Further Investigation of the Mediterranean Sponge Axinella polypoides: Isolation of a New Cyclonucleoside and a New Betaine

An exhaustive exploration into the metabolic content of the Mediterranean sponge Axinella-polypoides resulted in the isolation of the new betaine 5 and the new cyclonucleoside 8. The structures of the new metabolites were elucidated by spectroscopic methods assisted by computational methods. The analysis also provided evidence that the sponge does not elaborate pyrrole-imidazole alkaloids (PIAs) but, interestingly, it was shown to contain two already known cyclodipeptides, compounds 9 (verpacamide A) and 10

Mumijo Traditional Medicine: Fossil Deposits from Antarctica (Chemical Composition and Beneficial Bioactivity)

Mumijo is a widely used traditional medicine, especially in Russia, Altai Mountains, Mongolia, Iran Kasachstan and in Kirgistan. Mumijo preparations have been successfully used for the prevention and treatment of infectious diseases; they display immune-stimulating and antiallergic activity as well. In the present study, we investigate the chemical composition and the biomedical potential of a Mumijo(-related) product collected from the Antarctica. The yellow material originates from the snow petrels, Pagodroma nivea. Extensive purification and chemical analysis revealed that the fossil samples are a mixture of glycerol derivatives. In vitro experiments showed that the Mumijo extract caused in cortical neurons a strong neuroprotective effect against the apoptosis-inducing amyloid peptide fragment β-fragment 25–35 (Aβ25–35). In addition, the fraction rich in glycerol ethers/wax esters displayed a significant growth-promoting activity in permanent neuronal PC12 cells. It is concluded that this new Mumijo preparation has distinct and marked neuroprotective activity, very likely due to the content of glycerol ether derivatives

Aplisulfamines, New Sulfoxide-Containing Metabolites from an Aplidium Tunicate: Absolute Stereochemistry at Chiral Sulfur and Carbon Atoms Assigned Through an Original Combination of Spectroscopic and Computational Methods

Two new sulfoxide-containing metabolites, aplisulfamines A (1) and B (2), have been isolated from an Aplidium sp. collected in the Bay of Naples. Their planar structure and geometry of a double bond were readily determined by using standard methods, mainly NMR spectroscopy. An original approach was used to assign the absolute configuration at the three contiguous chiral centers present in the structures of both aplisulfamines, two at carbon and one at sulfur. This involved Electronic Circular Dichroism (ECD) studies, J-based configuration analysis and Density Functional Theory (DFT) calculations and represents an interesting integration of modern techniques in stereoanalysis, which could contribute to the enhancement of theoretical protocols recently applied to solve stereochemical aspects in structure elucidation

Zorrimidazolone, a Bioactive Alkaloid from the Non-Indigenous Mediterranean Stolidobranch Polyandrocarpa zorritensis

Chemical analysis of the Mediterranean ascidian Polyandrocarpa zorritensis (Van Name 1931) resulted in the isolation of a series of molecules including two monoindole alkaloids, 3-indolylglyoxylic acid (3) and its methyl ester (4), 4-hydroxy-3-methoxyphenylglyoxylic acid methyl ester (1) and a new alkaloid we named zorrimidazolone (2). The structure of the novel compound 2 has been elucidated by spectroscopic analysis and bioactivity of all compounds has been investigated. Zorrimidazolone (2) showed a modest cytotoxic activity against C6 rat glioma cell line

Electronic interactions in Dirac fluids visualized by nano-terahertz spacetime mapping

Ultraclean graphene at charge neutrality hosts a quantum critical Dirac fluid of interacting electrons and holes. Interactions profoundly affect the charge dynamics of graphene, which is encoded in the properties of its collective modes: surface plasmon polaritons (SPPs). The group velocity and lifetime of SPPs have a direct correspondence with the reactive and dissipative parts of the tera-Hertz (THz) conductivity of the Dirac fluid. We succeeded in tracking the propagation of SPPs over sub-micron distances at femto-second (fs) time scales. Our experiments uncovered prominent departures from the predictions of the conventional Fermi-liquid theory. The deviations are particularly strong when the densities of electrons and holes are approximately equal. Our imaging methodology can be used to probe the electromagnetics of quantum materials other than graphene in order to provide fs-scale diagnostics under near-equilibrium conditions

