Two new secondary metabolites from a mangrove-derived fungus Cladosporium sp. JS1-2

One new pentenoic acid derivative, named 1,1'-dioxine-2,2'-dipropionic acid (1) and a new natural product, named 2-methylacetate-3,5,6-trimethylpyrazine (2), along with six known compounds (3-8), were obtained from the Cladosporium sp. JS1-2, an endophytic fungus isolated from the mangrove Ceriops tagal collected in South China Sea. Their structures were elucidated by detailed analysis of comprehensive spectroscopic data, and the structure of 1 was further determined by X-ray diffraction analyses. ¹³C NMR chemical shifts of structure 2 was further determined by GIAO based ¹³C NMR chemical shifts calculations. Compounds 1-4 and 6 showed growth inhibition activities against newly hatched larvae of Helicoverpa armigera Hubner with the IC₅₀ values ranging from 100 to 150 μg ml^-1. Compounds 1, 2, 4, 6 and 7 showed moderate antibacterial activities against Staphylococcus aureus with the MIC values of 25.0, 12.5, 6.25, 1.25, and 6.25 μg ml^-1, respectively.