David Weisleder

A nematicidal toxin fromPleurotus ostreatus NRRL 3526

A nematicidal toxin was purified fromPleurotus ostreatus NRRL 3526 grown on moistened, autoclaved wheat straw for 30 days at room temperature (21–33°C). The active compound, at a concentration of 300 ppm, immobilized 95% of test nematodes (Panagrellus redivivus) within 1 hr. Immobilized nematodes did not recover, even after being rinsed with deionized water. The toxin was identified astrans-2-decenedioic acid.

A new fumonisin from solid cultures of Fusarium moniliforme

A new fumonisin has been isolated from Fusarium moniliforme isolate MRC826 grown on corn. It was shown by NMR and mass spectrometry to be an isomer of fumonisin B2 that has free hydroxyl groups at C-3 and C-10 instead of the normal C-3 and C-5. This new fumonisin was detected in cultures of most isolates of F. moniliforme that were examined and was usually present at concentrations similar to those of fumonisin B2. Two isolates of F. moniliforme that produce significantly higher levels of this new isomer were identified.

A facile synthesis of 4-hydroxy-2(E)-nonenal

A facile, efficient synthesis of 4-hydroxy-2(E)-nonenal is presented as an alternative to the approaches published previously, which either employed four to six separate steps or furnished low yields. The commercially available 3(Z)-nonenol was sequentially oxidized into 3,4-epoxynonanol by 3-chloroperoxybenzoic acid followed by oxidation of the alcohol by periodinane to afford 4-hydroxy-2(E)-nonenal by this two-step procedure in 48±7% yield.

Male-specific sesquiterpenes from Phyllotreta and Aphthona flea beetles

It was previously reported that males of the crucifer flea beetle, Phyllotreta cruciferae, feeding on host foliage are attractive to both males and females in the field. Based on this evidence for an aggregation pheromone, volatiles were collected from male and female P. cruciferae feeding on cabbage (Brassica oleracea) and analyzed. For comparison, volatiles were also collected from males and females of three other flea beetle species, Aphthona flava,A. czwalinae, and A. cyparissiae, all feeding on their host, leafy spurge foliage (Euphorbia esula). Six male-specific compounds were isolated from P. cruciferae, and the same compounds plus two additional ones were isolated from males of Aphthona flava,A. czwalinae, and A. cyparissiae. The blends of compounds were relatively consistent within species, but there were characteristic differences between species. Compound structures were studied by mass spectrometry, NMR spectroscopy, UV spectroscopy, polarimetry, chiral and achiral gas chromatography, molecular modeling, and microchemical tests. Three of the compounds were identified as (+)-ar-himachalene; (+)-trans-α-himachalene; (+)-γ-cadinene. Two others were new enantiomers of himachalene hydrocarbons that were previously identified from the fir trees, Abies alba and Abies nordmanniana. Finally, there were two himachalene alcohols and one norsesquiterpene ketone that is a himachalene analog. Only (+)-ar-himachalene and (+)-γ-cadinene are previously known natural products. Electrophysiological activity was demonstrated for five of the compounds. The chemical and electrophysiological patterns are consistent with, but do not prove, a pheromonal function.

Substrate specificity of acetylxylan esterase from Schizophyllum commune: mode of action on acetylated carbohydrates

Substrate specificity of a purified acetylxylan esterase from Schizophyllum commune was investigated on a variety of methyl per-O-acetyl glycopyranosides, methyl di-O-acetyl-beta-D-xylopyranosides and acetylated polysaccharides. The enzyme preferentially deacetylated the 3-position of methyl 2,3,4-tri-O-acetyl-beta-D-xylopyranoside and 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside. Removal of the 3-acetyl group from the xylopyranoside was accompanied by a slower deacetylation at positions 2 and 4. A similarly slower, accompanying deacetylation occurred primarily at position 2 with the glucopyranoside. Such specificity corresponds well to the expected function of the esterase in acetylxylan degradation. Of the three possible diacetates of methyl beta-D-xylopyranoside, the 3,4-diacetate was found to be the most rapidly deacetylated. Unexpectedly, products of its deacetylation were a mixture of 2- and 4-monoacetate. The formation of the methyl 2-O-acetyl-beta-D-xylopyranoside involved an enzyme-mediated acetyl group transfer because the rate of the enzyme-catalyzed reaction exceeded the rate of spontaneous migration of acetyl groups. This is the likely mechanism for acetyl removal from position 2 in the native substrate. The enzyme exhibited the highest regioselectivity with methyl 2,3,4,6-tetra-O-acetyl-beta-D-mannopyranoside. An 80% conversion of this substrate to methyl 4,6-di-O-acetyl-beta-D-mannopyranoside, a new mannose derivative, was achieved. In contrast to the majority of lipases and esterases exploited for regioselective deacetylation, the S. commune acetylxylan esterase did not attack the C-6 acetyl linkages in methyl hexopyranosides when other acetyl groups were available.

Synthesis and characteristics of polyhydroxy triglycerides from milkweed oil

The milkweed family Asclepiadaceae comprises many genera including the genus Asclepias syriaca, otherwise known as the common milkweed. This plant had been considered a nuisance and serious efforts made toward its eradication. However, milkweed has become an industrial crop of growing significance on account of market demand for its hypoallergenic floss in pillows, comforters and other industrial uses. Processing of milkweed pods gives three product streams of floss, seed and pod hulls. The seed contains about 25% by weight of very highly unsaturated oil with some unusual fatty acids. The objective of this study was to generate value-added products from milkweed oil. To achieve this, the triglycerides of A. syriaca seed were oxidized to the polyoxirane and polyhydroxy triglyceride derivatives by means of an in situ peroxy acid method. The epoxy triglycerides produced exhibited high stability and highly viscous behavior, whereas the polyhydroxy triglycerides showed additional unusually stable emulsifying properties for oil in water emulsions.

