Microcystins (MCs) and nodularins (NODs) exhibit high structural variability, including modifications of the Adda (3S-amino-9S-methoxy-2S,6,8S-trimethyl-10-phenyldeca-4E,6E-dienoic acid) moiety. Variations include 9-O-desmethylAdda (DMAdda) and 9-O-acetylDMAdda (ADMAdda) which, unless targeted, may go undetected. Therefore, reference standards were prepared of [ADMAdda5]MCs and [DMAdda5]MCs, which were analyzed using multiple approaches. The cross-reactivities of the [DMAdda5]- and [ADMAdda5]MC standards were similar to that of MC-LR when analyzed with a protein phosphatase 2A (PP2A) inhibition assay, but were <0.25% when analyzed with an Adda enzyme-linked immunosorbent assay (ELISA). Oxidative cleavage experiments identified compounds that could be used in the analysis of total MCs/NODs in a similar fashion to the 2R-methyl-3S-methoxy-4-phenylbutanoic acid (MMPB) technique. Products from oxidative cleavage of both the 4,5- and 6,7-ene of Adda, DMAdda and ADMAdda were observed, and three oxidation products, one from each Adda variant, were chosen for analysis and applied to three field samples and a Nostoc culture. Results from the oxidative cleavage method for total Adda, DMAdda, and ADMAdda were similar to those from the Adda-ELISA, PP2A inhibition, and LC-MS/MS analyses, except for the Nostoc culture where the Adda-ELISA greatly underestimated microcystin levels. This oxidative cleavage method can be used for routine analysis of field samples and to assess the presence of the rarely reported, but toxic, DMAdda/ADMAdda-containing MCs and NODs.

中文翻译：

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通过氧化裂解 ADMAdda、DMAdda 和 Adda 部分来分析总微囊藻毒素和节球藻毒素

微囊藻毒素 (MC) 和节球藻毒素 (NOD) 表现出高度的结构变异性，包括 Adda（3S-amino-9S-methoxy-2S,6,8S-trimethyl-10-phenyldeca-4E,6E-dienoic acid）部分的修饰。变异包括 9-O-desmethylAdda (DMAdda) 和 9-O-acetylDMAdda (ADMAdda)，除非有针对性，否则可能无法检测到。因此，制备了 [ADMAdda5] MC 和 [DMAdda5] MC 的参考标准，并使用多种方法对其进行了分析。[DMAdda5]- 和 [ADMAdda5]MC 标准品的交叉反应性在使用蛋白磷酸酶 2A (PP2A) 抑制测定法分析时与 MC-LR 相似，但在使用 Adda 酶联法分析时小于 0.25%免疫吸附试验（ELISA）。氧化裂解实验确定了可用于以与 2R-甲基-3S-甲氧基-4-苯基丁酸 (MMPB) 技术类似的方式分析总 MC/NOD 的化合物。观察到 Adda、DMAdda 和 ADMAdda 的 4,5- 和 6,7-ene 的氧化裂解产物，选择三种氧化产物（每个 Adda 变体各一种）进行分析并应用于三个现场样品和一个 Nostoc文化。总 Adda、DMAdda 和 ADMAdda 的氧化裂解方法的结果与 Adda-ELISA、PP2A 抑制和 LC-MS/MS 分析的结果相似，除了在 Nostoc 培养物中 Adda-ELISA 大大低估了微囊藻毒素水平。这种氧化裂解方法可用于现场样品的常规分析，并评估很少报道但有毒的物质的存在，