Comparison of phenolic content and antioxidant activity of Actaea racemosa L. and Actaea cordifolia DC

Actaea racemosa L. is used as a component of drugs or dietary supplements to alleviate the menopause symptoms. Its biological activity is associated with the presence of phenolic compounds. In our work, the analysis of isoflavones and phenolic acids – caffeic acid (CA), ferulic acid and isoferulic acid (iFA) – both free and bonded in two species of Actaea, was conducted using HPLC-PAD technique. Moreover, the antioxidant effect of extracts from different parts of the investigated plants was determined on the basis of DPPH assay. Significant variation of CA and iFA content was observed. The highest content of CA was found in A. racemosa, while Actaea cordifolia contained the highest amount of iFA. Isoflavones were not found in the investigated plants. The antioxidant activity assay showed the high free radical-scavenging ability of the extracts obtained from different parts of the plant.     

Factorizing matrices by Dirichlet multiplication

We show that nonsingular matrices factor into products of Dirichlet multipliers (defined in the article). In particular, this yields a decomposition of an arbitrary nonsingular matrix into a product of sparse matrices. In addition, we demonstrate how the factorizations at hand can be implemented numerically via efficient algorithms.     

Stability of a Runge-Kutta method for the Navier-Stokes equation

We investigate the linear stability properties of a Runge-Kutta method for the Navier-Stokes equations. The theoretical stability limit is compared with that encountered in numerical simulations of an initial-boundary value problem. Numerical results from simulation in 3D are presented.     

Polymerization of methyl 12-acryloxystearate,N,N-dimethyl 12-acryloxystearamide,and methyl 14-acryloxyeicosanoate

Several homopolymers and copolymers of the title compounds have been prepared by radical initiation with potassium persulfate or diethyl azobisisobutyrate. The copolymers exhibit a combination of the properties of the homopolymers of the monomers. The homopolymers are adhesive, very slightly elastic, and show cold flow. Several of the copolymers show possible promise for use as adhesives.     

Coumarin derivatives from Pedilanthus tithymaloides as inhibitors of conidial germination in Magnaporthe oryzae

In a screening for inhibitors of infection-related morphogenesis in the rice blast fungus Magnaporthe oryzae, a series of 10 coumarin derivatives were isolated from Pedilanthus tithymaloides (Euphorbiaceae). Seven of these compounds turned out to be known while three represent previously unreported natural products. Their structures were established on the basis of spectroscopic data and X-ray crystallography. Nine out of 10 coumarin derivatives were found to inhibit conidial germination in the phytopathogenic fungus at low concentrations.     

Global structure of a three-way junction in a phi29 packaging RNA dimer determined using site-directed spin labeling

The condensation of bacteriophage phi29 genomic DNA into its preformed procapsid requires the DNA packaging motor, which is the strongest known biological motor. The packaging motor is an intricate ring-shaped protein/RNA complex, and its function requires an RNA component called packaging RNA (pRNA). Current structural information on pRNA is limited, which hinders studies of motor function. Here, we used site-directed spin labeling to map the conformation of a pRNA three-way junction that bridges binding sites for the motor ATPase and the procapsid. The studies were carried out on a pRNA dimer, which is the simplest ring-shaped pRNA complex and serves as a functional intermediate during motor assembly. Using a nucleotide-independent labeling scheme, stable nitroxide radicals were attached to eight specific pRNA sites without perturbing RNA folding and dimer formation, and a total of 17 internitroxide distances spanning the three-way junction were measured using Double Electron-Electron Resonance spectroscopy. The measured distances, together with steric chemical constraints, were used to select 3662 viable three-way junction models from a pool of 65 billion. The results reveal a similar conformation among the viable models, with two of the helices (H(T) and H(L)) adopting an acute bend. This is in contrast to a recently reported pRNA tetramer crystal structure, in which H(T) and H(L) stack onto each other linearly. The studies establish a new method for mapping global structures of complex RNA molecules, and provide information on pRNA conformation that aids investigations of phi29 packaging motor and developments of pRNA-based nanomedicine and nanomaterial.     

Isolation, structure elucidation, and biological evaluation of the unusual heterodimer chrysoxanthone from the ascomycete IBWF11-95A

Chrysoxanthone, an unusual heterodimer of blennolide A and 2-hydroxychrysophanol linked through a diaryl ether bridge, was isolated from mycelia of the ascomycete IBWF11-95A grown in submerged culture. Its structure was elucidated by two-dimensional NMR spectroscopy. The metabolite shows antibacterial activity against different species with MIC values between 2.5 and 20 μg/mL while also inhibiting the growth of several fungi.