James K. Harper

Isopestacin, an isobenzofuranone from Pestalotiopsis microspora, possessing antifungal and antioxidant activities.

Isopestacin is an isobenzofuranone obtained from the endophytic fungus Pestalotiopsis microspora. While a few other isobenzofuranones are known from natural sources, isopestacin is the only one having a substituted benzene ring attached at the C-3 position of the furanone ring. The compound was isolated from culture broths of the fungus and crystallized and its structure was determined by X-ray crystallography. Both proton and carbon NMR spectral assignments are also reported for isopestacin. This compound possesses antifungal activity and, as measured by electron spin resonance specroscopy, it also behaves as an antioxidant scavenging both superoxide and hydroxy free radicals.

Pestacin: a 1,3-dihydro isobenzofuran from Pestalotiopsis microspora possessing antioxidant and antimycotic activities

Abstract Pestalotiopsis microspora, an endophytic fungus native to the rainforest of Papua New Guinea, produces a 1,3-dihydro isobenzofuran. This product, pestacin, is 1,5,7-trisubstituted and exhibits moderate antifungal properties and antioxidant activity 11 times greater than the vitamin E derivative trolox. Antioxidant activity is proposed to arise primarily via cleavage of an unusually reactive C–H bond and, to a lesser extent, through O–H abstraction. Isolation of pestacin was achieved by extraction of culture fluid with methylene chloride followed by silica gel chromatography. Structure was established by X-ray diffraction and 13C and 1H NMR. The X-ray data demonstrate that pestacin occurs naturally as a racemic mixture. A mechanism for post-biosynthetic racemization is proposed.

Ambuic acid, a highly functionalized cyclohexenone with antifungal activity from Pestalotiopsis spp. and Monochaetia sp.

Ambuic acid, a highly functionalized cyclohexenone, was isolated and characterized from Pestalotiopsis spp. and Monochaetia sp. these being biologically related endophytic fungi associated with many tropical plant species. This compound was found in representative isolates of these fungal species obtained from rainforest plants located on several continents. The relevance of ambuic acid to the biology of the association of these fungi to their host plants is also discussed.

Oocydin A, a chlorinated macrocyclic lactone with potent anti-oomycete activity from Serratia marcescens

A unique chlorinated macrocyclic lactone, termed oocydin A, was isolated from a strain of Serratia marcescens growing as an epiphyte on Rhyncholacis pedicillata, an aquatic plant native to the Carrao river of the Venezuelan-Guyanan region of South America. The lactone has a molecular mass of 470 Da, and contains one atom of chlorine, a carboxyl group and a tetrahydrofuran ring internal to a larger macrocyclic ring. MICs of approximately 0.03 microg ml(-1) were noted for oocydin A against such phytopathogenic oomycetes as Pythium ultimum, Phytophthora parasitica, Phytophthora cinnamomi and Phytophthora citrophora. With regard to the true fungi, oocydin A had either minimal or no effect against certain Fungi Imperfecti (including several pathogens of humans), two ascomycetes and a basidiomycete. Oocydin A may have potential as an antimycotic in agricultural applications and especially for crop protection.

Javanicin, an Antibacterial Naphthaquinone from an Endophytic Fungus of Neem, Chloridium sp.

The endophytic fungus Chloridium sp. produces javanicin under liquid and solid media culture conditions. This highly functionalized naphthaquinone exhibits strong antibacterial activity against Pseudomonas spp., representing pathogens to both humans and plants. The compound was crystallized and the structure was elucidated by X-ray crystallography. The X-ray structure confirms the previously elucidated structure of the compound that was done under standard spectroscopic methods. The importance of javanicin in establishing symbiosis between Chloridium sp. and its host plant, Azadirachta indica, is briefly discussed.

Flowering in males and females of a Utah willow, Salix regida and effects on growth, tannins, phenolic glycosides and sugars.

We manipulated resource allocation to reproduction in male and female Salix rigida by removing reproductive buds before expansion, and female flowers before fruit initiation. We documented a significant difference between fruiting and flowering females. Fruiting females produced smaller shoots, fewer reproductive buds and had lower concentrations of salicortin and tannins than females in the flower-removal treatment. No effect of treatment on growth and secondary metabolites was detected among males. Female controls produced less shoot biomass and fewer reproductive buds than male controls (...)

