Isolation of the volatile oil from Satureja thymbra by supercritical carbon dioxide extraction: chemical composition and biological activity

Satureja thymbra L. is well known in Italy by the popular name of "Santoreggia sarda". It grows only in Sardinia and nowadays it is restricted to the slope of the Colle San Michele in Cagliari. The composition of the aromatic extracts obtained by supercritical CO2 and by hydrodistillation and their antifungal activity is reported. The collected extracts were analyzed by GC-FID and GC-MS methods. No significant differences were observed in the composition of the volatile extracts depending on the extraction method. The results showed the presence of thymol, gamma-terpinene, beta-caryophyllene, p-cymene, carvacrol and borneol as main components. The minimal inhibitory concentration (MIC) and the minimal lethal concentration (MLC) were used to evaluate the antifungal activity of the oils against Candida albicans, C. tropicalis, C. krusei, C. guillermondii, C. parapsilosis, Cryptococcus neoformans, Trichophyton rubrum, T. mentagrophytes, T. mentagrophytes var. interdigitale, Trichophyton rubrum, T. verrucosum, Microsporum canis, M. gypseum, Epidermophyton floccosum, Aspergillus niger, A. fumigatus and A. flavus. The volatile extracts revealed a wide-spectrum antifungal activity. They were fungicidal and similarly potent against yeasts, dermatophyte and Aspergillus stains, with MICs ranging from 0.16 to 0.32 pL x mL(-1).     

Plant Oil Bodies: Novel Carriers to Deliver Lipophilic Molecules

Oil bodies (OBs) are specialised organelles ubiquitously detected in plant oil seeds, which serve as lipid storage compartments. OBs consist of a hydrophobic core of triacylglycerol (TAGs), surrounded by a monolayer of phospholipids (PLs) embedded with some specific proteins with a size ranging from 0.5 to 2 μm. In this work, we report an easy method to reconstitute OBs starting from their constituents and to encapsulate lipophilic molecules, i.e. the fluorescent fluorescein isothiocyanate (FITC) and carboxyfluorescein (CF), into reconstituted OBs. This methods allowed us to produce OBs 4- to 10-fold smaller (50–200 nm) than the native one and to obtain a good recovery (about 40%) of both the fluorescent compounds used in the present work. The properties of reconstituted OBs were investigated by a combination of Brewster angle microscopy, scanning force microscopy, ζ-potential techniques. OBs were stable and formed ordered monolayers when patterned on hydrophobic substrates whereas they showed a higher tendency to aggregate into larger, coalescing OBs when were deposited onto hydrophilic substrates or at the air/water interface. Furthermore, we verified the uptake of FITC-loaded OBs by the MCF-7 breast cancer cell line. Our results indicated that OBs could be envisaged as novel carriers to deliver hydrophobic bioactive compounds.     

Ideals Generated by Diagonal 2-Minors

With a simple graph G on [n], we associate a binomial ideal P_G generated by diagonal minors of an n × n matrix X = (x_ij) of variables. We show that for any graph G, P_G is a prime complete intersection ideal and determine the divisor class group of K[X]/P_G. By using these ideals, one may find a normal domain with free divisor class group of any given rank.     

Copula-based measures of dependence structure in assets returns

Copula modeling has become an increasingly popular tool in finance to model assets returns dependency. In essence, copulas enable us to extract the dependence structure from the joint distribution function of a set of random variables and, at the same time, to isolate such dependence structure from the univariate marginal behavior. In this study, based on US stock data, we illustrate how tail-dependency tests may be misleading as a tool to select a copula that closely mimics the dependency structure of the data. This problem becomes more severe when the data is scaled by conditional volatility and/or filtered out for serial correlation. The discussion is complemented, under more general settings, with Monte Carlo simulations and portfolio management implications.     

A postcard from the past: The behavior of U.S. stock markets during 1871-1938

In this article, we study the behavior of the stock prices of a subset of eight U.S. industries from the late 1800's to the Great Depression. In particular, we focus on the potential presence of volatility shifts, the persistence of volatility, and on the degree of co-movement of stock returns prior to and during the Great Depression. Our findings show that stock markets became particularly volatile toward the mid 1930's, but that the persistence of volatility tended to decrease around the same time period. In that regard, we find little evidence that such behavior is driven by trading volume. In addition, we conclude that the overall correlation across the different industries was relatively more significant in statistical terms from 1921 to part of the Great Depression (1929-1931; 1933-1934 and 1936).     

Effects of anisotropy on the free convection from a vertical plate embedded in a porous medium

The effects of anisotropy on the steady laminar boundary-layer free convection over a vertical impermeable surface are analysed by using the method of integral relations. If the permeability in the direction orthogonal to the plate is greater than the permeability along the plate, then there is an increase in the temperature field.