Phytochemical profiles, antioxidant and antimicrobial activity of Actinidia polygama and A. arguta fruits and leaves

Plants of two species of Actinidia genus grown in an adverse steppe climate were examined in terms of secondary metabolites’ accumulation, antioxidant potential, and antimicrobial ability. The aim of the work was to reveal whether the introduced plants A. arguta and A. polygama retain their well-known health benefits. Total content of polyphenols (549.2 and 428.1 mg GAE/100 g FW, respectively), flavonoids, and phenolic acids as well as total antioxidant activity and reducing power of the fruit isopropanol extracts were found to be equal or even higher than the reported data on kiwifruit varieties cultivated in China and other regions. Antioxidant potential and phenolic compounds’ content in the fruit peel of both species were higher when compared to pulp, while corresponding indices of leaves exceeded those of the fruit. Disc-diffusion assays showed low to moderate antibacterial activity of A. arguta and A. polygama fruit and leaf extracts against collection Gram-negative and Gram-positive strains. Clinical strains of P. aeruginosa and E. coli resistant to the action of ofloxacin were notably inhibited by A. arguta and A. polygama fruit and leaf crude extracts. Inhibiting effects of plant extracts on clinical strains of K. pneumoniae and A. baumannii were comparable with the effect of ofloxacin. GC-MS assays identified 23 and 36 chemical constituents, respectively in A. arguta and A. polygama fruit isopropanol extracts. The main compounds in both extracts were 2-propenoic acid, pentadecyl ester followed by squalene, 7,9-di-tert-butyl-1-oxaspiro(4,5)deca-6,9-dien-2,8-dione, octadecanoic acid, 2-oxo-methyl ester, ethyl-isoallocholate, and phytol having known bioactivities. Our findings confirmed the preservation of useful properties by the introduced plants and also indicated the rich health-promoting abilities and expedience of cultivating A. arguta and A. polygama in a steppe climate

Lattice and magnetic dynamics in polar chiral incommensurate antiferromagnet Ni2_2InSbO6_6

Complex systems with coexisting polarity, chirality and incommensurate magnetism are of great interest because they open new degrees of freedom in interaction between different subsystems and therefore they host a plethora of intriguing physical properties. Here we report on optical properties and lattice and spin dynamics of Ni$_2$InSbO$_6$ single crystals studied with the use of polarized optical microscopy and micro-Raman spectroscopy in the temperature range 10-300 K. Ni$_2$InSbO$_6$ crystallizes in a polar structure described by the noncentrosymmetric space group R3 and two types of structural domains were visualized due to natural optical activity of opposite chirality. Raman tensor elements of most A and E phonons along with their symmetry were determined. The manifestation of LO-TO splitting was observed for the A modes. By tracking the temperature dependencies of phonon frequencies the well pronounced spin-phonon interaction was observed for several modes below and above the N\'eel transition temperature TN = 76 K. In antiferromagnetic phase a wide excitation centred at 247 cm-1 was detected and assigned to the two-magnon mode and this value was used for estimating exchange parameters through linear spin-wave theory calculations.Comment: 10 pages, 7 figure

Soluble cuticular wax composition and antimicrobial activity of the fruits of Chaenomeles species and an interspecific hybrid

Plants of the genus Chaenomeles Lindl. (Rosaceae) naturally grow in Southeast Asia and represent the richest resource of biologically active compounds with beneficial properties for humans. Plants of C. japonica (Thunb.) Lindl. and C. speciosa (Sweet) Nakai species, and interspecific hybrid C. × superba (Frahm) Rehder (C. japonica × C. speciosa, Superba group) have been successfully introduced in the steppe zone of Ukraine and bear fruits. In this study, we evaluated chemical composition of fruit cuticular waxes and antimicrobial activity of fruit extracts. The soluble waxes were characterized using gas chromatography-mass spectrometry (GC-MS), and 26–36 compounds, representing 91.7–96.6% of the total soluble cuticular waxes, were identified. Waxes of Chaenomeles fruits belonged to six classes, namely fatty acids, alcohols, aldehydes, esters, ethers and alkanes. Aldehydes 7-hexadecenal and heptacosanal, and alkanes hexatriacontane and tetrapentacontane were the main constituents in the soluble cuticular waxes of C. speciosa and C. × superba fruits, accounting for more than half of the total contents. However, alkane tetrapentacontane, alcohol 8,10-hexadecadien-1-ol and heptacosanal prevailed in C. japonica fruit waxes. Isopropanolic fruit extracts exhibited dose-dependent antimicrobial activity against four Gram-negative bacteria, five Gram-positive bacteria and one fungal strain in the disc diffusion assay. In general, extracts from the Chaenomeles fruits demonstrated higher activity against Gram+ bacteria than Gram- strains. The strongest inhibiting activity was shown against Staphylococcus epidermidis (by the fruit extracts of C. × superba and C. speciosa), Micrococcus lysodeikticus and Candida albicans (both by C. × superba fruit extract). Results of the study confirmed accumulation of the bioactive compounds in the fruit waxes of different Chaenomeles species and antimicrobial ability of Chaenomeles fruits as well. These findings revealed the bioactive compounds in fruit cuticular waxes and suggested health-promoting properties of introduced Chaenomeles species

