Construction of dual-chiral covalent organic frameworks for enantioselective separation.

Developing novel chiral stationary phases (CSPs) with versatility is of great importance in enantiomer separation. This study fabricated a dual-chiral covalent organic framework (PA-CA COF) via successive post-synthetic modifications. The chiral trans-1,2-cyclohexanediamine (CA) and (D)-penicillamine (PA) groups were periodically aligned within nanochannels of the COF, allowing selective recognition of enantiomers through intermolecular interactions. It can be a versatile high-performance liquid chromatography (HPLC) CSP for separating a wide range of enantiomers, including chiral pharmaceutical intermediates and chiral drugs. With separation performance comparable to commercial chiral columns and even greater versatility, the PA-CA COF@SiO2 column held promise for practical applications. Chiral separation results combined with molecular simulation indicated that the mixed mode of PA and CA resulted in the broad separation capability of PA-CA COF. The introduction of the dual-chiral COFs concept opens up a new avenue for chiral recognition and separation, holding great potential for practical enantiomer separation.

Antifungal mono- and dimeric nitrogenous bisabolene derivatives from a sponge in the order Bubarida from Futuna Islands.

An abundant sponge of the order Bubarida was selected for further chemical investigation following biological and chemical screening of sponges collected from Futuna Islands in the Indo-Pacific. Ten new nitrogenous bisabolene derivatives were isolated and identified: the monomeric theonellin formamide analogues named bubaridins A-F (1-6) with unusual oxidised linear chains, and the first isocyanide/formamide dimeric and cyclised bisabolenes 7-9. The structure elucidation of these nitrogenous bisabolenes involved HRESIMS, NMR, and ECD analyses, and the chiral compounds were found to be racemates. A biosynthetic hypothesis for the production of these metabolites is proposed and some chemotaxonomic considerations are discussed. Furthermore, the antimicrobial and antitumoral activity were evalutated and the trans-dimer theonellin isocyanide (7) was shown to exhibit potent and selective antifungal activity.

Shinorine ameliorates chromium induced toxicity in zebrafish hepatocytes through the facultative activation of Nrf2-Keap1-ARE pathway.

Hexavalent chromium, a heavy metal toxicant, abundantly found in the environment showed hepatotoxic potential in zebrafish liver and instigated the Nrf2-Keap1-ARE pathway as a cellular stress response as reported in our previous studies. In the present study we have evaluated the ameliorating effect of shinorine, a mycosporine like amino acid (MAAs) and a mammalian Keap1 antagonist against chromium induced stress in zebrafish hepatocytes. Shinorine was found to be effective in increasing the cell viability of chromium treated hepatocytes through curtailing the cellular ROS content. Trigonelline, an Nrf2 inhibitor was found to reduce the viability of hepatocyte cultures co-exposed to shinorine and chromium. In other words, trigonelline being an Nrf2 blocker neutralised the alleviating effect of shinorine. This indicated that shinorine mediated cyto-protection in Cr [VI]-intoxicated cells is Nrf2 dependent. Further, qRT-PCR analysis revealed comparatively higher expression of nfe2l2 and nqo1 in shinorine + chromium treated hepatocytes than cells exposed to chromium alone indicating a better functioning of Nrf2-Keap1-Nqo1 axis. To further confirm if shinorine can lead to disruption of Nrf2-Keap1 interaction in zebrafish hepatocytes and render cytoprotection to chromium exposure, our in silico analysis through molecular docking revealed that shinorine could bind to the active amino acid residues of the DGR domain, responsible for Nrf2-Keap1 interaction of all the three Keap1s evaluated. This is the first report about shinorine that ameliorates chromium induced toxicity through acting as an Nrf2-Keap1 interaction disruptor. We additionally carried out in-silico pharmacokinetic and ADMET studies to evaluate druglikeness of shinorine whose promising results indicated its potential to be developed as an ideal therapeutic candidate against toxicant induced pathological conditions.

Tuning the selectivity of molecularly imprinted polymer extraction of arylcyclohexylamines: From class-selective to specific.

