An anti-herpes simplex virus-type 1 agent from Xylaria mellisii (BCC 1005)

A structurally unique polyketide, mellisol (1) and 1,8-dihydroxynaphthol 1-O-α-glucopyranoside (3), were isolated from the fungus Xylaria mellisii (BCC 1005). The relative stereostructure of 1 was determined on the basis of X-ray crystallographic data. Compounds 1 and 3 exhibited activity against herpes simplex virus-type 1 with IC₅₀ values of 10.50 and 8.40 μg/mL, respectively. They also showed cytotoxic activity against vero cells at the concentration of 40-50 μg/mL.     

Antimalarial 20-membered macrolides from Streptomyces sp. BCC33756

Two new natural products, samroiyotmycins A (1) and B (2), along with two naturally new novclobiocin 101 (3) and 4-hydroxy-3-(3-methylbut-2-enyl)benzamide (5), and five known substances including neoantimycin, clorobiocin (4), 29-O-methylabierixin, daidzein, and 1-(3-indolyl)-2,3-dihydroxypropan-1-one have been isolated from Streptomyces sp. BCC33756. Their chemical structures were determined based on NMR spectral information and the relative stereochemistry of compound 1 was determined by X-ray crystallographic data. Both samroiyotmycins A and B exhibited antimalarial activity against Plasmodium falciparum K1—multi-drug resistant strain, with IC₅₀ values of 3.65 and 3.16 μg/mL, respectively. Compound 1 was inactive against both cancerous (MCF-7, KB) and non-cancerous (Vero) cells, while compound 2 displayed cytotoxicity against Vero cell with IC₅₀ value of 29.57 μg/mL.     

The unexpected role of pyridine-2-carboxylic acid in manganese based oxidation catalysis with pyridin-2-yl based ligands

A number of manganese-based catalysts employing ligands whose structures incorporate pyridyl groups have been reported previously to achieve both high turnover numbers and selectivity in the oxidation of alkenes and alcohols, using H(2)O(2) as terminal oxidant. Here we report our recent finding that these ligands decompose in situ to pyridine-2-carboxylic acid and its derivatives, in the presence of a manganese source, H(2)O(2) and a base. Importantly, the decomposition occurs prior to the onset of catalysed oxidation of organic substrates. It is found that the pyridine-2-carboxylic acid formed, together with a manganese source, provides for the observed catalytic activity. The degradation of this series of pyridyl ligands to pyridine-2-carboxylic acid under reaction conditions is demonstrated by (1)H NMR spectroscopy. In all cases the activity and selectivity of the manganese/pyridyl containing ligand systems are identical to that observed with the corresponding number of equivalents of pyridine-2-carboxylic acid; except that, when pyridine-2-carboxylic acid is used directly, a lag phase is not observed and the efficiency in terms of the number of equivalents of H(2)O(2) required decreases from 6-8 equiv. with the pyridin-2-yl based ligands to 1-1.5 equiv. with pyridine-2-carboxylic acid.     

Radiation resistances and decontamination of common pathogenic bacteria contaminated in white scar oyster (Crassostrea belcheri) in Thailand

In Thailand, white scar oyster (Crassostrea belcheri) was ranked for premium quality, being most expensive and of high demand. This oyster is often eaten raw, hence it may pose health hazards to consumers when contaminated with food-borne pathogens. As limited alternative methods are available to sterilize the oyster while preserving the raw characteristic, irradiation may be considered as an effective method for decontamination. In this study, the radiation resistance of pathogenic bacteria commonly contaminating the oyster and the optimum irradiation doses for sterilization of the most radiation resistant bacteria were investigated. The radiation decimal reduction doses (D₁₀) of Salmonella Weltevreden DMST 33380, Vibrio parahaemolyticus ATCC 17802 and Vibrio vulnificus DMST 5852 were determined in broth culture and inoculated oyster homogenate. The D₁₀ values of S. Weltevreden, V. parahaemolyticus and V. vulnificus in broth culture were 0.154, 0.132 and 0.059 kGy, while those of inoculated oyster homogenate were 0.330, 0.159 and 0.140 kGy, respectively. It was found that among the pathogens tested, S. Weltevreden was proved to be the most resistant species. An irradiation dose of 1.5 kGy reduced the counts of 10⁵ CFU/g S. Weltevreden inoculated in oyster meat to an undetectable level. The present study indicated that a low-dose irradiation can improve the microbial quality of oyster and further reduce the risks from the food-borne pathogens without adversely affecting the sensory attributes.     