Mechanically Shaped Two-Dimensional Covalent Organic Frameworks Reveal Crystallographic Alignment and Fast Li-Ion Conductivity

Covalent organic frameworks (COFs) usually crystallize as insoluble powders, and their processing for suitable devices is thought to be limited. We demonstrate that COFs can be mechanically pressed into shaped objects having anisotropic ordering with preferred orientation between hk0 and 00l crystallographic planes. Five COFs with different functionality and symmetry exhibited similar crystallographic behavior and remarkable stability, indicating the generality of this processing. Pellets prepared from bulk COF powders impregnated with LiClO4 displayed room temperature conductivity up to 0.26 mS cm(-1) and high electrochemical stability. This outcome portends use of COFs as solid-state electrolytes in batteries.

A combined solid-state NMR and synchrotron X-ray diffraction powder study on the structure of the antioxidant (+)-catechin 4.5-hydrate.

Analyses combining X-ray powder diffraction (XRD) and solid-state NMR (SSNMR) data can now provide crystal structures in challenging powders that are inaccessible by traditional methods. The flavonoid catechin is an ideal candidate for these methods, as it has eluded crystallographic characterization despite extensive study. Catechin was first described nearly two centuries ago, and its powders exhibit numerous levels of hydration. Here, synchrotron XRD data provide all heavy-atom positions in (+)-catechin 4.5-hydrate and establish the space group as C2. SSNMR data ((13)C tensor and (1)H/(13)C correlation) complete the conformation by providing catechins five OH hydrogen orientations. Since 1903, this phase has been erroneously identified as a 4.0 hydrate, but XRD and density data establish that this discrepancy is due to the facile loss of the water molecule located at a Wyckoff special position in the unit cell. A final improvement to heavy-atom positions is provided by a geometry optimization of bond lengths and valence angles with XRD torsion angles held constant. The structural enhancement in this final structure is confirmed by the significantly improved fit of computed (13)C tensors to experimental data.

Functionalized para-substituted benzenes as 1,8-cineole production modulators in an endophytic Nodulisporium species.

A Nodulisporium species (designated Ti-13) was isolated as an endophyte from Cassia fistula. The fungus produces a spectrum of volatile organic compounds (VOCs) that includes ethanol, acetaldehyde and 1,8-cineole as major components. Initial observations of the fungal isolate suggested that reversible attenuation of the organism via removal from the host and successive transfers in pure culture resulted in a 50 % decrease in cineole production unrelated to an overall alteration in fungal growth. A compound (CPM1) was obtained from Betula pendula (silver birch) that increases the production of 1,8-cineole by an attenuated Ti-13 strain to its original level, as measured by a novel bioassay method employing a 1,8-cineole-sensitive fungus (Sclerotinia sclerotiorum). The host plant produces similar compounds possessing this activity. Bioactivity assays with structurally similar compounds such as ferulic acid and gallic acid suggested that the CPM1 does not act as a simple precursor to the biosynthesis of 1,8-cineole. NMR spectroscopy and HPLC-ES-MS indicated that the CPM1 is a para-substituted benzene with alkyl and carboxyl substituents. The VOCs of Ti-13, especially 1,8-cineole, have potential applications in the industrial, fuel and medical fields.

SOLID-STATE 13C CHEMICAL SHIFT TENSORS IN TERPENES. PART I. SPECTROSCOPIC METHODS AND CHEMICAL SHIFT STRUCTURE CORRELATIONS IN CARYOPHYLLENE OXIDE

Principal values of the 13C chemical shift tensor were obtained for the 15 carbons of solid caryophyllene oxide using an improved PHORMAT NMR analysis. The improvements include TIGER processing and improved proton decoupling. TIGER is an alternative to Fourier methods and shortens 2D data collection by incorporating information from a high‐resolution isotropic 1D FID to allow accurate processing of even severely truncated 2D evolution FIDs. In caryophyllene oxide, data collection required less than 1 day, giving significant time savings over comparable 2D Fourier methods. Experimental principal values were assigned with high statistical confidence to specific carbons by comparing them with corresponding calculated values. Correctly assigned values were used to evaluate five different tensor calculation methods. For caryophyllene oxide, the B3PW91 method gave the best correlation with experimental principal values with an RMS error of 2.3 ppm. Refinement of x‐ray positions for hydrogens was shown to improve the calculated RMS error by a factor of >2. Calculated tensors can be used to provide principal value orientations in the three methyl groups of caryophyllene oxide. One of the perpendicular component, δ⊥, is found to exhibit the largest shift variation and dominates the methyl shifts. Sterically unfavorable non‐bonded interactions between proximate hydrogens are shown to correlate with this large upfield shift in the δ⊥ component.