Cerebrosides of the halotolerant fungus Alternaria raphani isolated from a sea salt field.

In order to search for structurally novel and bioactive natural compounds from marine-derived fungi, a halotolerant fungal strain (THW-18) identified as Alternaria raphani was isolated from sediment collected in the Hongdao sea salt field. From the ethyl acetate extract of Alternaria raphani, three new cerebrosides, alternarosides A-C (1-3), and a new diketopiperazine alkaloid, alternarosin A (4), together with 15 known compounds were isolated and identified by spectroscopic and chemical methods, as well as X-ray crystal diffraction analysis. Compounds 1-4 showed weak antibacterial activity against Escherichia coli, Bacillus subtilis, and Candida albicans with MIC values ranging from 70 to 400 muM.