Anti-allergic principles of Rhinacanthus nasutus leaves

Three naphthoquinone derivatives, rhinacanthin-C (1), -D (2) and -N (3) were isolated from the extract of Rhinacanthus nasutus Kurz leaves and were tested for anti-allergic effect. The result indicated that all three compounds possessed very potent anti-allergic activity against antigen-induced β-hexosaminidase release as a marker of degranulation in RBL-2H3 cells with IC₅₀ values of 6.9, 8.9 and 6.4 μM, respectively. In addition, the effects of rhinacanthin-C, -D and -N on antigen-induced release of TNF-α and IL-4 were also examined. It was found that rhinacanthin-C showed the most potent on antigen-induced TNF-α release with an IC₅₀ value of 0.7 μM, followed by rhinacanthin-D (IC₅₀=3.8 μM) and rhinacanthin-N (IC₅₀=10.3 μM), whereas those for IL-4 were rhinacanthin-D (IC₅₀=5.4 μM), rhinacanthin-C (IC₅₀=7.0 μM) and rhinacanthin-N (IC₅₀=12.0 μM), respectively. The mechanisms in the late phase reaction of rhinacanthin-C, -D and -N were found to inhibit TNF-α and IL-4 gene expression in antigen-induced TNF-α and IL-4 releases on from RBL-2H3 cells as dose-dependent manners.The structure-activity trends of rhinacanthin-C,-D and-N on the inhibition of TNF-α release are as follow; substitution with octadienoic acid (rhinacanthin-C) conferred much higher activity than that of benzodioxo carboxylic acid ester (rhinacanthin-D) as well as naphthalene carboxylic acid ester (rhinacanthin-N). For the inhibition of IL-4 release, the substitution with octadienoic acid (rhinacanthin-C) and benzodioxo carboxylic acid ester (rhinacanthin-D) possessed the effect two-fold higher than that of naphthalene carboxylic acid ester (rhinacanthin-N).As regards active constituents for anti-allergic activity of R. nasutus, rhinacanthin-C, -D and -N are responsible for anti-allergic effect of this plant on both the early phase and late phase reactions. The finding may support the traditional use of R. nasutus leaves for treatment of allergy and allergy-related diseases.     

The Role for Glutamic Acid at Position 196 in Human Hypoxanthine Phosphoribosyltransferase (HPRT) as Investigated Using Site-Directed Mutagenesis

The crystal structure of human HPRT reveals the involvement of E196 side chain at the A-B dimer interface. Interference by valine substitution at this position (E196V), as identified in patients with Lesch-Nyhan disease, nearly abolishes enzymatic activity. Kinetic analysis of the active mutants (E196A, E196D, E196Q, and E196R) suggests that interaction between K68 and E196 side chains contributes to stabilization of cis-configuration during the catalytic cycle. The study also provides further insight into the role of A-B dimer interactions relating to K68 in the regulation of cis-trans isomerization that potentially governs the rate-limiting steps in the HPRT reaction.     

Identification of a product specific β-amyrin synthase from Arabidopsis thaliana

Triterpene skeletons are produced by oxidosqualene cyclases (OSCs). The genome sequencing of Arabidopsis thaliana revealed the presence of thirteen OSC homologous genes including At1g78950, which has been revised recently as two independent ORFs, namely At1g78950 and At1g78955. The cDNA corresponding to the revised At1g78950 was obtained by RT-PCR, ligated into Saccharomyces cerevisiae expression vector pYES2, and expressed in a lanosterol synthase deficient S. cerevisiae strain. LC-MS and NMR analyses of the accumulated product in the host cells showed that the product of At1g78950 is β-amyrin, indicating that At1g78950 encodes a β-amyrin synthase (EC 5.4.99.-).     

Prolonged inhibitory effects against planktonic growth,adherence, and biofilm formation of pathogens causing ventilator-associated pneumonia using a novel polyamide/silver nanoparticle composite-coated endotracheal tube

Abstract

Microbial cells can rapidly form biofilm on endotracheal tubes (ETT) causing ventilator-associated pneumonia, a serious complication in patients receiving mechanical ventilation. A novel polyamide with a good balance of hydrophilic/hydrophobic moieties was used for the embedment of green-reduction silver nanoparticles (AgNPs) for the composite-coated ETT. The films were conformal with a thickness of ～ 17?±?3?µm accommodating high loading of 60?±?35?nm spherical-shaped AgNPs. The coated ETT resulted in a significant difference in reducing both planktonic growth and microbial adhesion of single and mixed-species cultures, compared with uncoated ETT (p?<?0.05). A time-kill assay demonstrated rapid bactericidal effects of the coating on bacterial growth and cell adhesion to ETT surface. Biofilm formation by Pseudomonas aeruginosa and Staphylococcus aureus, commonly encountered pathogens, was inhibited by > 96% after incubation for 72?h. Polyamide/AgNP composite-coated ETT provided a broad-spectrum activity against both Gram-positive and Gram-negative bacteria as well as Candida albicans and prolonged antimicrobial activity.     

