Cyclo-(TRP-PHE) diketopiperazines from the endophytic fungus Aspergillus versicolor isolated from Piper aduncum

Isolation, Structural Characterization and Antidiabetic Activity of New Diketopiperazine Alkaloids from Mangrove Endophytic Fungus Aspergillus sp. 16-5c

Six new DIKETOPIPERAZINE alkaloids aspergiamides A-F (1-6), together with ten known alkaloids (7-16), were isolated from the mangrove endophytic fungus Aspergillus sp. 16-5c. The structures of the new compounds were elucidated based on 1D/2D NMR spectroscopic and HR-ESIMS data analyses. The absolute configurations of aspergiamides A-F were established based on the experimental and calculated ECD data. All the compounds were evaluated for the antidiabetic activity against α-glucosidase and PTP1B enzyme. The bioassay results disclosed compounds 1 and 9 exhibited significant α-glucosidase inhibitory with IC₅₀ values of 18.2 and 7.6 μM, respectively; compounds 3, 10, 11, and 15 exhibited moderate α-glucosidase inhibition with IC₅₀ values ranging from 40.7 to 83.9 μM; while no compounds showed obvious PTP1B enzyme inhibition activity.

New Prenylated Indole Homodimeric and Pteridine Alkaloids from the Marine-Derived Fungus Aspergillus austroafricanus Y32-2

Chemical investigation of secondary metabolites from the marine-derived fungus Aspergillus austroafricanus Y32-2 resulted in the isolation of two new prenylated indole alkaloid homodimers, di-6-hydroxydeoxybrevianamide E (1) and dinotoamide J (2), one new pteridine alkaloid asperpteridinate A (3), with eleven known compounds (4-14). Their structures were elucidated by various spectroscopic methods including HRESIMS and NMR, while their absolute configurations were determined by ECD calculations. Each compound was evaluated for pro-angiogenic, anti-inflammatory effects in zebrafish models and cytotoxicity for HepG2 human liver carcinoma cells. As a result, compounds 2, 4, 5, 7, 10 exhibited pro-angiogenic activity in a PTK787-induced vascular injury zebrafish model in a dose-dependent manner, compounds 7, 8, 10, 11 displayed anti-inflammatory activity in a CuSO₄-induced zebrafish inflammation model, and compound 6 showed significant cytotoxicity against HepG2 cells with an IC₅₀ value of 30 µg/mL.