A molecularly imprinted polymer (MIP) has been prepared in presence of 3-hydroxy phencyclidine (3-OH PCP) as template by bulk polymerization using N,N-dimethylformamide, as porogenic solvent, for the selective solid-phase extraction (SPE) of arylcyclohexylamines from oral fluids. Experimental variables of the extraction procedure have been studied in order to increase both, extraction recovery of 3-OH PCP, used as model analyte, and imprinting factor. By modifying the composition of the washing solvent, the selectivity of the MIP extraction procedure can be tuned, moving from an arylcyclohexylamine selective method to a 3-OH PCP specific method. The applicability of the synthesized MIP was evaluated by the analysis of oral fluids spiked with 3-OH PCP at different concentration levels, extracted using both recommended SPE procedures and analyzed by ion mobility spectrometry. Recovery values ranging from 70 to 101% and a limit of detection of 15 µg L-1 were obtained.

UVA and UVB Photoprotective Capabilities of Topical Formulations Containing Mycosporine-like Amino Acids (MAAs) through Different Biological Effective Protection Factors (BEPFs).

The safety and stability of synthetic UV-filters and the procedures for evaluating the photoprotective capability of commercial sunscreens are under continuous review. The influence of pH and temperature stressors on the stability of certain Mycosporine-like amino acids (MAAs) isolated at high purity levels was examined. MAAs were highly stable at room temperature during 24 h at pH 4.5⁻8.5. At 50 °C, MAAs showed instability at pH 10.5 while at 85 °C, progressive disappearances were observed for MAAs through the studied pH range. In alkaline conditions, their degradation was much faster. Mycosporine-serinol and porphyra-334 (+shinorine) were the most stable MAAs under the conditions tested. They were included in four cosmetically stable topical sunscreens, of which the Sun Protection Factor (SPF) and other Biological Effective Protection Factors (BEPFs) were calculated. The formulation containing these MAAs showed similar SPF and UVB-BEPFs values as those of the reference sunscreen, composed of synthetic UV absorbing filters in similar percentages, while UVA-BEPFs values were slightly lower. Current in vitro data strongly suggest that MAAs, as natural and safe UV-absorbing and antioxidant compounds, have high potential for protection against the diverse harmful effects of solar UV radiation. In addition, novel complementary in vitro tests for evaluation of commercial sunscreens efficacy are proposed.

Separation of structurally related primary aliphatic amines using hydrophilic interaction chromatography with fluorescence detection after postcolumn derivatization with o-phthaldialdehyde/mercaptoethanol.

The retention behavior of primary aliphatic amines (homologous series of aliphatic alkyl amines and cycloalkyl amines) and positional isomers of alkylamines in the hydrophilic interaction chromatography mode was studied. The study was carried out on a TSKgel Amide-80 column followed by postcolumn derivatization with fluorescence detection to describe the retention mechanism of tested compounds. The effect of chromatographic conditions including column temperature, acetonitrile content in the mobile phase, mobile phase pH (ranging from 3.5 to 6.8), and salt concentration in the mobile phase was investigated. The final mobile phase consisted of acetonitrile and solution of 20 mM potassium formate pH 3.5 in ratio 80:20 v/v. The analyses were carried out at mobile phase flow rate of 1.0 mL/min and the column temperature of 20°C. The developed method was fully validated in terms of linearity, sensitivity (limit of detection and limit of quantification), accuracy, and precision according to International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use guidelines. The proposed new methods were proved to be highly sensitive, simple, and rapid, and were successfully applied to the determinations of isopropylamine, cyclohexylamine, and cyclopropylamine in relevant active pharmaceutical ingredients.

Analysis of Mycosporine-Like Amino Acids in Selected Algae and Cyanobacteria by Hydrophilic Interaction Liquid Chromatography and a Novel MAA from the Red Alga Catenella repens.

