samples in Fildes Peninsula, King George Island, Antarctica. Fungal communities showed low abundance and diversity; a total of 150 cultivable fungi were isolated from eight soil samples. After being dereplicated by morphological characteristics and chemical fingerprints, 47 fungal isolates were identified by ITS-rDNA sequencing. We confirmed that these isolates belonged to at least 11 different genera and clustered into nine groups corresponding to taxonomic orders in the phylogenetic analysis. Using two different fermentation conditions, 94 crude extracts acquired from the abovementioned different metabolite characteristic isolates were screened by bioactivity assay and 18 isolates produced biologically active compounds. Compared with HPLC–DAD–UV fingerprint analysis of culture extracts and standard compounds, two bioactive components secalonic acid and chetracins were identified. Our research suggests that the abundance and diversity of Antarctic cultivable fungal communities exhibit unique ecological characteristics and potential producers of novel natural bioactive products.

Two new meroterpenoids, named chrodrimanins I and J (1 and 2), together with five known biosynthetically related chrodrimanins (3–7), were isolated from the culture of the Antarctic moss-derived fungus Penicillium funiculosum GWT2-24. Distinguished from all of the reported chrodrimanins, compounds 1 and 2 possess a unique cyclohexanone (E ring) instead of a δ-lactone ring. These structures including the absolute configurations were established on the basis of MS, NMR, and X-ray crystallographic analysis. Compounds 1–7 showed no cytotoxic or antibacterial activities, while the known compounds 3, 5, and 6 exhibited inhibitory activities against influenza virus A (H1N1), with IC50 values ranged from 21 to 57 μM.

Genome scanning of the reed rhizosphere soil-derived Streptomyces sp. CHQ-64 revealed a partial gene cluster, putatively encoding a polyene-polyol compound. Inspired by this finding, six new polyene-polyol macrolides, reedsmycins A–F (1–6), were isolated guided by the characteristic NMR signals. Their structures were elucidated using mass spectrometry and extensive NMR spectroscopy. Among them, reedsmycin F (6) possessed a rare 31-membered macroring containing a tetrahydrofuran motif, and reedsmycin A (1) exhibited promising activity against Candida albicans with a MIC of 25–50 μM, in a comparable level to that of the positive control nystatin.

Spicarins A (1) and B (2), two novel isobenzfuran-aspochalasin heterodimers, and spicarins C (3) and D (4), two isobenzofuran dimers, were isolated from the acetylated products of the marine-derived fungus Spicaria elegans KLA03. The structures of compounds 1–4 were elucidated by spectroscopic and/or X-ray diffraction methods. Compounds 3 and 4 inhibited lipopolysaccharide (LPS)-induced nitric oxide production in BV2 microglial cells.

Two new meroterpenes, phenylpyropenes E (1) and F (2), together with seven known phenylpyropenes (3–5) and pyripyropenes (6–9) were isolated from the marine-derived fungus Penicillium concentricum ZLQ-69. Their structures including the absolute configurations were elucidated using a combination of spectroscopic methods and electronic circular dichroism calculation. Bioactivity evaluation showed that compounds 1 and 4 were cytotoxic to the MGC-803 cell line with IC50 values of 19.1 and 13.6 μM, respectively.

Four new cyclic peptides, psychrophilins E–H (1–4), possessing a rare amide linkage between the carboxylic acid in anthranilic acid (ATA) and the nitrogen from an indole moiety, along with a new ATA-containing hexapeptide, versicotide C (5), were obtained from the culture of the marine-derived fungus Aspergillus versicolor ZLN-60. The structures, including absolute configurations, were elucidated by a combination of HRESIMS, NMR, X-ray crystallography, TDDFT ECD calculations, and Marfey’s method. Versicotide C (5) is the first natural cyclic hexapeptide containing two anthranilic acids. Compounds 1–5 were not cytotoxic, and compound 3 showed potent lipid-lowering effects.

Two new epipolythiodioxopiperazines, named chetracins B and C (1 and 2), and five new diketopiperazines, named chetracin D (4) and oidioperazines A–D (5, 10, 12, and 13), were isolated from the fungus Oidiodendron truncatum GW3-13, along with six known compounds (3, 6, 7, 8, 9, and 11). Their structures were elucidated by extensive NMR, MS, and CD analyses, as well as chemical transformation. An in vitro MTT cytotoxicity assay revealed potent biological activity for 1 in the nanomolar range against a panel of five human cancer lines.

A new pyronepolyene C-glucoside, named iso-D8646-2-6 (1) together with the known related compound D8646-2-6 (2), was isolated from the sponge-associated fungus Epicoccum sp. JJY40. They showed NF-κB inhibitory and anti-influenza A viral (H1N1) activities.

A novel actinomycete strain, GW25-5T, was isolated from a soil sample collected from the Fildes Peninsula, King George Island, West Antarctica. The strain was characterized by white to grey aerial mycelia, which were differentiated to straight to flexuous spore chains, with rod-shaped smooth spores. The cell wall of strain GW25-5T contained LL-diaminopimelic acid (A2pm) and traces of meso-A2pm. Whole-cell sugars were galactose and minor amounts of mannose and glucose. The predominant menaquinones were MK-9(H6) (49%), MK-9(H8) (24%) and MK-9(H4) (12%). The phospholipids contained DPG, PE, PI, PIM and PL(s). The major cellular fatty acids were iso-C16:0 and anteiso-C15:0. Genomic DNA G+C content of strain GW25-5T was 70.0 mol%. BLAST result showed that strain GW25-5 has the 16S rRNA gene sequence highest similarity of 97.5% with members of genus Streptomyces and phylogenetic analysis indicated that this strain belongs to the genus Streptomyces. DNA–DNA relatedness values of strain GW25-5T with the closest species of Streptomycespurpureus LMG 19368T and Streptomycesbeijiangensis YIM 6T were significantly lower than 70% of the threshold value for the delineation of genomic species. A polyphasic taxonomic investigation based on a judicious combination of genotypic and phenotypic characteristics revealed that the organism represents a novel species of the genus Streptomyces. Thus, we propose strain GW25-5T as the type strain of this novel species, Streptomycesfildesensis (=CGMCC 4.5735T = YIM 93602T = DSM 41987T = NRRL B 24828T).