A rapid enantioseparation system of capillary electrochromatography modified by electrostatic adsorption with transfersomes

Transfersomes were a special kind of nanomaterials with higher deformability and flexibility. A rapid method for coated-column preparation using anionic transfersomes as a coating material by electrostatic adsorption was developed. With carboxymethyl-β-cyclodextrin added in running buffer as the chiral selector, the capillary electrochromatography enantioseparation system based on the transfersomes-coated column modified by electrostatic adsorption was established for the first time. Propranolol and metoprolol acted as model drugs to evaluate the enantioseparation performance, these two basic drugs achieved baseline separation with satisfactory resolution and selection factor in this transfersomes-electrochromatography system but only partial separation in bare column system. In order to get the optimal separation condition, concentration of chiral selector, buffer pH, and applied voltage were systematically investigated. A rapid and efficient enantioseparation electrochromatography system was established and showed that transfersomes as the stationary phase could efficiently improve chiral separation effect.     

Syntheses of all eight stereoisomers of conidendrin

ABSTRACT

All eight stereoisomers of conidendrin were synthesized from (1 R,2 S,3 S)-1-(4-benzyloxy-3-methoxyphenyl)-3-(4-benzyloxy-3-methoxybenzyl)-2- hydroxymethyl-1,4-butanediol ((+)-4) and its enantiomer with high optical purity. The configurations at 4-positions of the conidendrin stereoisomers were constructed by intramolecular Friedel-Crafts reaction of protected 4. After conversion to tetrahydronaphthalene intermediate 7a, the 2- and 3-position of tetrahydronaphthalene structure 7a were converted to 3a- and 9a-position of (+)-α-conidendrin (3a), respectively. By the epimerization process of 2- or 3-position of 7a, the other diastereomers were obtained. All enantiomers were also synthesized from (?)-4.     

Identification of novel inhibitors for the tyrosyl-DNA-phosphodiesterase 1 (Tdp1) mutant SCAN1 using virtual screening

Spinocerebellar ataxia syndrome with axonal neuropathy (SCAN1) is a debilitating neurological disease that is caused by the mutation the Tyrosyl-DNA phosphodiesterase 1 (TDP1) DNA repair enzyme. The crucial His493 in TDP1′s binding site is replaced with an arginine amino acid residue rendering the enzyme dysfunctional. A virtual screen was performed against the homology model of SCAN1 and seventeen compounds were identified and tested in a novel SCAN1 specific biochemical assay. Six compounds showed activity with IC₅₀ values between 3.5 and 25.1 µM. The most active ligand 5 (3.5 µM) is a dicoumarin followed by a close structural analogue 6 at 6.0 µM. A less potent series of β-carbolines (14 and 15) was found with potency in the mid-teens. According to molecular modelling an excellent fit for the active ligands into the binding pocket is predicted. To the best of our knowledge, data on inhibitors of the mutant form of TDP1 has not been reported previously. The virtual hits were also tested for wild type TDP1 activity and all six SCAN1 inhibitors are potent for the former, e.g., ligand 5 has a measured IC₅₀ at 99 nM.In the last decade, TDP1 is considered as a promising target for adjuvant therapy against cancer in combination with Topoisomerase 1 poisons. The active ligands are mostly non-toxic to cancer cell lines A-549, T98G and MCF-7 as well as the immortalized WI-38 human fetal lung cells. Furthermore, ligands 5 and 7, show promising synergy in conjunction with topotecan, a clinically used topoisomerase 1 anticancer drug. The active ligands 5, 7, 14 and 15 have a good balance of the physicochemical properties required for oral bioavailability making the excellent candidates for further development.     

Small-molecule active pharmaceutical ingredients of approved cancer therapeutics inhibit human aspartate/asparagine-β-hydroxylase

Human aspartate/asparagine-β-hydroxylase (AspH) is a 2-oxoglutarate (2OG) dependent oxygenase that catalyses the hydroxylation of Asp/Asn-residues of epidermal growth factor-like domains (EGFDs). AspH is reported to be upregulated on the cell surface of invasive cancer cells in a manner distinguishing healthy from cancer cells. We report studies on the effect of small-molecule active pharmaceutical ingredients (APIs) of human cancer therapeutics on the catalytic activity of AspH using a high-throughput mass spectrometry (MS)-based inhibition assay. Human B-cell lymphoma-2 (Bcl-2)-protein inhibitors, including the (R)-enantiomer of the natural product gossypol, were observed to efficiently inhibit AspH, as does the antitumor antibiotic bleomycin A₂. The results may help in the design of AspH inhibitors with the potential of increased selectivity compared to the previously identified Fe(II)-chelating or 2OG-competitive inhibitors. With regard to the clinical use of bleomycin A₂ and of the Bcl-2 inhibitor venetoclax, the results suggest that possible side-effects mediated through the inhibition of AspH and other 2OG oxygenases should be considered.     