Mild Oxidation of Alcohols with o‐Iodoxybenzoic Acid (IBX) in a Water/CH2Cl2 Mixture in the Presence of Phase‐Transfer Catalyst

A mild oxidation of alcohols to the respective carbonyl compounds with o‐iodoxybenzoic acid (IBX) catalyzed by n‐Bu₄NBr in a water/dichloromethane (1:1) mixture is described. The method offers the advantage of a simple, inexpensive catalyst and the diminution of organic solvent employed in the reaction.     

Torrubiellutins A-C, from insect pathogenic fungus Torrubiella luteorostrata BCC 12904

Investigation of the insect pathogenic fungus Torrubiella luteorostrata led to the isolation of three new macrocyclic torrubiellutins A-C (1-3) and the known pyrone diterpene 4. Structures were elucidated by spectroscopic data including 1D, 2D NMR, and MS spectral data. The absolute stereochemistry was determined by chemical means using Mosher reactions and Marfey's reagent, together with NOESY spectral data. Torrubiellutin C showed biological activities against KB, MCF-7, NCI-H187, and Vero cell lines with IC₅₀ varying from 0.78 to 4.36 μg/mL, while compound 4 exhibited antimalaria and anti-inflammatory activity with IC₅₀ values of 3.49 and 1.21 μg/mL, respectively.     

Pyridine stabilized oxiranyl remote anions

The chemistry of oxiranyl remote anions derived from α,β-epoxypyridines is investigated. Deprotonation of α,β-epoxy pyridines at the β-position and reactions of the corresponding anions with a variety of electrophiles are found to be highly regioselective, possibly as a consequence of stabilization from the chelation between lithium and the pyridine moiety in the form of a five-membered cyclic intermediate.     

Xanthones from the green branch of Garcinia dulcis

Two new prenylated xanthones, namely dulcisxanthone H and dulcisxanthone I along with garciniaxanthone C, were isolated from the dichloromethane extract of the green branch of Garcinia dulcis. Their structures were elucidated by the analysis of 1-D and 2-D NMR spectral data. Their antibacterial activities were also examined.     

Antimicrobial activity of cyathane derivatives from Cyathus subglobisporus BCC44381

Six unknown cyathane diterpenes, named cyathinins A – E, and 10-hydroxyerinacine S, were isolated from Cyathus subglobisporus BCC44381 along with six known compounds, striatoid C, striatin C, striatals A, C, D, and glochidone. The chemical structures were determined by means of high resolution mass spectrometry (HRESI-MS) and nuclear magnetic resonance (NMR) spectroscopy. The absolute configurations were confirmed by X-ray diffraction analysis. The isolated active compounds exhibited antimalarial against Plasmodium falciparum (IC₅₀ 0.88–7.51?μM), antibacterial activities against Mycobacterium tuberculosis (MIC 25–50?μg/mL), Gram-positive bacteria of Bacillus cereus and Enterococcus faecium (MIC 0.78–50?μg/mL) and Gram-negative bacteria of Escherichia coli, Acinetobacter baumannii and Klebsiella pneumoniae in a presence of phenylalanine-arginine β-naphthylamide (MIC 3.13–50?μg/mL), antifungal activity against Candida albicans (IC₅₀ 8.6–80.3?μM) activities, and cytotoxic activity against both cancerous (MCF-7, KB, NCI-H187, IC₅₀ 0.36–28.32?μM) and non-cancerous (Vero, IC₅₀ 0.13–91.50?μM) cells.