海洋链霉菌Streptomyces sp. B9173合成的2-吲哚酮生物碱

【背景】海洋来源的天然产物近年来已成为小分子药物的重要来源。对海洋链霉菌Streptomyces sp. B9173的基因组分析显示,该菌包含多种天然产物的生物合成基因簇,具有产生多种新化合物的潜力。【目的】挖掘B9173菌株中未知的次级代谢产物,以期发现结构新颖或生物活性独特的化合物。【方法】利用HPLC/LC-MS结合的方法,排除了该菌株产生的已知化合物,确定3个未知化合物作为挖掘对象,然后利用正、反相硅胶柱色谱、葡聚糖凝胶柱色谱和高效液相色谱等技术对次级代谢产物进行分离纯化,最后得到化合物单体。利用质谱及核磁共振光谱技术对化合物结构进行解析和鉴定。【结果】确定3个化合物分别是色胺酮、甲基异靛蓝和N,N-二甲基异靛蓝,三者都属于2-吲哚酮生物碱。其中色胺酮具有非常广的生物活性,包括抗菌、抗肿瘤、抗炎症等,是药物开发的良好前体,这是首次在细菌中被分离得到。甲基异靛蓝是我国临床治疗慢性粒细胞白血病的药物,这是首次在微生物发酵液中被分离得到。目前这3个化合物均主要依赖化学合成。本研究结合B9173菌株的代谢背景,推测了3个化合物的生物合成途径。【结论】基于紫外吸收光谱和质谱特征,从B9173菌株的发酵液中分离鉴定了3个2-吲哚酮生物碱,丰富了微生物活性天然产物的种类,对3个化合物生物合成途径的推测也为进一步研究色胺酮和甲基异靛蓝的生物合成机制奠定基础,后续可利用合成生物学技术重构这类化合物的生物合成途径,提供更便捷、低成本的生物合成方法。

2-Oxindole alkaloids produced by marine-derived Streptomyces sp. B9173

Background] Marine-derived natural products have become an important source of small molecule drugs in recent years. Genomic analysis showed that Streptomyces sp. B9173 contains a variety of biosynthetic gene clusters of natural products, with the potential to generate multiple new compounds. Objective] The objective of this paper is to find new compounds with novel structures or unique biological activities from the strain B9173. Methods] With the method combined with HPLC and LC-MS, we excluded the known compounds produced by B9173 and identified three unknown compounds as isolation targets. The secondary metabolites were isolated and purified using normal or reverse phase column chromatography, gel column chromatography and high performance liquid chromatography (HPLC). The structures of the compounds were elucidated by using mass spectroscopy (MS) and nuclear magnetic resonance (NMR). Results] Three compounds were purified and identified as tryptanthrin, meisoindigo, and N,N-dimethylisoindigo. All three compounds belong to the 2-oxindole alkaloids. Tryptanthrin has diverse biological activity, including antibacterial activity, anti-inflammatory activity, anti-tumor activity. Tryptanthrin is a potential drug lead and it is the first time to be isolated from bacteria. Meisoindigo is a drug used for clinical treatment of chronic myelogenous leukemia in China. It was isolated for the first time in a microbial fermentation broth. Based on the metabolic background of B9173, we speculated the biosynthetic pathways of three compounds. Conclusion] Three 2-oxindole alkaloids were purified and structurally elucidated based on their UV-vis spectra and MS data. This study enriches the types of microbially active natural products. The proposed biosynthetic pathways will lay the foundation for further research on the biosynthetic mechanisms of tryptanthrin and meisoindigo. Subsequently biosynthetic pathways for this class of compounds can be reconstructed using synthetic biology techniques, which will provide more convenient and low-cost biosynthesis method for tryptanthrin and meisoindigo.