MICROGININS SCREENING IN CYANOBACTERIA BY LC-MS

Cyanobacteria produce a wide variety of bioactive compounds, making them a highly promising group in the search for novel molecules with pharmacological and biotechnological properties. Among these, microginins attract attention for being peptides which inhibit angiotensin-converting enzyme, turning them into potential targets for hypertension and congestive heart failure treatment. This work describes a rapid and sensitive method for untarget screening of microginins in cyanobacteria extracts by LC-QqQ-MS/MS. These compounds are mostly characterized by containing 3-amino-2-hydroxy-decanoic acid at the N-terminus, which often could be chlorinated, dichlorinated or methylated. Based on the fragment ion arising from this decanoic acid derivative, a precursor ion scan (PIS) strategy has been proposed. This approach identified suspect microginins in cyanobacterial strains and environmental samples that were later confirmed by LC-QTOF-MS/MS. Eight new microginins structures were characterized based on the obtained fragmentation spectra from a total of 19 variants detected. This study highlights the applicability of PIS mode acquisition for untarget screening, detecting a wide variety of microginins with amino acids modifications, produced mainly by Microcystis aeruginosa strains. This method is a useful tool for the identification and environmental monitoring of molecules with conserved molecular substructures that possess similar fragmentation pattern蓝细菌（Cyanobacteria）可产生种类繁多的生物活性物质，使其成为筛选具有药理学及生物技术特性新型分子的极具潜力的类群。其中，微甘素（microginins）作为可抑制血管紧张素转换酶的肽类物质而受到关注，使其成为高血压与充血性心力衰竭治疗的潜在靶点。本研究建立了一种基于LC-QqQ-MS/MS（液相色谱-三重四极杆串联质谱）的快速灵敏方法，用于蓝细菌提取物中微甘素的非靶向筛查。这类化合物的主要结构特征为N端含有3-氨基-2-羟基癸酸，该基团常可发生氯化、二氯化或甲基化修饰。基于该癸酸衍生物产生的特征碎片离子，本研究提出了前体离子扫描（Precursor Ion Scan, PIS）策略。该策略可在蓝细菌菌株与环境样本中筛查到疑似微甘素，后续通过LC-QTOF-MS/MS（液相色谱-四极杆飞行时间串联质谱）完成验证。基于检测到的19种微甘素变体的碎裂光谱，本研究解析了8种全新的微甘素结构。本研究证实了前体离子扫描模式用于非靶向筛查的适用性，成功检测到多种经氨基酸修饰的微甘素，这些物质主要由铜绿微囊藻（Microcystis aeruginosa）菌株产生。该方法可作为一类具有保守分子亚结构且碎裂模式相似的分子的鉴定与环境监测的有效工具。