College of Veterinary Medicine, Northwest A&F University, Yangling, 712100, Shaanxi, China.
Institute of Pratacultural Science, Tibet Academy of Agricultural and Animal Husbandry Sciences, Lhasa, 850000, Tibet, China.
BMC Microbiol. 2019 Feb 11;19(1):35. doi: 10.1186/s12866-019-1408-8.
The 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.
Alternaria 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.
In 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.
来源于内生真菌 Oxytropis alternata 的 indolizidine 生物碱 swainsonine 具有抗肿瘤、抗病毒和抑菌等多种生物活性。然而，Oxytropis alternata 产生的代谢产物的全部成分尚不清楚。本研究对 Oxytropis alternata 代谢产物进行了化学分析，不仅从发酵液中揭示了潜在的化合物，还研究了它们在哪些溶剂中被提取出来，从而促进了工业应用。
从甘肃棘豆中分离出的 Oxytropis alternata 菌株在 Czapek 培养基中培养 30 天以收集发酵液。发酵液用甲醇处理，然后蒸发至干，得到发酵液的浓缩物。浓缩物加水，然后用石油醚、氯仿、乙酸乙酯和正丁醇进行分步萃取。不同的提取物通过湿装和干装进行洗脱。得到的洗脱液通过 TLC 合并，以检测相同的馏分，然后通过 GC-MS 和 LC-MS 进行表征。GC-MS 结果表明，Oxytropis alternata 发酵液的石油醚、氯仿和乙酸乙酯相中有 105 种不同的化合物。此外，LC-MS 结果表明，Oxytropis alternata 发酵液中含有 5 种生物碱，即 2-羟基 indolizidine、retronecine、lentiginosine、swainsonine 和 swainsonine N-oxide。
除了 swainsonine 和 swainsonine N-oxide 外，还鉴定出 2-羟基 indolizidine、retronecine 和 lentiginosine 为 Oxytropis alternata 的次生代谢物。还检测到其他化合物，包括 5,6-二氢麦角甾醇、eburicol、羊毛甾醇和 L-苯丙氨酸-L-脯氨酸内酰胺，它们可能作为药物具有应用潜力。