Rational design of cell-permeable cyclic peptides containing a d-Pro-l-Pro motif

Cyclic peptides are capable of binding to challenging targets (e.g., proteins involved in protein-protein interactions) with high affinity and specificity, but generally cannot gain access to intracellular targets because of poor membrane permeability. In this work, we discovered a conformationally constrained cyclic cell-penetrating peptide (CPP) containing a d-Pro-l-Pro motif, cyclo(AFΦrpPRRFQ) (where Φ is l-naphthylalanine, r is d-arginine, and p is d-proline). The structural constraints provided by cyclization and the d-Pro-l-Pro motif permitted the rational design of cell-permeable cyclic peptides of large ring sizes (up to 16 amino acids). This strategy was applied to design a potent, cell-permeable, and biologically active cyclic peptidyl inhibitor, cyclo(Y^pVNFΦrpPRR) (where Y^p is l-phosphotyrosine), against the Grb2 SH2 domain. Multidimensional NMR spectroscopic and circular dichroism analyses revealed that the cyclic CPP as well as the Grb2 SH2 inhibitor assume a predominantly random coil structure but have significant β-hairpin character surrounding the d-Pro-l-Pro motif. These results demonstrate cyclo(AFΦrpPRRFQ) as an effective CPP for endocyclic (insertion of cargo into the CPP ring) or exocyclic delivery of biological cargos (attachment of cargo to the Gln side chain).     

Influence of manganese exposure on cognitive function,plasma APP and Aβ levels in older men

BackgroundElevated manganese (Mn) exposure impairs cognition in adults and children, but the association between Mn and cognitive function in elderly people is unclear. Previous studies have linked Mn neurotoxicity in AD to Aβ-dependent mechanisms. However, the association between Mn and plasma APP and Aβ in the general elderly population remains unknown. This study aimed to investigate the association between Mn exposure and cognitive function, plasma APP and plasma Aβ in older adults.MethodsCognitive abilities in 375 men aged 60 and older in Guangxi, China were assessed using the Mini-Mental State Examination (MMSE) and cognitive impairment were identified using education-stratified cut-off points of MMSE scores. Urinary Mn levels and plasma APP, and Aβ levels were measured using ICP-MS and ELISA, respectively.ResultsA total of 109 (29.07 %) older men were identified as having cognitive impairment. The median urinary Mn level was 0.22 μg/g creatinine. Urinary Mn levels were negatively correlated with MMSE scores (β = −1.35, 95 % CI: −2.65 to −0.06; p = 0.041). In addition, higher concentrations of urinary manganese were associated with a greater risk of cognitive impairment (OR = 2.03, 95 % CI: 1.14–3.59; comparing the highest and lowest manganese; p = 0.025). Moreover, plasma APP levels were inversely associated with urinary Mn levels (r = −0.123, p = 0.020), and positively associated with MMSE scores (r = 0.158, p = 0.002). Surprisingly, no correlations were observed between plasma Aβ42, Aβ40, Aβ40/Aβ42, or Aβ42/Aβ40 and urinary Mn levels and MMSE scores.ConclusionThese results suggested that Mn exposure is negatively associated with older men’s cognition and plasma APP levels, but not plasma Aβ levels.     

Plant apocarotenoids: from retrograde signaling to interspecific communication

Carotenoids are isoprenoid compounds synthesized by all photosynthetic and some non-photosynthetic organisms. They are essential for photosynthesis and contribute to many other aspects of a plant's life. The oxidative breakdown of carotenoids gives rise to the formation of a diverse family of essential metabolites called apocarotenoids. This metabolic process either takes place spontaneously through reactive oxygen species or is catalyzed by enzymes generally belonging to the CAROTENOID CLEAVAGE DIOXYGENASE family. Apocarotenoids include the phytohormones abscisic acid and strigolactones (SLs), signaling molecules and growth regulators. Abscisic acid and SLs are vital in regulating plant growth, development and stress response. SLs are also an essential component in plants’ rhizospheric communication with symbionts and parasites. Other apocarotenoid small molecules, such as blumenols, mycorradicins, zaxinone, anchorene, β-cyclocitral, β-cyclogeranic acid, β-ionone and loliolide, are involved in plant growth and development, and/or contribute to different processes, including arbuscular mycorrhiza symbiosis, abiotic stress response, plant–plant and plant–herbivore interactions and plastid retrograde signaling. There are also indications for the presence of structurally unidentified linear cis-carotene-derived apocarotenoids, which are presumed to modulate plastid biogenesis and leaf morphology, among other developmental processes. Here, we provide an overview on the biology of old, recently discovered and supposed plant apocarotenoid signaling molecules, describing their biosynthesis, developmental and physiological functions, and role as a messenger in plant communication.