Fermentation conditions and antitumor products of an ocean-derived fungus Alternaria sp. 114-1G: a preliminary investigation / 国际药学研究杂志

ABSTRACT

Objective: To investigate and optimize the fermentation conditions of an ocean-derived fungus, Alternaria sp. 114- 1G, and isolate metabolites in the fermentation products to explore antitumor compounds in the products via the structure elucidation and in vitro antitumor activity assay. Another aim of this study is to accomplish a fundamental work for further research on new compounds from Alternaria sp. 114- 1G. Methods: The in vitro antitumor activity was assayed for the crude extracts and isolated compounds by the CCK-8 method using a human cervical cancer HeLa cell line. The fermentation conditions were investigated and opti- mized based on the biomass of the fermentation and the in vitro antitumor activity of crude extracts of the fermentation. For the separation and isolation of metabolites, the column chromatography was performed on silica gel and Sephadex LH-20 columns, and semi-preparative high performance liquid chromatography(semi-HPLC)was conducted on a COSMOSIL C18-MS-Ⅱ column(10 mm×250 mm). The obtained compounds were identified according to the MS, 1H NMR and13C NMR data. Results: The relatively favored fermentation conditions were as follows mannitol 25 g/L, maltose 15 g/L, glucose 10 g/L, monosodium glutamate 10 g/L, soybean peptone 5 g/L, yeast extract 3 g/L; 60% sea water in whole medium, initial pH 7.5; and fermentation at 10℃ for 15 days under a 150 r/min shaking speed on a rotary shaker. Four compounds 1-4 were isolated from the fermentation products of 114-1G strain and identified as cyclo (Gla-Tyr)(1), cyclo(Ala-Ile)(2), thymidine DNA nucleotide(3)and pachybasin(4). Among them, 4 showed a relatively stronger inhibitory activity on HeLa cells, with the 57.8% of inhibition rate at 100 μg/ml. Some other compounds were also isolated, and a phenolic one had been shown to be a new compound by a literature survey according to the planar structure deduced. Further studies on their structures were in progress. Conclusion: Fermentation conditions for Alternaira sp. 114-1G were investigated preliminarily, and four compounds 1-4 have been isolated from the fermentation products of the 114-1G strain. Among them, pachybasin(4)showed a relatively higher inhibitory effect on human cancer HeLa cells. Alternaira sp. 114-1G could produce new metabolites and the present study has provided a reliable groundwork for further research on new compounds from Alternaira sp. 114-1G.