Mycosporine-like amino acids (MAAs), a group of small secondary metabolites found in algae, cyanobacteria, lichens and fungi, have become ecologically and pharmacologically relevant because of their pronounced UV-absorbing and photo-protective potential. Their analytical characterization is generally achieved by reversed phase HPLC and the compounds are often quantified based on molar extinction coefficients. As an alternative approach, in our study a fully validated hydrophilic interaction liquid chromatography (HILIC) method is presented. It enables the precise quantification of several analytes with adequate retention times in a single run, and can be coupled directly to MS. Excellent linear correlation coefficients (R² > 0.9991) were obtained, with limit of detection (LOD) values ranging from 0.16 to 0.43 µg/mL. Furthermore, the assay was found to be accurate (recovery rates from 89.8% to 104.1%) and precise (intra-day precision: 5.6%, inter-day precision ≤6.6%). Several algae were assayed for their content of known MAAs like porphyra-334, shinorine, and palythine. Liquid chromatography-mass spectrometry (LC-MS) data indicated a novel compound in some of them, which could be isolated from the marine species Catenella repens and structurally elucidated by nuclear magnetic resonance spectroscopy (NMR) as (E)-3-hydroxy-2-((5-hydroxy-5-(hydroxymethyl)-2-methoxy-3-((2-sulfoethyl)amino)cyclohex-2-en-1-ylidene)amino) propanoic acid, a novel MAA called catenelline.

Isolation and Total Synthesis of Kirkamide, an Aminocyclitol from an Obligate Leaf Nodule Symbiont.

The new C7N aminocyclitol kirkamide (1) was isolated from leaf nodules of the plant Psychotria kirkii by using a genome-driven (1)H NMR-guided fractionation approach. The structure and absolute configuration were elucidated by HRMS, NMR, and single-crystal X-ray crystallography. An enantioselective total synthesis was developed, which delivered kirkamide (1) on a gram scale in 11 steps and features a Ferrier carbocyclization and a Pd-mediated hydroxymethylation. We propose that kirkamide is synthesized by Candidatus Burkholderia kirkii, the obligate leaf symbiont of Psychotria kirkii. Kirkamide (1) was shown to be toxic to aquatic arthropods and insects, thus suggesting that bacterial secondary metabolites play a protective role in the Psychotria/Burkholderia leaf nodule symbiosis.

Complementary UV-absorption of mycosporine-like amino acids and scytonemin is responsible for the UV-insensitivity of photosynthesis in Nostoc flagelliforme.

Mycosporine-like amino acids (MAAs) and scytonemin are UV-screening compounds that have presumably appeared early in the history of life and are widespread in cyanobacteria. Natural colonies of the UV-insensitive Nostoc flagelliforme were found to be especially rich in MAAs (32.1 mg g DW(-1)), concentrated in the glycan sheath together with scytonemin. MAAs are present in the form of oligosaccharide-linked molecules. Photosystem II activity, measured using PAM fluorescence and oxygen evolution, was used as a most sensitive physiological parameter to analyse the effectiveness of UV-protection. Laboratory experiments were performed under controlled conditions with a simulated solar radiation specifically deprived of UV-wavebands with cut-off filters (295, 305, 320, 345 and 395 nm). The UV-insensitivity of N. flagelliforme was found to cover the whole UV-A (315-400 nm) and UV-B (280-320 nm) range and is almost certainly due to the complementary UV-absorption of MAAs and scytonemin. The experimental approach used is proposed to be suitable for the comparison of the UV-protection ability in organisms that differ in their complement of UV-sunscreen compounds. Furthermore, this study performed with a genuinely terrestrial organism points to the relevance of marine photoprotective compounds for life on Earth, especially for the colonization of terrestrial environments.

Membrane bioreactor treatment of a simulated metalworking fluid wastewater containing ethylenediaminetetraacetic acid and dicyclohexylamine.

