Simultaneous Measurement of Fluoroquinolones in Eggs by a Combination of Supercritical Fluid Extraction and High Pressure Liquid Chromatography

Simultaneous detection of the fluoroquinolone antibiotics ciprofloxacin, enrofloxacin, ofloxacin, and norfloxacin in eggs by a combination of supercritical fluid extraction (SFE) and high pressure liquid chromatography (HPLC) was studied. Lipid matrices that have been considered to result in poor extraction and isolation of fluoroquinolones in eggs were removed first by SFE with supercritical CO₂ alone, and then the fluoroquinolones were extracted by SFE with supercritical CO₂ containing 20% (v/v) methanol for HPLC analysis. A time-course study of the extraction of lipid matrices of eggs suggested that the SFE method successfully removed the matrices within 20 min. When the fluoroquinolones added to control eggs were extracted by SFE, the extraction efficiency was similar to that by the solvent extraction method, giving the recovery percentages from 83 to 96% in a 40 min-extraction time. The fluoroquinolones extracted from eggs by SFE were analyzed simultaneously by HPLC equipped with a fluorescence detector with detection sensitivity at about 10 ppb for the detection limit. The standard calibration profiles of fluoroquinolones showed linear responses to HPLC, showing more than 0.995 for the mean r ² value. This is the first report of the simultaneous measurement of fluoroquinolones in eggs by a combination of SFE and HPLC. Using the SFE method allowed us to avoid extensive sample preparation such as solvent extraction and chromatographic cleanup that are basically required in extraction of fluoroquinolones.     

A preparative method for isolation of fucoxanthin from Eisenia bicyclis by centrifugal partition chromatography

Introduction – Eisenia bicyclis (Kjellman) Setchell (Laminariaceae) is a common brown alga that inhabits around the coast of Korea, Japan and China. It contains fucoxanthin, a major carotenoid of brown algae which shows a variety of pharmaceutical functions. Objective – The aim of this investigation was the quantification and preparative isolation of fucoxanthin from fresh E. bicyclis using a new separation scheme, centrifugal partition chromatography (CPC). Methodology – The fucoxanthin fraction (Fuco fraction) was prepared by solvent partition method from the acetone extract of fresh E. bicyclis. Fuco fraction was used for CPC using a two‐phase solvent system of n‐hexane–ethyl acetate–ethanol–water (5:5:7:3, v/v/v/v). The flow rate of mobile phase was 2 mL/min with descending mode while rotating at 1000 rpm. The eluate was monitored at 410 nm. The content and structure of fucoxanthin in the CPC fraction were confirmed with HPLC, UV, APCI/MS and NMR spectra. Results – A preparative CPC yielded 20 mg of fucoxanthin (87% recovery from Fuco fraction) in a two‐step separation from 516 mg of Fuco fraction containing 4.59% fucoxanthin. The purity of the isolated fucoxanthin was about 81% in the first CPC step and over 98% in the second CPC step based on the calibration curve. The isolated fucoxanthin was identified as all‐trans‐fucoxanthin with APCI/MS (parent ion at m/z 641 [M + H ? H₂O]⁺) and ¹H, ¹³C and 2‐D NMR spectra. Conclusion – High‐purity fucoxanthin was successfully isolated from fresh E. bicyclis, suggesting further potential applications in the industrial use of this valuable carotenoid. Copyright © 2011 John Wiley & Sons, Ltd.     

Preparative separation of the saponin lancemaside a from Codonopsis lanceolata by centrifugal partition chromatography

Introduction. Lancemaside A is a saponin that inhibits decreases in blood testosterone level and thus prevents or ameliorates symptoms associated with male climacteric disorder. Our initial attempt to preparative isolation of lancemaside A from the saponin fraction of Codonopsis lanceolata roots by a preparative HPLC did not give a clear result. Objective. To develop a simple and efficient method for the preparative isolation of lancemaside A from the hot water extract of C. lanceolata roots using centrifugal partition chromatography (CPC). Methodology. The saponin fraction obtained from the hot water extract of C. lanceolata roots was used as the sample for preparative‐scale separation of lancemasides by CPC using n‐hexane:n‐butanol:methanol:0.1% aqueous formic acid (3:4:1:6, v/v) as the two‐phase solvent system. The upper phase (organic phase) of the two‐phase solvent system was used as the mobile phase, and 0.5 g of saponin fraction was applied for separation by CPC. Each fraction that was separated by CPC was analysed by HPLC, and the fractions containing each of the separated compounds were pooled together, and then were purified by simple preparative HPLC. Results. The demonstrated separation sequence, hot water extraction, DIAION HP‐20 column chromatography, CPC and preparative HPLC, yielded lancemaside A, foetidissimoside A and astersaponin Hb in their pure forms. Conclusion. The simple and efficient method for the preparative isolation of lancemaside A along with two other saponins, foetidissimoside A and astersaponin Hb, from the saponin fraction of C. lanceolata was established using CPC.     

