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Updated: May 28, 2026

Functionalized Spirocyclic Heterocycle Synthesis and Cytotoxicity Assay
Published on: February 9, 2021
Cytotoxic Synurins A-C: Chlorinated Naphthoquinone Pigments from the Freshwater Alga Synura sphagnicola
Magda Škaloudová1, Jan Blahut2, Jan Hájek3
1Faculty of Science, Charles University, Prague 128 43, Czech Republic.
Abstract:
Synura sphagnicola, a peat bog chrysophyte, forms conspicuous red cytoplasmic droplets. These droplets previously showed an unidentified pigment, prompting a detailed chemical investigation. Large-scale cultivation and chromatographic purification yielded three structurally related orange-to-red compounds, previously undescribed chlorinated naphthoquinone pigments─synurin A (1), synurin B (2), and synurin C (3)─whose identities were established using HPLC-HRMS, FT-ICR MS, NMR spectroscopy, FTIR, fluorescence spectroscopy, and Raman microscopy. The compounds were identified as 2,3-dichloro-5,8-dihydroxy-6-propylnaphthalene-1,4-dione (1) and its two O-methylated regioisomers (2, 3). Raman spectra revealed strong environment-dependent vibrational differences, particularly for 1 and 2. In vitro assays demonstrated potent but nonselective cytotoxicity toward cancerous and nontransformed cell lines (IC50 in the low micromolar range), while only 1 exhibited ferric-reducing antioxidant activity.
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