Two New 12-Membered Macrolides from Endophytic Fungi Cladosporium tenuissimum and Their Bioactivities

The chemical analysis of Cladosporium tenuissimum yielded six 12-membered macrolides (1-6), including 2 new ones (1 and 2) and 4 other compounds (7-10). Comprehensive spectroscopic techniques were employed to establish the structures, whereas electronic circular dichroism (ECD) calculations and Mosher's analysis were performed to confirm the absolute configurations of new compounds. We evaluated the metabolites for their cytotoxic activities, antifungal activity, and α-glucosidase. Notably, compound 1 exhibited moderate antifungal activity against Alternaria solani and Botrytis cinerea with minimum inhibitory concentration (MIC) values of 25 μM, respectively. Compounds 4 and 5 had the best inhibition against A. solani and B. cinerea, better than the positive control, hymexazol. Remarkably, compound 6 inhibited α-glucosidase with IC₅₀ value of 160 μM, outperforming acarbose by 12-fold. Enzyme reaction kinetics and molecular docking were used to investigate potential α-glucosidase inhibition mechanisms. Moreover, compound 7 exhibited moderate cytotoxicity against HeLa cells (IC₅₀ = 15.27 ± 0.72 μM), more active than etoposide. Consequently, the results provide a solid foundation for developing bioactive metabolites of C. tenuissimum.