Fractionation of UV-B absorbing molecules and of free radical scavenging compounds from Solieria chordalis by using centrifugal partition chromatography

Liquid-liquid chromatography can lead to the isolation of compounds or enrichment of fractions. To investigate the structural characteristics of antioxidants and UV-B absorbing molecules, a preparative centrifugal partition chromatography (CPC) method was developed to prepare enriched bioactive fractions from the red seaweed Solieria chordalis (Gigartinales, Solieriaceae). After a methanolic extraction of dried Solieria chordalis and liquid-liquid separation using ethyl acetate/water (v/v), the ethyl acetate phase was submitted to CPC using Arizona Y of the quaternary solvent system composed of n-heptane/ethyl acetate/methanol/water (19/1/19/1, v/v) in ascending mode. Among the fifteen collected fractions, three fractions gave up to 23.50% of DPPH radical scavenging activity. The CPC fractionation was monitored by HPLC and, four compounds exhibited UV-B absorbing capacity regarding their absorption at 310 nm.     

Simultaneous measurement of fluoroquinolones in eggs by a combination of supercritical fluid extraction and high pressure liquid chromatography

Simultaneous detection of the fluoroquinolone antibiotics ciprofloxacin, enrofloxacin, ofloxacin, and norfloxacin in eggs by a combination of supercritical fluid extraction (SFE) and high pressure liquid chromatography (HPLC) was studied. Lipid matrices that have been considered to result in poor extraction and isolation of fluoroquinolones in eggs were removed first by SFE with supercritical CO(2) alone, and then the fluoroquinolones were extracted by SFE with supercritical CO(2) containing 20% (v/v) methanol for HPLC analysis. A time-course study of the extraction of lipid matrices of eggs suggested that the SFE method successfully removed the matrices within 20 min. When the fluoroquinolones added to control eggs were extracted by SFE, the extraction efficiency was similar to that by the solvent extraction method, giving the recovery percentages from 83 to 96% in a 40 min-extraction time. The fluoroquinolones extracted from eggs by SFE were analyzed simultaneously by HPLC equipped with a fluorescence detector with detection sensitivity at about 10 ppb for the detection limit. The standard calibration profiles of fluoroquinolones showed linear responses to HPLC, showing more than 0.995 for the mean r(2) value. This is the first report of the simultaneous measurement of fluoroquinolones in eggs by a combination of SFE and HPLC. Using the SFE method allowed us to avoid extensive sample preparation such as solvent extraction and chromatographic cleanup that are basically required in extraction of fluoroquinolones.     

Isolation of four high-purity dammarane saponins from extract of Panax notoginseng by centrifugal partition chromatography coupled with evaporative light scattering detection in one operation

Introduction – Centrifugal partition chromatography (CPC), as a continuous liquid–liquid partition chromatography with no solid support matrix, combined with evaporative light scattering detection (ELSD) was employed for systematic separation and purification of weak‐chromophoric saponins from a highly valued and important traditional Chinese herbal medicine, Panax notoginseng. Objective – To separate and isolate high‐purity saponins from extract of Panax notoginseng using CPC‐ELSD with a simple and low toxicity solvent system. Methodology – Samples were preparaed by extracting the root material with acetone, treated with n‐butanol and then freeze‐dried. CPC‐ELSD was applied in the separation and detection of notoginsenoside and ginsenosides from extract of Panax notoginseng using a solvent system composed of ethyl acetate–n‐butanol–water (1:1:2, v/v/v). The saponins were analysed and identified by their retention time with high‐performance liquid chromatography (HPLC) coupled with ELSD, as well as electrospray ionisation tandem mass spectrometry (ESI‐MSⁿ ) in the negative and positive ion modes with the authentic standards. Results – A total of 9.6 mg of notoginsenoside R₁, 67.8 mg of ginsenoside Rg₁, 2.3 mg of Re and 286.5 mg of Rb₁ were purified from 487.2 mg of n‐butanol extract of P. notoginseng. The purities of obtained saponins in a single run were assessed to be over 98% by HPLC‐ELSD. Conclusion – CPC‐ELSD was proved to be a very fast and efficient tool for separation of high‐purity dammarane saponins. Copyright © 2011 John Wiley & Sons, Ltd.     

