Abstract
BackgroundThe indolizidine alkaloid-swainsonine is produced by an endophytic fungus Alternaria oxytropis, which was isolated from locoweeds. Swainsonine has many biological activities such as anti-tumorigenic, anti-viral and bacteriostatic. However, the full complement of metabolites produced by Alternaria oxytropis is not known. This study is a chemical analysis of Alternaria oxytropis metabolites, which not only unravels the potential compounds from the fermentation broth but also in which solvent are they extracted, facilitating industrial application.ResultsAlternaria oxytropis isolated from Oxytropis gansuensis was cultured in Czapek’s medium for 30d to collect the fermentation broth. The fermentation broth is treated with methanol and then evaporated to dryness to obtain a concentrate of the fermentation broth. The concentrate is added with water for the subsequent fractional extraction with petroleum ether, chloroform, ethyl acetate and n-butanol. Different fractions of the extract were eluted by wet packing and dry loading. The obtained eluate was combined by TLC to detect the same fraction, and then characterized by GC-MS and LC-MS. The results of GC-MS showed that 105 different compounds existed in the petroleum ether, chloroform, and ethyl acetate phases of Alternaria oxytropis fermentation broth. Moreover, the results of LC-MS indicated that the fermentation broth of Alternaria oxytropis contained five alkaloids, 2-hydroxy-indolizidine, retronecine, lentiginosine, swainsonine and swainsonine N-oxide.ConclusionsIn addition to swainsonine and swainsonine N-oxide, 2-hydroxy-indolizidine, retronecine and lentiginosine were identified as the secondary metabolites of Alternaria oxytropis. Other compounds were also detected including 5,6-dihydroergosterol, eburicol, lanosterol, and L-phenylalanyl-L-proline lactam, which have potential applications as drugs.
Highlights
The indolizidine alkaloid-swainsonine is produced by an endophytic fungus Alternaria oxytropis, which was isolated from locoweeds
Fractional extraction of the broth followed by chemical analysis of the solvents To detect the relatively small polar and volatile substances in the metabolites of Alternaria oxytropis, we analyzed the petroleum ether phase, chloroform phase, and ethyl acetate phase by GC-MS
We dispersed concentrates of the metabolites of Alternaria oxytropis by adding water, and extracted it with petroleum ether according to the polarity of the extractant from low to high
Summary
The indolizidine alkaloid-swainsonine is produced by an endophytic fungus Alternaria oxytropis, which was isolated from locoweeds. The full complement of metabolites produced by Alternaria oxytropis is not known. This study is a chemical analysis of Alternaria oxytropis metabolites, which unravels the potential compounds from the fermentation broth and in which solvent are they extracted, facilitating industrial application. Swainsonine can cause neurological symptoms and pathological changes to animals that consume locoweeds. Swainsonine is a water-soluble indolizidine alkaloid, which was originally extracted from Swainsona canescens [10]. In 1982, Molyneux et al isolated swainsonine. You et al [22] found that swainsonine can directly inhibit the growth of liver cancer cells and enhance the response of liver cancer cells to paclitaxel. Scott et al showed that the susceptibility of apolipoprotein E knockout mice to cardiovascular disease is related to the sensitivity of mice to immunomodulatory effects of swainsonine [27]
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