Marine-derived fungi are a rich source of structurally diverse metabolites. Fungi produce an array of compounds when grown under different cultivation conditions. In the present work, different media were used to cultivate the fungus Aspergillus sp. ZA-01, which was previously studied for the production of bioactive compounds, and three new prenylxanthone derivatives, aspergixanthones I–K (1–3), and four known analogues (4–7) were obtained. The absolute configuration of 1 was assigned by ECD experiment and the Mo2(AcO)4 ICD spectrum of its methanolysis derivative (1a). All the compounds (1–7) were evaluated for their anti-Vibrio activities. Aspergixanthone I (1) showed the strongest anti-Vibrio activity against Vibrio parahemolyticus (MIC = 1.56 μM), Vibrio anguillarum (MIC = 1.56 μM), and Vibrio alginolyticus (MIC = 3.12 μM).

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Citrinin dimeric derivatives are bioactive polyketides previously reported from Penicillium, Aspergillus, and Monascus fungi species. Due to the large distance between the stereogenic centers of the two monomer units, it was difficult to determine the absolute configuration of the whole molecule (1). In previous work, the absolute configuration of 1 was just proposed by biogenetic considerations. To address this problem, the experimental VCD of 1 was compared with the corresponding DFT calculations for two diastereomers (1a and 1b). Also, the experimental ECD and NMR spectra of 1 were combined for analysis with the corresponding theoretical predictions for different diastereomers. Additionally, compound 1 showed promising anti-Vibrio activity against pathogenic Vibrio spp.with MIC values ranging from 0.4 to 0.8 μM.

In this paper, a simple high performance liquid chromatography (HPLC) method for the determination of colistimethate sodium in the productions of synthesis from colistin E sulphate was established. A HPLC gradient which was: 20% B+80% A changed to 50% B+50% A in 10 min (A was 0.05% TFA aqueous solution and B was acetonitrile) was used and the separation was realized in 8 minutes. Moreover, this method was also used in the separation of colistin sulphate with good resolution. Compared to the methods reported previously, the present method was finished easier in a much shorter time which is 6 min. LC-MS was used to detect colistin sulphate and the result showed that the two compositions were colistin sulphate E1 and E2 as expected. Good separation and reproducibility were obtained.

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