Preparative separation of chlorogenic acid by centrifugal partition chromatography from highbush blueberry leaves (Vaccinium corymbosum L.)

Introduction – Blueberries (genus Vaccinium) have gained worldwide focus because of the high anthocyanin content of their fruits. In contrast, the leaves of blueberry have not attracted any attention, even though they contain large quantities of chlorogenic acid, a strong antioxidant compound. Objective – The aim of this investigation was the quantification and preparative isolation of chlorogenic acid (5‐caffeoylquinic acid, 5‐CQA) from blueberry leaves using a new separation scheme, centrifugal partition chromatography (CPC). Methodology – A water fraction containing a high concentration of 5‐CQA (14.5% of dry weight extract) was obtained by defatting a crude methanol extract from blueberry leaves. CPC was applied to isolate 5‐CQA from this water fraction using a two‐phase solvent system of ethyl acetate–ethanol–water at a volume ratio 4:1:5 (v/v/v). The flow‐rate of mobile phase was 2 mL/min with the ascending mode while rotating at 1200 rpm. The eluate was monitored at 330 nm. The structure of chlorogenic acid in the CPC fraction was confirmed with HPLC, UV, ESI/MS and NMR spectra. Results – The HPLC chromatogram showed that the fractions collected by CPC contained chlorogenic acid with 96% purity based on peak area percentage. The total amount of chlorogenic acid isolated from 0.5 g of a water fraction was 52.9 mg, corresponding to 10.6% of the water fraction. The isolated compound was identified successively as 5‐CQA with MS (parent ion at m/z 355.1 [M + H]⁺) and ¹H NMR spectra [caffeoyl moiety in the down field (δ 6.0–8.0 ppm) and quinic acid moiety in the up field (δ 2.0–5.5 ppm)]. Conclusion – 5‐CQA was successfully isolated from blueberry leaves by the CPC method in a one‐step procedure, indicating a further potential use for blueberry leaves. Copyright © 2010 John Wiley & Sons, Ltd.     

A brown alga Sargassum fulvellum facilitates neuronal maturation and synaptogenesis

Sargassum fulvellum (Turner) C. Agardh is an edible brown macroalgae having pharmacological importance. In previous reports, we described the screening of marine algae for their neuritogenic activity in developing hippocampal neurons and found that ethanol extract of S. fulvellum (SFE) possesses promising neurite-outgrowth-promoting activity. In this study, we evaluated whether the initial neurite promoting effect of SFE was followed on the further neuronal maturation and synapse formation. SFE exhibited dose-dependent effect on neurite maturation with an optimum concentration of 5???g/mL. The initial neuronal differentiation is significantly promoted by SFE. Subsequently, compared with control culture, SFE increased the indices of axonal and dendritic developments such as the number and the length of primary processes, and branching frequencies. In addition to its effect on neurite development, SFE significantly increased the number of puncta for postsynaptic density-95, synaptic vesicle 2, and synapse (about 35%, 67%, and 125%, respectively, of control). Moreover, SFE dose-dependently protects neurons from naturally occurring death in normal culture condition. Taken together, our data demonstrate that SFE can promote neuronal maturation and synaptogenesis and support neuronal survival, suggesting the beneficial effect of this alga in nervous system.     

In vitro and in silico evaluation of fucosterol from Sargassum horridum as potential human acetylcholinesterase inhibitor