Structure and Stability of Two-Dimensional Complexes of C_20 Fullerenes

Two-dimensional complexes of C_20 fullerenes connected to each other by covalent bonds have been studied. Several isomers with different types of intercluster bonds have been revealed. The lifetimes of the (C_20)_MxM systems with M = 2 and 3 have been directly calculated at T = 1800 - 3300 K making use of molecular dynamics. It has been shown that these complexes lose their periodic cluster structure due to either coalescence of two fullerenes C_20 or decay of C_20 fullerenes. The activation energies of these processes exceed 2 eV.Comment: 17 pages, 5 figure

GIANT OPTICAL NONLINEARITY OF HETEROSTRUCTURES WITH InP SELF-ASSEMBLED QUANTUM DOTS

A nonlinear reection of the heterostructures with InP self-assembled quantumdots is studied by pump-probe technique. A saturation of pump-probe signal inthe spectral region of the absorption of quantum dots is found at extremely lowpump power density of about 1 W/cm2. This value together with estimation ofthe absorption coefficient leads to the conclusion that saturation of the nonlinearreection occurs when quantum dot absorbs only single quantum of the light. Thisis a real evidence of the giant optical nonlinearity of the quantum dots.24th International Conference on the Physics of Semiconductors : Jerusalem, Israel August 2-7, 199

FRANZ-KELDYSH OSCILLATIONS IN PUMP-PROBE SPECTRA OF InP SELF-ASSEMBLED QUANTUM DOTS

Heterostructures with InP self-assembled quantum dots were studied. StrongFranz-Keldysh oscillations were found in their nonlinear reection spectra mea-sured by pump-probe method. These oscillations manifest built-in electric field ofabout 30 kV/cm. We suppose that this field originates from electric charge cap-tured by the structural defects on the dots interface. An estimated areal densityof electric charge is about 2×1011cm-2.24th International Conference on the Physics of Semiconductors : Jerusalem, Israel August 2-7, 199

Nonlinearity-induced conformational instability and dynamics of biopolymers

We propose a simple phenomenological model for describing the conformational dynamics of biopolymers via the nonlinearity-induced buckling and collapse (i.e. coiling up) instabilities. Taking into account the coupling between the internal and mechanical degrees of freedom of a semiflexible biopolymer chain, we show that self-trapped internal excitations (such as amide-I vibrations in proteins, base-pair vibrations in DNA, or polarons in proteins) may produce the buckling and collapse instabilities of an initially straight chain. These instabilities remain latent in a straight infinitely long chain, because the bending of such a chain would require an infinite energy. However, they manifest themselves as soon as we consider more realistic cases and take into account a finite length of the chain. In this case the nonlinear localized modes may act as drivers giving impetus to the conformational dynamics of biopolymers. The buckling instability is responsible, in particular, for the large-amplitude localized bending waves which accompany the nonlinear modes propagating along the chain. In the case of the collapse instability, the chain folds into a compact three-dimensional coil. The viscous damping of the aqueous environment only slows down the folding of the chain, but does not stop it even for a large damping. We find that these effects are only weakly affected by the peculiarities of the interaction potentials, and thus they should be generic for different models of semiflexible chains carrying nonlinear localized excitations.Comment: 4 pages (RevTeX) with 5 figures (EPS

A Study of The Formation of Stationary Localized States Due to Nonlinear Impurities Using The Discrete Nonlinear Schr\"odinger Equation

The Discrete Nonlinear Schr$\ddot{o}$dinger Equation is used to study the formation of stationary localized states due to a single nonlinear impurity in a Caley tree and a dimeric nonlinear impurity in the one dimensional system. The rotational nonlinear impurity and the impurity of the form $-\chi \mid C \mid^{\sigma}$ where $\sigma$ is arbitrary and $\chi$ is the nonlinearity parameter are considered. Furthermore, $\mid C \mid$ represents the absolute value of the amplitude. Altogether four cases are studies. The usual Greens function approach and the ansatz approach are coherently blended to obtain phase diagrams showing regions of different number of states in the parameter space. Equations of critical lines separating various regions in phase diagrams are derived analytically. For the dimeric problem with the impurity $-\chi \mid C \mid^{\sigma}$, three values of $\mid \chi_{cr} \mid$, namely, $\mid \chi_{cr} \mid = 2$, at $\sigma = 0$ and $\mid \chi_{cr} \mid = 1$ and $\frac{8}{3}$ for $\sigma = 2$ are obtained. Last two values are lower than the existing values. Energy of the states as a function of parameters is also obtained. A model derivation for the impurities is presented. The implication of our results in relation to disordered systems comprising of nonlinear impurities and perfect sites is discussed.Comment: 10 figures available on reques