Biofumigant compounds released by field pennycress (Thlaspi arvense) seedmeal.

Defatted field pennycress (Thlaspi arvense L.) seedmeal was found to completely inhibit seedling germination/emergence when added to a sandy loam soil containing wheat (Triticum aestivum L.) and arugula [Eruca vesicaria (L.) Cav. subsp. sativa (Mill.) Thell.] seeds at levels of 1.0% w/w or higher. Covering the pots with Petri dishes containing the soil-seedmeal mixture decreased germination of both species at the lowest application rate (0.5% w/w), suggesting that the some of the phytotoxins were volatile. CH2Cl2, MeOH, and water extracts of the wetted seedmeal were bioassayed against wheat and sicklepod (Senna obtusifolia (L.) H. S. Irwin & Barneby) radicle elongation. Only the CH2Cl2 extract was strongly inhibitory to both species. Fractionation of the CH2Cl2 extract yielded two major phytotoxins, identified by gas chromatography–mass spectrometry and NMR as 2-propen-1-yl (allyl) isothiocyanate (AITC) and allyl thiocyanate (ATC), which constituted 80.9 and 18.8%, respectively, of the active fraction. When seeds of wheat, arugula and sicklepod were exposed to volatilized AITC and ATC, germination of all three species was completely inhibited by both compounds at concentrations of 5 ppm or less. In field studies, where seedmeal was applied at 0.50, 1.25, and 2.50 kg/m2 and tarped with black plastic mulch, all of the treatments significantly reduced dry weight of bioassay plants compared to the tarped control, with the highest seedmeal rate decreasing dry matter to less than 10% of the control 30 d after seedmeal application. Field pennycress seedmeal appears to offer excellent potential as a biofumigant for high-value horticultural crops for both conventional and organic growers.

Hydroxy fatty acids through hydroxylation of oleic acid with selenium dioxide/tert.-butylhydroperoxide

Oleic acid was hydroxylated in the allylic positions with the selenium dioxide/tert.-butylhydroperoxide system to give 8-hydroxy-9(E)-octadecenoic acid, 11-hydroxy-9(E)-octadecenoic acid and the novel 8,11-dihydroxy-9(E)-octadecenoic acid. This is a viable method for obtaining hydroxy fatty acids. The unsaturated hydroxy acids were hydrogenated with the hydrazine/air system to give the cor-responding saturated products. 8,11-Dihydroxyoctadecanoic acid thus obtained is also a novel compound. The saturated and unsaturated dihydroxy products were obtained aserythro/threo isomers as determined by nuclear magnetic resonance.

Male-specific tetraene and triene hydrocarbons ofCarpophilus hemipterus: Structure and pheromonal activity

Males ofCarpophilus hemipterus (L.), the dried-fruit beetle, (Coleoptera: Nitidulidae) were found to emit nine all-E tetraene and one all-E triene hydrocarbons in addition to two pheromonally active tetraenes that had been reported previously. The previously known compounds are (2E,4E,6E,8E)-3,5,7-trimethyl-2,4,6,8-decatetraene(1) and (2E,4E,6E,8E)-3, 5,7-trimethyl-2,4,6,8-undecatetraene(2). The new tetraenes were all related to structure1 by having one additional carbon at either one or two of the following four locations: at carbon 1 of the chain, at carbon 10 of the chain, at the 5-alkyl branch, or at the 7-alkyl branch. (Structure 2 also fits within this pattern.) The triene inC. hemipterus is (2E,4E,6E)-5-ethyl-3-methyl-2, 4,6-nonatriene. Also identified from volatile collections from the beetles were the 2Z and 4Z isomers of1. All structures were proven by synthesis, with NMR and mass spectral data for the compounds provided. Two of the newly discovered compounds, (2E,4E,6E,8E)-7-ethyl-3,5-dimethyl-2,4,6,8-decatetraene and (2E,4E,6E,8E)-7-ethyl-3,5-dimethyl-2,4,6,8-undecatetraene, were quite active in the wind-tunnel bioassay, but others, such as (2E,4E,6E,8E)-5-ethyl-3,7-dimethyl-2,4,6,8-decatetraene and (2E,4E,6E,8E)-4,6,8-trimethyl-2,4,6,8-undecatetraene were not. Structureactivity relationships are explored among the natural compounds and additional, synthetic analogs, which were never detected from the beetles. Some of these analogs, such as (2E,4E,6E,8E)-3,5-dimethyl-7-propyl-2,4,6,8-undecatetraene, were quite active in the bioassay. The biosynthesis of the beetle-derived compounds is discussed. A single biosynthetic scheme that lacks complete enzyme specificity at four specific steps could account for the entire series of compounds found in the beetles and their relative proportions. The definition of “pheromone” is discussed in relation to these hydrocarbons.

Microbial production of a novel trihydroxy unsaturated fatty acid from linoleic acid

A bacterium isolated from a dry soil sample collected from McCalla, AL, USA, converted linoleic acid to a novel compound, 12,13,17-trihydroxy-9 (Z)-octadecenoic acid (THOA). The organism is a Gram-positive, non-motile rod (0.5 μ m × 2 μ m). It was identified as a species of Clavibacter ALA2. The product was purified by high pressure liquid chromatography, and its structure was determined by 1H and 13C nuclear magnetic resonance and Fourier transform infrared spectroscopies, and by mass spectrometer. Maximum production of THOA with 25% conversion of the substrate was reached after 5–6 days of reaction. THOA was not further metabolized by strain ALA2. This is the first report of a 12,13,17-trihydroxy unsaturated fatty acid and its production by microbial transformation. Some dihydroxy intermediates were also detected. THOA has a structure similar to those of known plant self-defense substances.