The fungal strain, ZJ-M-5, was isolated from a mud sample collected on the coastal beach in Fenghua County, Zhejiang Province, China. The spores of ZJ-M-5 on PDA plates were inoculated into 150 mL of Czapek Dox broth without MgCl₂ in a 500 mL flask, and 77 flasks were incubated on a shaking platform at 28 ℃ for 7 days.

ZJ-M-5 produces different metabolites in the eutrophic and oligotrophic media, respectively. The difference in the sources of nitrogen and carbon might be the key. Sucrose acts as the sole carbon source and NaNO3 the sole inorganic nitrogen source in the Czapek Dox medium, while mannitol and glucose are the carbon sources in the eutrophic medium and yeast extract and peptone donate both carbon and nitrogen simultaneously. It can be conferred that the sole carbon source and the inorganic nitrogen source in Czapek Dox switched on the silent gene clusters encoding the enzymes necessary to the assembly of compound 4 and the three caryophyllene derivatives. The yield of xanthone 4 remained the same regardless of whether there was any Mg²⁺ in the Czapek Dox broth or not. Removal of Mg²⁺ from Czapek Dox stopped production of compound 3 but stimulated synthesis of compounds 1 and 2. The production of compounds 1-4 was inhibited by high concentrations of Mg²⁺ in the modified Czapek Dox broth.