G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch of the Russian Academy of Sciences, Vladivostok 690022, Russia.
Institute of Chemistry, Far Eastern Branch of the Russian Academy of Sciences, Vladivostok 690022, Russia.
Molecules. 2020 Oct 18;25(20):4778. doi: 10.3390/molecules25204778.
Echinochrome A (Ech A, ) is one of the main pigments of several sea urchin species and is registered in the Russian pharmacopeia as an active drug substance (Histochrome), used in the fields of cardiology and ophthalmology. In this study, Ech A degradation products formed during oxidation by O in air-equilibrated aqueous solutions were identified, isolated, and structurally characterized. An HPLC method coupled with diode-array detection (DAD) and mass spectrometry (MS) was developed and validated to monitor the Ech A degradation process and identify the appearing compounds. Five primary oxidation products were detected and their structures were proposed on the basis of high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) as 7-ethyl-2,2,3,3,5,7,8-heptahydroxy-2,3-dihydro-1,4-naphthoquinone (), 6-ethyl-5,7,8-trihydroxy-1,2,3,4-tetrahydronaphthalene-1,2,3,4-tetraone (), 2,3-epoxy-7-ethyl-2,3-dihydro-2,3,5,6,8-pentahydroxy-1,4-naphthoquinone (), 2,3,4,5,7-pentahydroxy-6-ethylinden-1-one (), and 2,2,4,5,7-pentahydroxy-6-ethylindane-1,3-dione (). Three novel oxidation products were isolated, and NMR and HR-ESI-MS methods were used to establish their structures as 4-ethyl-3,5,6-trihydroxy-2-oxalobenzoic acid (), 4-ethyl-2-formyl-3,5,6-trihydroxybenzoic acid (), and 4-ethyl-2,3,5-trihydroxybenzoic acid (). The known compound 3-ethyl-2,5-dihydroxy-1,4-benzoquinone () was isolated along with products -. Compound turned out to be unstable; its anhydro derivative was obtained in two crystal forms, the structure of which was elucidated using X-ray crystallography as 7-ethyl-5,6-dihydroxy-2,3-dioxo-2,3-dihydrobenzofuran-4-carboxylic acid and named echinolactone. The chemical mechanism of Ech A oxidative degradation is proposed. The in silico toxicity of Ech A and its degradation products and - were predicted using the ProTox-II webserver. The predicted median lethal dose (LD) value for product was 221 mg/kg, and, for products -, it appeared to be much lower (≥2000 mg/kg). For Ech A, the predicted toxicity and mutagenicity differed from our experimental data.
虾青素 A（Ech A）是几种海胆物种的主要色素之一，已在俄罗斯药典中注册为活性药物物质（Histochrome），用于心脏病学和眼科领域。在这项研究中，鉴定、分离和结构表征了在空气平衡水溶液中由 O 氧化形成的虾青素 A 降解产物。开发并验证了一种 HPLC 方法，结合二极管阵列检测（DAD）和质谱（MS），以监测虾青素 A 降解过程并鉴定出现的化合物。检测到五个主要的氧化产物，并根据高分辨率电喷雾电离质谱（HR-ESI-MS）提出了它们的结构，分别为 7-乙基-2,2,3,3,5,7,8-庚基-2,3,3,5,6,8-五羟基-2,3-二氢-1,4-萘醌（）、6-乙基-5,7,8-三羟基-1,2,3,4-四氢萘-1,2,3,4-四酮（）、2,3-环氧-7-乙基-2,3-二氢-2,3,5,6,8-五羟基-1,4-萘醌（）、2,3,4,5,7-五羟基-6-乙基茚-1-酮（）和 2,2,4,5,7-五羟基-6-乙基茚-1,3-二酮（）。分离出三种新型氧化产物，并使用 NMR 和 HR-ESI-MS 方法确定其结构为 4-乙基-3,5,6-三羟基-2-氧代苯甲酸（）、4-乙基-2-甲酰基-3,5,6-三羟基苯甲酸（）和 4-乙基-2,3,5-三羟基苯甲酸（）。还分离出了已知化合物 3-乙基-2,5-二羟基-1,4-苯醌（）以及产物-。化合物-不稳定，其脱水衍生物-以两种晶型获得，其结构通过 X 射线晶体学阐明为 7-乙基-5,6-二羟基-2,3-二氧代-2,3-二氢苯并呋喃-4-羧酸，并命名为虾青素内酯。提出了虾青素 A 氧化降解的化学机制。使用 ProTox-II 网络服务器预测了虾青素及其降解产物和-的体内毒性。产物的预测中位致死剂量（LD）值为 221mg/kg，而产物-的预测毒性要低得多（≥2000mg/kg）。对于虾青素 A，预测的毒性和致突变性与我们的实验数据不同。