Membrane bioreactors (MBRs) have been installed at automotive plants to treat metalworking fluid (MWF) wastewaters, which are known to contain toxic and/or recalcitrant organic compounds. A laboratory study was conducted to evaluate treatment of a simulated wastewater prepared from a semisynthetic MWF, which contains two such compounds, dicyclohexylamine (DCHA) and ethylenediaminetetraacetic acid (EDTA). Primary findings were as follows: During stable operating periods, almost all chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), and EDTA were removed (by > 96%). During somewhat unstable periods, COD removal was still extremely robust, but removal of EDTA and TKN were sensitive to prolonged episodes of low dissolved oxygen. Nitrogen mass balance suggested 30 to 40% TKN removal by assimilation and 60 to 70% by nitrification (including up to 34% TKN removal via subsequent denitrification). Dicyclohexylamine appeared to be readily biodegraded. Maximum DCHA and EDTA degradation rates between pH 7 and 8 were found. An Arthrobacter sp. capable of growth on DCHA as the sole source of carbon and energy was isolated.

[Regulation of polyamine and cancer].

This review describes my work in the field of polyamine research for the last 35 years. My research started with developing the improved synthesis of decarboxylated S-adenosylmethionine and then moved to the purification of spermidine synthase from rat prostate. I also took considerable efforts to find the synthetic procedure for various polyamines with high yield in order to prepare (15)N-labeled polyamines. On the basis of these methodological work, I searched for the inhibitor of spermidine synthase and found trans-4-methylcyclohexylamine (MCHA), the most effective one at the present time. I also developed a new analytical method for polyamines using stable isotope and ionspray ionization mass spectrometry (IS-MS). Based on these studies I examined the role of polyamines in liver regeneration and found that oral administration of MCHA effectively changed the concentration of polyamines and inhibited the hepatic growth. I also found the close relationship between the concentration ratio of spermidine to spermine and the extent of liver regeneration. These results may shed new light on the control of cell growth by polyamine in vivo.

Mycosporine-like amino acid (MAAs) production by Heterocapasa sp. (Dinophyceae) in indoor cultures.

The possibility of using mycosporine-like amino acids (MAAs), with an apparent sunscreen function in nature, as ultraviolet radiation (UVR) blockers to prevent skin injury has been raised by diverse authors. Production of MAAs by the dinoflagellate Heterocapsa sp. (Dinophyceae) is shown here. Three major peaks with absorption maxima at 330.8, 332.0 and 333.2 nm were detected by high performance liquid chromatography (HPLC) analysis of methanolic extracts in all tested conditions. Analysis of crude extract by mass spectroscopy with electrospray ionization (MS-EI) showed a set of molecular ions ([M+H](+)) with main peaks being at m/z 242.4, 288.4, 303.3 and 333.3 u.m.a. According to these data, along with retention times, the MAA profile of Heterocapsa sp. is assumed to be composed of shinorine (lambda(max)=334 nm), mycosporine-2-glycine (lambda(max)=331 nm) and palythinol (lambda(max)=332 nm). A constitutive MAA content of about 4 microg (10(6) cells)(-1) was measured under exposure to PAR only. A maximal accumulation of MAA per culture volume of 1.1 mg l(-1) was obtained after 72 h of exposure to PAR+UVA, while the highest production rate (0.025 mg l(-1) h(-1)) was computed after 24 h of exposure to PAR+UVA+UVB.

Metabolism of cyclamate and its conversion to cyclohexylamine.

Since cyclamates were first introduced in the early 1950s, arguments have raged over the potential carcinogenicity of this artificial sweetener. Concern over the safety of cyclamates arises from observations that some individuals and experimental animals can metabolize cyclamate to cyclohexylamine and that cyclohexylamine has been shown to produce testicular atrophy in experimental animals. This study examines the absorption, excretion, and metabolism of cyclamate, particularly its conversion to cyclohexylamine. In addition, the potential toxicity and pharmacology of cyclohexylamine are discussed.

Isolation and identification of minor components of commercial kanamycin.

A fraction enriched in the minor components of the kanamycin complex was prepared from a commercial sample. The enriched fraction was subjected to Amberlite CG-50 and Dowex 1-X2 column chromatography. Two minor components were isolated in addition to the known A, B, and C components. These congeners were identified as paromamine and 6-o-(3-amino-3-deoxy-alpha-d-glucopyranosyl)- deoxystreptamine. The identification was based on degradation and mass spectral studies.