The fucosterol has been reported numerous biological activities. In this study, the activity in vitro of the fucosterol from Sargassum horridum as potential human acetylcholinesterase inhibitor was evaluated. The structural identification was obtained by nuclear magnetic resonance (NMR) spectroscopy and based on experimental data, we combined docking and molecular dynamics simulations coupled to the molecular-mechanics-generalized-born-surface-area approach to evaluating the structural and energetic basis for the molecular recognition of fucosterol and neostigmine at the binding site of acetylcholinesterase (AChE). In addition, the Lineweaver–Burk plot showed the nature of a non-competitive inhibition. The maximum velocity (V_max) and the constant of Michaelis–Menten (K_m) estimated for fucosterol (0.006 µM) were 0.015 1/V_o (ΔA/h and 6.399 1/[ACh] mM^?1, respectively. While, for neostigmine (0.14 µM), the V_max was 0.022 1/V_o (ΔA/h) and K_m of 6.726 1/[ACh] mM^?1, these results showed a more effective inhibition by fucosterol respect to neostigmine. Structural analysis revealed that neostigmine reaches the AChE binding site reported elsewhere, whereas fucosterol can act as a no-competitive and competitive acetylcholinesterase inhibitor, in agree with kinetic enzymatic experiments. Binding free energy calculations revealed that fucosterol reaches the acetylcholinesterase binding site with higher affinity than neostigmine, which is according to experimental results. Whereas the per-residue decomposition free energy analysis let us identify crucial residues involved in the molecular recognition of ligands by AChE. Results corroborate the ability of theoretical methods to provide crucial information at the atomic level about energetic and structural differences in the binding interaction and affinity from fucosterol with AChE.

Communicated by Ramaswamy H. Sarma     

Purification and chemical characterization of antimicrobial compounds from a new soil isolate Streptomyces rimosus MTCC 10792

A new isolate of Streptomyces sp. from soil of state Chhattisgarh (India) having broad spectrum antibacterial and antifungal activity was obtained. The active strain was identified as Streptomyces rimosus subsp. rimosus with accession number MTCC 10792 based on physiological, biochemical characteristics and 16S rRNA sequence homology studies. Antimicrobial compound produced by S. rimosus was tested against the drug resistance pathogens by the Bauer and Kirby method. The crude active metabolite was extracted using solvent n-butanol and purified by silica column chromatography and HPLC method. The physicochemical characteristics of the one purified compound viz. color, melting point, solubility, elemental analysis, ESIMS, IR, UV, 1HNMR, ¹³CNMR and chemical reactions have been investigated. Purified antimicrobial compound produced by S. rimosus MTCC 10792 at concentration 25 μg/mL showed antitubercular activity against Mycobacterium tuberculosis H37Rv, Mycobacterium tuberculosis H37R as well as broad activity against all tested bacterial and fungal pathogens.     

Sterols of Agarum cribosum: desmosterol in a brown alga

The sterol composition of the cold water brown alga Agarum cribosum was determined by GC—MS. Six of the seven sterols found were identified as stigmata-5,(E)-24(28)-dien-3β-ol (fucosterol), 24-methylenecholest-5-en-3β-ol (24-methylenecholesterol), cholest-5-en-3β-ol (cholesterol), 3β-hydroxycholest-5-en-24-one (24-ketocholesterol), 24ξ-stigmasta-5,28-diene-3β,24-diol (saringosterol) and cholesta-5, 24-dien-3β-ol (desmosterol).     

Structures of some botryococcenes: branched hydrocarbons from the b-race of the green alga Botryococcus braunii

Nine branched hydrocarbons of the botryococcene type (C_nH_2n-10 30 ? n ? 37) have been isolated from the green alga Botryococcus braunii. Hydrocarbon mixtures were recovered from wild algae collected in fresh water lakes or from the same strains growing in laboratory; they were further separated by reversed-phase, and in some cases by normal phase, HPLC. From chemical investigations, GC/MS analyses, ¹H and ¹³C NMR spectroscopy, the structures of four new botryococcenes (one C₃₃H₅₆, two C₃₄H₅₈ and one C₃₇H₆₄) were elucidated.     

UV-A/B radiation rapidly activates photoprotective mechanisms in Chlamydomonas reinhardtii

Conversion of light energy into chemical energy through photosynthesis in the chloroplasts of photosynthetic organisms is essential for photoautotrophic growth, and non-photochemical quenching (NPQ) of excess light energy prevents the generation of reactive oxygen species and maintains efficient photosynthesis under high light. In the unicellular green alga Chlamydomonas reinhardtii, NPQ is activated as a photoprotective mechanism through wavelength-specific light signaling pathways mediated by the phototropin (blue light) and ultra-violet (UV) light photoreceptors, but the biological significance of photoprotection activation by light with different qualities remains poorly understood. Here, we demonstrate that NPQ-dependent photoprotection is activated more rapidly by UV than by visible light. We found that induction of gene expression and protein accumulation related to photoprotection was significantly faster and greater in magnitude under UV treatment compared with that under blue- or red-light treatment. Furthermore, the action spectrum of UV-dependent induction of photoprotective factors implied that C. reinhardtii senses relatively long-wavelength UV (including UV-A/B), whereas the model dicot plant Arabidopsis (Arabidopsis thaliana) preferentially senses relatively short-wavelength UV (mainly UV-B/C) for induction of photoprotective responses. Therefore, we hypothesize that C. reinhardtii developed a UV response distinct from that of land plants.