Dammarenediol-II synthase, the first dedicated enzyme for ginsenoside biosynthesis, in Panax ginseng

Panax ginseng produces triterpene saponins called ginsenosides, which are classified into two groups by the skeleton of aglycones, namely dammarane type and oleanane type. Dammarane-type ginsenosides dominate over oleanane type not only in amount but also in structural varieties. However, their sapogenin structure is restricted to two aglycones, protopanaxadiol and protopanaxatriol. So far, the genes encoding oxidosqualene cyclase (OSC) responsible for formation of dammarane skeleton have not been cloned, although OSC yielding oleanane skeleton (β-amyrin synthase) has been successfully cloned from this plant. In this study, cDNA cloning of OSC producing dammmarane triterpene was attempted from hairy root cultures of P. ginseng by homology based PCR method. A new OSC gene (named as PNA) obtained was expressed in a lanosterol synthase deficient (erg7) Saccharomyces cerevisiae strain GIL77. LC-MS and NMR analyses identified the accumulated product in the yeast transformant to be dammarenediol-II, demonstrating PNA to encode dammarenediol-II synthase.     

The role for glutamic acid at position 196 in human hypoxanthine phosphoribosyltransferase (HPRT) as investigated using site-directed mutagenesis

The crystal structure of human HPRT reveals the involvement of E196 side chain at the A-B dimer interface. Interference by valine substitution at this position (E196V), as identified in patients with Lesch-Nyhan disease, nearly abolishes enzymatic activity. Kinetic analysis of the active mutants (E196A, E196D, E196Q, and E196R) suggests that interaction between K68 and E196 side chains contributes to stabilization of cis-configuration during the catalytic cycle. The study also provides further insight into the role of A-B dimer interactions relating to K68 in the regulation of cis-trans isomerization that potentially governs the rate-limiting steps in the HPRT reaction.     

Co-occurrence of five Fusarium toxins in corn-Dried Distiller’s Grains with Solubles in Thailand and comparison of ELISA and LC-MS/MS for fumonisin analysis

Dried Distiller’s Grains with Solubles (DDGS), a by-product of bio-ethanol production from maize and other cereals, is increasingly used as a feed additive. In this study, five Fusarium toxins, including fumonisin B₁ (FB₁), fumonisin B₂ (FB₂), deoxynivalenol (DON), zearalenone (ZEN) and beauvericin (BEA) were quantified by LC-MS/MS in 59 corn-DDGS samples. In addition, the fumonisin level in 30 randomly selected-samples was compared using an ELISA detection technique. No sample was free from mycotoxin contamination, and 50.8 % of the samples were co-contaminated with all five mycotoxins. Moreover, toxin levels were generally high, with mean levels of 9 mg kg^?1 FB₁, 6 mg kg^?1 FB₂, 1.2 mg kg^?1 DON, 0.9 mg kg^?1 ZEN, and 0.35 mg kg^?1 BEA. Maximum levels for FB₁ (143 mg kg^?1) and FB₂ (125 mg kg^?1) are of acute toxicological relevance. The ELISA method had a tendency to underestimate the fumonisin content when compared with LC-MS/MS. Finally, this is the first reported beauvericin contamination in corn-DDGS.     

Keys to success for a school-based malaria control program in primary schools in Thailand

School-based malaria control has been recognized as a new approach for the control of this disease in the Greater Mekong Subregion since 2000. We evaluated a school-based malaria control program near the western border of Thailand using a before-after intervention study. The major intervention activities included teacher training with specialized malaria teaching materials and participatory learning methods. The target population was 17 school principals, 111 teachers and 852 schoolchildren of grade 3, 4, and 5 in 17 schools. After the intervention, the teachers taught about malaria more actively than before. The teachers who could design a lesson plan on malaria increased from 30.7% to 47.7% (p=0.015) and the teachers who had taught about malaria increased from 71.9% to 84.3% (p=0.035). As a result of the program, the schoolchildren changed their behavior positively towards malaria prevention with significant difference in 6 of 7 questions. For example, the schoolchildren 'who always took care of mosquito bites' increased from 42.7% to 62.1% (p<0.001) and the schoolchildren 'who always reported their parents or teachers when they had fever' increased from 36.0% to 56.0% (p<0.001). In conclusion, the keys to a successful intervention lie in good teaching materials and a participatory approach utilizing the well-established Thailand's school health system. Beyond Thailand, school-based malaria control could be applied to other Greater Mekong Subregion countries with careful analysis of school health context in each country.