Structurally specialised metabolites with antimicrobial and enzyme inhibitory activities from Hadal Trench-derived Nigrocephalum sp. SCSIO41049.

Two undescribed triterpene glycosides (1-2), one undescribed sesquiterpene glycoside (3), three undescribed α-pyrone derivatives (4-6) and one undescribed aliphatic hydrocarbon (7), along with twelve known compounds (8-19), were obtained from a culture of the fungus Nigrocephalum sp. SCSIO41049, separated from Mariana Trench sediment. Compounds 1 and 2 were the first discovered lanostane-type triterpenes with a d-mannose attached at the C-23. Compound 14 was isolated from nature for the first time. Their structures were elucidated based on 1D, 2D NMR and HR-ESI-MS spectral data analysis, followed by electronic circular dichroism (ECD) calculations, single-crystal X-ray diffraction analysis and acid hydrolysis reaction. All compounds were tested for their antimicrobial, enzyme inhibition and antitumor effects. Compound 1 displayed the potent inhibitory effect on Fusarium oxysporum HNM1003 with MIC value of 4 μg/mL. Compounds 6, 8, 11 and 15 demonstrated moderate inhibitory effects on Curvularia australiensis. Compounds 1, 2 and 10 exhibited significant neuraminidase inhibitory activity with IC50 values ranging from 33.02 to 43.55 μM.