In contrast to land plants, which sense short-wave UV light, the unicellular green alga Chlamydomonas reinhardtii senses long-wavelength UV light for photoprotective responses.     

Assay of the antiangiogenic compound TNP-470, and one of its metabolites, AGM-1883, by reversed-phase high-performance liquid chromatography in plasma

This paper describes a reversed-phase, high-performance liquid chromatographic (HPLC) method for the isolation, detection, and quantification of TNP-470 (I) and one of its active metabolites, AGM-1883 (II), from plasma. These compounds are initially extracted from plasma with an organic solvent and then separated from one another on a C₁₈ column. Those fractions eluting from the C₁₈ column and containing either I or II are then derivatized through their epoxide moieties with sodium 8-quinolinethiolate (SQT). This derivatization produces fluorescent species that are isolated and quantified by a second reversed-phase HPLC analysis. The assay yields a lower limit of reliable quantification of 2.5 ng/ml and is linear to a concentration at least as high as 160 ng/ml. The inter-assay percent coefficient of variation is less than 18%.     

Antifungals and acetylcholinesterase inhibitors from the stem bark of Croton heliotropiifolius

The ethanolic extract of the stem bark of Croton heliotropiifolius Kunth (Euphorbiaceae) showed significant in vitro inhibition of acetylcholinesterase using a dilution spectrophotometric assay and antifungal activity against Candida albicans with a thin layer chromatography (TLC) bioautographic assay. In order to isolate the active compounds, bioassay-guided fractionation was undertaken using HPLC to localize the active compounds. Different zones of the HPLC-UV chromatogram were linked to acetylcholinesterase inhibition or to antifungal activities. In parallel to this HPLC-based activity profiling, HPLC-PDA-ESI-MS and HPLC-TOF-HRMS were used for the early identification of some of the compounds present. The targeted isolation of the active compounds was performed by medium pressure liquid chromatography (MPLC-UV) and further semi-preparative HPLC. Using this approach, nine compounds were isolated, one of them being a new indole alkaloid derivative. The structures of the isolated compounds were elucidated by spectroscopic methods including UV, NMR, MS and HRMS.     

Antimicrobial activity of Calotropis procera Ait. (Asclepiadaceae) and isolation of four flavonoid glycosides as the active constituents

Antimicrobial activity of solvent extracts and flavonoids of Calotropis procera growing wild in Saudi Arabia was evaluated using the agar well-diffusion method. A bioassay-guided fractionation of the crude flavonoid fraction (Cf₃) of MeOH extract which showed the highest antimicrobial activity led to the isolation of four flavonoid glycosides as the bioactive constituents. Structure of compounds have been elucidated using physical and spectroscopic methods including (UV, IR, ¹H, ¹³C-NMR, DEPT, 2D ¹H–¹H COSY, HSQC, HMBC and NOESY). Compounds were found to be the 3-O-rutinosides of quercetin, kaempferol and isorhamnetin, besides the flavonoid 5-hydroxy-3,7-dimethoxyflavone-4′-O-β-glucopyranoside. Most of the isolated extracts showed antimicrobial activity against the test microorganisms, where the crude flavonoid fraction was the most active, diameter of inhibition zones ranged between 15.5 and 28.5 mm against the tested bacterial strains, while reached 30 mm against the fungal Candida albicans. The minimal inhibitory concentrations varied from 0.04 to 0.32 mg/ml against all of the tested microorganisms in case of the crude flavonoid fraction. Quercetin-3-O-rutinoside showed superior activity over the remainder flavonoids. The Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) were more susceptible than the Gram-negative (Pseudomonas aeruginosa and Salmonella enteritidis) and the yeast species were more susceptible than the filamentous fungi. The study recommend the use of such natural products as antimicrobial biorationals.     

