Three new isocoumarins—dichlorodiaportintone (1), desmethyldichlorodiaportintone (2) and desmethyldichlorodiaportinol (3)—as well as six known analogues (4–9) were isolated from the culture of the mangrove endophytic fungus Ascomycota sp. CYSK-4 from Pluchea indica. Their structures were elucidated by analysis of spectroscopic data. The absolute configuration of compounds 1 and 2 were determined by the modified Mosher’s method. Compound 2 showed significant anti-inflammatory activity by inhibiting the production of NO in LPS-induced RAW 264.7 cells with IC₅₀ value of 15.8 μM, while compounds 1, 5, and 6 exhibited weak activities with IC₅₀ values of 41.5, 33.6, and 67.2 μM, respectively. In addition, compounds 1, 5, and 6 showed antibacterial effects against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Klebsiella pneumoniae, and Acinetobacter calcoaceticus with the MIC values in the range of 25–50 μg·mL⁻¹.

Four new polyketides: nectriacids A–C (1–3) and 12-epicitreoisocoumarinol (4), together with three known compounds: citreoisocoumarinol (5), citreoisocoumarin (6), and macrocarpon C (7) were isolated from the culture of the endophytic fungus Nectria sp. HN001, which was isolated from a fresh branch of the mangrove plant Sonneratia ovata collected from the South China Sea. Their structures were determined by the detailed analysis of NMR and mass spectroscopic data. The absolute configuration of the stereogenic carbons for compound 4 was further assigned by Mosher’s ester method. All of the isolated compounds were tested for their α-glucosidase inhibitory activity by UV absorbance at 405 nm, and new compounds 2 and 3 exhibited potent inhibitory activity with IC₅₀ values of 23.5 and 42.3 μM, respectively, which were more potent than positive control (acarbose, IC₅₀, 815.3 μM).

Two new sulfur-containing benzofuran derivatives, eurothiocin A and B (1 and 2), along with five known compounds, zinniol (3), butyrolactone I (4), aspernolide D (5), vermistatin (6), and methoxyvermistatin (7), were isolated from the cultures of Eurotium rubrum SH-823, a fungus obtained from a Sarcophyton sp. soft coral collected from the South China Sea. The new compounds (1 and 2) share a methyl thiolester moiety, which is quite rare among natural secondary metabolites. The structures of these metabolites were assigned on the basis of detailed spectroscopic analysis. The absolute configurations of 1 and 2 were determined by comparison of the experimental and calculated electronic circular dichroism (ECD) data. Compounds 1 and 2 exhibited more potent inhibitory effects against α-glucosidase activity than the clinical α-glucosidase inhibitor acarbose. Further mechanistic analysis showed that both of them exhibited competitive inhibition characteristics.

Chemical investigation of the endophytic fungus Aspergillus sp. 16-5B cultured on Czapek’s medium led to the isolation of four new metabolites, aspergifuranone (1), isocoumarin derivatives (±) 2 and (±) 3, and (R)-3-demethylpurpurester A (4), together with the known purpurester B (5) and pestaphthalides A (6). Their structures were determined by analysis of 1D and 2D NMR spectroscopic data. The absolute configuration of Compound 1 was determined by comparison of the experimental and calculated electronic circular dichroism (ECD) spectra, and that of Compound 4 was revealed by comparing its optical rotation data and CD with those of the literature. The structure of Compound 6 was further confirmed by single-crystal X-ray diffraction experiment using CuKα radiation. All isolated compounds were evaluated for their α-glucosidase inhibitory activities, and Compound 1 showed significant inhibitory activity with IC₅₀ value of 9.05 ± 0.60 μM. Kinetic analysis showed that Compound 1 was a noncompetitive inhibitor of α-glucosidase. Compounds 2 and 6 exhibited moderate inhibitory activities.

Two new diphenyl ethers (1 and 2) and four new phenolic bisabolane sesquiterpenoids (3–6), together with five known related derivatives, were isolated from the culture of the endophytic fungus Aspergillus flavus QQSG-3 obtained from a fresh branch of Kandelia obobata, which was collected from Huizhou city in the province of Guangdong, China. The structures of compounds 1–6 were determined by analyzing NMR and HRESIMS data. The absolute configurations of 5 and 6 were assigned by comparing their experimental ECD spectra with those reported for similar compounds in the literature. All isolates were evaluated for their α-glucosidase inhibitory activity, of which compounds 3, 5, 10, and 11 showed strong inhibitory effects with IC₅₀ values in the range of 1.5–4.5 μM.

Four phenylfuropyridone racemates, (±)-tersones A-C and E (1–3, 5), one phenylpyridone racemate, (±)-tersone D (4), one new pyridine alkaloid, tersone F (6), single new phenylfuropyridone, tersone G (7) and two known analogs 8 and 9 were isolated from the deep-sea fungus Phomopsis tersa. Their structures and absolute configurations were characterized on the basis of comprehensive spectroscopic analyses, single-crystal X-ray diffraction experiments, and electronic circular dichroism (ECD) calculations. Moreover, compounds 1–9 were evaluated for in vitro antimicrobial and cytotoxic activity. Compounds 5b and 8b exhibited antibacterial activity against S. aureus with the MIC value of 31.5 μg/mL, while compound 5b showed cytoxic activities against SF-268, MCF-7, HepG-2 and A549 cell lines with IC₅₀ values of 32.0, 29.5, 39.5 and 33.2 μM, respectively.