Two New Epimeric Decalinoylspirotetramic Acid Derivatives From the <i>Acanthus ilicifolius</i> ‐Derived Fungus <i>Trichoderma</i> sp. RSF‐1

Two new epimeric decalinoylspirotetramic acid derivatives, trichodecalins A and B (1 and 2), together with six known compounds (3-8), were isolated from the fungus Trichoderma sp. RSF-1, which is derived from the mangrove Acanthus ilicifolius. Their structures, including absolute configurations, were established using extensive spectroscopic methods (1D and 2D NMR, IR, HR-ESI-MS, ECD). Notably, compounds 1 and 2 were identified as new members of the decalinoylspirotetramic acid family. The cytotoxic and antibacterial activities of these compounds were evaluated. Compounds 1, 2 and four known compounds showed antibacterial activities against multiple pathogenic bacteria. Specifically, compound 2 exhibited strong inhibitory activity against Bacillus subtilis ATCC 19659 with a minimum inhibitory concentration (MIC) value of 6.25 µg/mL, whereas compounds 1 and 2 showed moderate inhibitory activities against Escherichia coli ATCC 25922 and Pseudomonas fulva ZXM181.