基于内共生的松节藻科若干关键海藻次生代谢的藻-菌互作研究

It was reported that as of 2012 more than 25 thousand marine-derived secondary metabolites, which usually possess new chemical structures and potent biological activities, have been discovered from marine organisms, and most of these metabolites were discovered based on the “solely study” on a single organisms. However, each of the organisms are not “solely exist” in the world and the production of these metabolites are affected not only by their own genetic properties, but also related to environmental factors as well as affected by the co-evolution with other organisms such as endo- and/or symbiotic microbes. During our previous investigation on some key species in the algal family Rhodomelaceae, a number of halogenated organic compounds were isolated and identified. Among them, the algal species in the genera Rhodomela, Polysiphonia, and Symphyocladia were found to mainly produce brominated phenolic metabolites, which usually containing 3-Br-4,5-dihydroxyphenyl-, 2,3-di Br-4,5-dihydroxyphenyl-, and 2,3,6-tri Br-4,5-dihydroxyphenyl- unit in these molecules, respectively, while the species from genus Laurencia could produce more diverse halomolecules. Based on these results, the current project will focus on the investigation of algae-endosymbiotic interactions on secondary metabolites of some key species of the algal family Rhodomelaceae. The aim of the project is to disclose the biodiversity of the endosymbiotic fungi of the Rhodomelaceae origin as well as their relation to the production of the algal-derived halogenated secondary metabolites. New halomolecules with interesting bioactivity will be discovered and new ideas on the study of natural products are expected to be developed.

截止2012年底科学家已从海洋生物中发现了2.5万余个结构新颖、活性显著的次生代谢产物。这些产物基本上都是基于对特定海洋生物的“孤立研究”获得的。实际上，自然界的任何生物都不是孤立存在的，其次生代谢产物的产生除受自身遗传特性的内因控制外，还与生态环境、与其他生物（共生/附生微生物）的协同进化等外部因素有关。我们前期研究发现，松节藻科若干关键海藻具有产生新结构卤代化合物的能力，其中多管藻属、松节藻属和鸭毛藻属海藻主要产生溴酚类化合物，且分子中分别含有3-溴-4,5-二羟基苯基、2，3-二溴-4,5-二羟基苯基和2，3，6-三溴-4,5-二羟基苯基单元（溴的取代度依次增加），而凹顶藻属海藻卤代化合物的分子多样性更加丰富。拟在前期研究基础上开展上述海藻次生代谢的藻-菌互作研究，获得其内生真菌的生物多样性与卤代化合物调控、产生的关系与规律，发现结构新颖的活性代谢产物，探讨海洋天然产物研究的新模式。

本项目按计划开展了松节藻科关键海藻卤代化合物及其内生真菌代谢产物研究，通过海藻内生真菌纯培养、藻-菌共培养、菌-菌共培养互作、优化，诱导海藻内生真菌产生分子多样性丰富的代谢产物。项目实施期间对松节藻科海藻的典型分布区域开展了资源调查与样品采集、海藻卤代化合物研究、内生真菌分离与鉴定、内生真菌培养优化、藻-菌共培养、菌-菌共培养优化、代谢产物分离与鉴定及生物活性评价等。从松节藻、冈村凹顶藻、羽枝凹顶藻等发现了结构新颖的卤代化合物、从优选的海藻内生真菌中经各种培养条件的优化，分离鉴定了结构新颖的代谢产物。项目执行期间共分离获得松节藻科海藻及其内生真菌代谢产物225个，其中国际上首次报道的新化合物39个，包括结构新颖的卤代化合物、萜类化合物、枝孢菌素类化合物、氧杂蒽酮类化合物等，若干化合物具有显著的抗肿瘤活性、抗菌（人类病原菌、水产病害菌和植物病害菌）活性、抗氧化/自由基清除活性和神经氨酸酶抑制活性等，具有潜在的应用前景。通过本项目研究可以发现，松节藻科海藻具有产生结构新颖的卤代化合物的能力，其内生真菌则能够产生分子多样性极其丰富的代谢产物，而通过菌-菌共培养和藻-菌互作共培养则可改变其代谢谱，产生结构类型不同的代谢产物。研究结果为海洋天然产物研究模式的探索提供了新的思路，为海藻及其内生真菌的利用提供了科学依据。..