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化合物，使其成为探寻具备药理学与生物技术特性新型分子的极具潜力的类群。其中，微甘素（microginins）因作为血管紧张素转换酶抑制肽而受到关注，有望成为高血压与充血性心力衰竭治疗的潜在靶点。本研究建立了一种快速灵敏的方法，可通过液相色谱-三重四极杆串联质谱（LC-QqQ-MS/MS）对蓝细菌提取物中的微甘素进行非靶向筛查。这类化合物大多在N端含有3-氨基-2-羟基癸酸，该基团常可被氯化、二氯化或甲基化。基于该癸酸衍生物产生的碎片离子，本研究提出了前体离子扫描（precursor ion scan，PIS）策略。该方法在蓝细菌菌株与环境样本中识别出疑似微甘素，后经液相色谱-四极杆飞行时间串联质谱（LC-QTOF-MS/MS）验证。研究共检测到19种微甘素变体，并通过获得的碎片谱表征了其中8种新的微甘素结构。本研究证实了前体离子扫描模式采集用于非靶向筛查的适用性，可检测到主要由铜绿微囊藻（Microcystis aeruginosa）菌株产生的、带有氨基酸修饰的多种微甘素。该方法可作为识别与环境监测具备保守分子亚结构且碎裂模式相似的分子的有效工具。