Long-Lived Phonon Polaritons in Hyperbolic Materials

Natural hyperbolic materials with dielectric permittivities of opposite signs along different principal axes can confine long-wavelength electromagnetic waves down to the nanoscale, well below the diffraction limit. Confined electromagnetic waves coupled to phonons in hyperbolic dielectrics including hexagonal boron nitride (hBN) and α-MoO3 are referred to as hyperbolic phonon polaritons (HPPs). HPP dissipation at ambient conditions is substantial, and its fundamental limits remain unexplored. Here, we exploit cryogenic nanoinfrared imaging to investigate propagating HPPs in isotopically pure hBN and naturally abundant α-MoO3 crystals. Close to liquid-nitrogen temperatures, losses for HPPs in isotopic hBN drop significantly, resulting in propagation lengths in excess of 8 μm, with lifetimes exceeding 5 ps, thereby surpassing prior reports on such highly confined polaritonic modes. Our nanoscale, temperature-dependent imaging reveals the relevance of acoustic phonons in HPP damping and will be instrumental in mitigating such losses for miniaturized mid-infrared technologies operating at liquid-nitrogen temperatures.Research at Columbia is supported by Vannevar Bush Faculty Fellowship ONR-VB: N00014-19-1-2630. We thank A. Sternbach and S. Zhang for helpful discussions. Exfoliation and transfer of hBN onto desired substrates and electron beam lithography of gold disks were performed by J.T.M. and supported by the National Science Foundation (DMR1904793). Additional structure fabrication was supported by the Center on Precision-Assembled Quantum Materials, funded through the U.S. National Science Foundation (NSF) Materials Research Science and Engineering Centers (award no. DMR-2011738). Initial simulations and experimental design from Vanderbilt were provided by J.D.C. in collaboration with the Columbia team (D.N.B. and G.N.) and was supported by the Office of Naval Research (N00014-18-1-2107). The hBN phonon band structure calculation was performed by R.C. and L.A. and supported by the Spanish MINECO/FEDER grant (MAT2015-71035- R). Cryogenics nano-optics experiments at Columbia were solely supported as part of Programmable Quantum Materials, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under award no. DE-SC0019443. D.N.B is the Gordon and Betty Moore Foundation’s EPiQS Initiative Investigator no. 9455.Peer reviewe

Polyaxibetaines A-C, three unique amino acids derivatives isolated from the marine sponge Axinella polypoides.

Betaines and similar zwitterionic compounds are widely distributed in terrestrial plants and algae, as well as in marine invertebrates. In biological systems, these highly soluble dipolar molecules serve as organic osmolytes (osmoprotectants), namely substances synthesized or taken up from the environment by cells for protection against osmotic stress. Osmoprotectants can stabilize proteins and membranes when salt levels or temperatures are unfavourable; therefore, they could play important roles in the adaption of cells of marine invertebrates to various adverse environmental conditions. Examples of betaines isolated from marine invertebrates are homarine,1 trigonelline,2 taurines, baikiain betaine,3 β-stachydrine, 4 nor- and aminozooanemonin, 5 pyridinebetaines A and B.5 Most of these compounds are amphoteric low-molecular weight quaternary ammonium compounds deriving from proteinogenic or non- proteinogenic amino acids in which the nitrogen atom if fully methylated. Within a recent investigation of alkaloids from Axinella sponges, we have examined specimens of Axinella polypoides collected along Sardinian coasts and we have isolated three novel unique compounds, polyaxibetaines A-C (1-3), whose structure elucidations are the subject of this paper.Polyaxibetaines A-C extend the structural variety of the so far known betaines; in compounds 1 and 2, indeed, the nitrogen atom of the -amino group of phenylalanine and tyrosine, respectively, is comprised in a piperidine ring and further methylated, while compound 3 is a pyridine derivative sharing the nitrogen atom with the alfa-amino group of a tyrosine residue

Conisulfamines A-C, novel unique alkyl sulfoxides from the Mediterranean ascidian Aplidium conicum

Ascidians belonging to the Aplidium genus are characterized by a great chemiodiversity that includes nitrogenous and non-nitrogenous metabolites, this latter group being dominated by prenyl quinones/hydroquinones, linear or cyclic derivatives1. These compounds are generally known as meroterpenes. Recently, we analyzed a sample of Aplidium conicum collected in the Bay of Naples and, surprisingly, the pattern of its secondary metabolites resulted very different from that of other samples of A. conicum previously investigated. In fact, the ascidian is completely lacking in meroterpenoids, whilst the main components of its methanolic extract are a new class of molecules, unsaturated linear alkylsulfoxides, whose major constituents are Conisulfamines A, B, and C. The structures of the new compounds have been elucidated through an extensive application of MS, 1H, 13C and 2D homo-and heteronuclear-NMR techniques. The stereochemical analysis of Conisulfamine A has been carried out in a three stages–approach, relying on the combination of NMR spectroscopy and computational methods

Polyaxibetaines A-C, three unique amino acids derivatives isolated from the marine sponge Axinella polypoides.

Betaines and similar zwitterionic compounds are widely distributed in terrestrial plants and algae, as well as in marine invertebrates. In biological systems, these highly soluble dipolar molecules serve as organic osmolytes (osmoprotectants), namely substances synthesized or taken up from the environment by cells for protection against osmotic stress. Osmoprotectants can stabilize proteins and membranes when salt levels or temperatures are unfavourable; therefore, they could play important roles in the adaption of cells of marine invertebrates to various adverse environmental conditions. Examples of betaines isolated from marine invertebrates are homarine,1 trigonelline,2 taurines, baikiain betaine,3 β-stachydrine, 4 nor- and aminozooanemonin, 5 pyridinebetaines A and B.5 Most of these compounds are amphoteric low-molecular weight quaternary ammonium compounds deriving from proteinogenic or non- proteinogenic amino acids in which the nitrogen atom if fully methylated. Within a recent investigation of alkaloids from Axinella sponges, we have examined specimens of Axinella polypoides collected along Sardinian coasts and we have isolated three novel unique compounds, polyaxibetaines A-C (1-3), whose structure elucidations are the subject of this paper.Polyaxibetaines A-C extend the structural variety of the so far known betaines; in compounds 1 and 2, indeed, the nitrogen atom of the -amino group of phenylalanine and tyrosine, respectively, is comprised in a piperidine ring and further methylated, while compound 3 is a pyridine derivative sharing the nitrogen atom with the alfa-amino group of a tyrosine residue