The effect of re-dissolution solvents and HPLC columns on the analysis of mycosporine-like amino acids in the eulittoral macroalgae <Emphasis Type="Italic">Prasiola crispa</Emphasis> and <Emphasis Type="Italic">Porphyra umbilicalis</Emphasis>

Many macroalgal species that are regularly exposed to high solar radiation such as the eulittoral green alga Prasiola crispa and the red alga Porphyra umbilicalis synthesize and accumulate high concentrations of mycosporine-like amino acids (MAAs) as UV-sunscreen compounds. These substances are typically extracted with a widely used standard protocol following quantification by various high performance liquid chromatography (HPLC) techniques. However, further preparation steps prior to HPLC analysis as well as different HPLC column types have not been systematically checked regarding separation quality and reproducibility. Therefore pure methanol, distilled water and HPLC eluent were evaluated as re-dissolution solvent for dried Prasiola and Porphyra extracts, which were subsequently analyzed on three reversed-phase C8 and C18 HPLC columns. The data indicate that distilled water and the HPLC eluent gave almost identical peak patterns and MAA contents on the C8 and C18 columns. In contrast, the application of the widely used methanol led to double peaks or even the loss of specific peaks as well as to a strong decline in total MAA amounts ranging from about 35% of the maximum in P. crispa to 80% of the maximum in P. umbilicalis. Consequently, methanol should be avoided as re-dissolution solvent for the HPLC sample preparation. An improved protocol for the MAA analysis in macroalgae in combination with a reliable C18 column is suggested.     

Effect of 1-n-Decylimidazole on Gibberellin Biosynthesis in Tan-ginbozu,a Dwarf Variety of Rice

Previous structural studies of less-polar dimers in autoxidized methyl linoleate (ML) have been extended to polar dimers. After isolation by successive silicic acid and gel permeation chromatography, the dimeric fraction of linoleate was separated into two major fractions, A₁ and A₂, according to their polarities. The polar dimers (A₁) were further fractionated by HPLC either directly or after reduction with triphenyl phosphine on a micro silica column. Isolated subfractions were characterized by UV, IR, GC-MS and FD-MS after suitable derivatizations. FD-MS of all these dimers showed a molecular ion peak which corresponds to 2 × ML + 6 × O and the reduction of each subfraction with stannous chloride gave equimolar amounts of 9 and 13-hydroxy octadecadienoate, and 9, 10, 13 and/or 9, 12, 13-trihydroxy octadecenoate. These results combined with others show that the A₁ dimers are composed of isomeric mixtures containing a peroxide bridge linking a methyl octadecadienoate and a 9, 12 and/or 10, 13-dihydroperoxy octadecenoate across C-9 and/or 13 on each of them.     

Changes in Phenolic Compounds and Cellular Ultrastructure of Arctic and Antarctic Strains of Zygnema (Zygnematophyceae, Streptophyta) after Exposure to Experimentally Enhanced UV to PAR Ratio

Ultraviolet (UV) radiation has become an important stress factor in polar regions due to anthropogenically induced ozone depletion. Although extensive research has been conducted on adaptations of polar organisms to this stress factor, few studies have focused on semi-terrestrial algae so far, in spite of their apparent vulnerability. This study investigates the effect of UV on two semi-terrestrial arctic strains (B, G) and one Antarctic strain (E) of the green alga Zygnema, isolated from Arctic and Antarctic habitats. Isolates of Zygnema were exposed to experimentally enhanced UV A and B (predominant UV A) to photosynthetic active radiation (PAR) ratio. The pigment content, photosynthetic performance and ultrastructure were studied by means of high-performance liquid chromatography (HPLC), chlorophyll a fluorescence and transmission electron microscopy (TEM). In addition, phylogenetic relationships of the investigated strains were characterised using rbcL sequences, which determined that the Antarctic isolate (E) and one of the Arctic isolates (B) were closely related, while G is a distinct lineage. The production of protective phenolic compounds was confirmed in all of the tested strains by HPLC analysis for both controls and UV-exposed samples. Moreover, in strain E, the content of phenolics increased significantly (p?=?0.001) after UV treatment. Simultaneously, the maximum quantum yield of photosystem II photochemistry significantly decreased in UV-exposed strains E and G (p?<?0.001), showing a clear stress response. The phenolics were most probably stored at the cell periphery in vacuoles and cytoplasmic bodies that appear as electron-dense particles when observed by TEM after high-pressure freeze fixation. While two strains reacted moderately on UV exposure in their ultrastructure, in strain G, damage was found in chloroplasts and mitochondria. Plastidal pigments and xanthophyll cycle pigments were investigated by HPLC analysis; UV A- and UV B-exposed samples had a higher deepoxidation state as controls, particularly evident in strain B. The results indicate that phenolics are involved in UV protection of Zygnema and also revealed different responses to UV stress across the three strains, suggesting that other protection mechanisms may be involved in these organisms.