Betty C. R. Zhu

Evaluation of Vetiver Oil and Seven Insect-Active Essential Oils Against the Formosan Subterranean Termite

Repellency and toxicity of 8 essential oils (vetiver grass, cassia leaf, clove bud, cedarwood, Eucalyptus globules,Eucalyptus citrodora, lemongrass and geranium) were evaluated against the Formosan subterranean termite, Coptotermes formosanus Shiraki. Vetiver oil proved the most effective repellent because of its long-lasting activity. Clove bud was the most toxic, killing 100% of termites in 2 days at 50 μg/cm2. The tunneling response of termites to vetiver oil also was examined. Vetiver oil decreased termite tunneling activity at concentrations as low as 5 μg/g sand. Tunneling and paper consumption were not observed when vetiver oil concentrations were higher than 25 μg/g sand. Bioactivity of the 8 oils against termites and chemical volatility were inversely associated. Listed in decreasing order of volatility, the major constituents of the 8 oils were: eucalyptol, citronellal, citral, citronellol, cinnamaldehyde, eugenol, thujopsene, and both α- and β- vetivone. Vetiver oil is a promising novel termiticide with reduced environmental impact for use against subterranean termites.

Nootkatone is a repellent for Formosan subterranean termite (Coptotermes formosanus).

We examined the behavior of Formosan subterranean termites toward one of the components of vetiver grass oil, the roots of which manufacture insect repellents. We found nootkatone, a sesquiterpene ketone, isolated from vetiver oil is a strong repellent and toxicant to Formosan subterranean termites. The lowest effective concentration tested was 10 μg/g substrate. This is the first report of nootkatone being a repellent to insects.

Structure-activity of valencenoid derivatives and their repellence to the Formosan subterranean termite

Eight valencenoid derivatives were evaluated for their repelling activity against Formosan subterranean termites, Coptotermes formosanus Shiraki. Among them, 1,10-dihydronootkatone was the strongest repellent, and valencene was the weakest. Results of the structure–repellency relationships indicated (1) reduction of the ketone group to the alcohol on position 2 of nootkatone curtailed the activity; (2) because of the low activity of valencene relative to nootkatone that the ketone group was essential for repellent activity; (3) reduction of the 1,10 double bond (1,10-dihydronootkatone and tetrahydronootkatone) produced compounds more repellent than nootkatone; (4) the isopropenyl group probably does not participate in binding as evidenced by no significant difference in the repellent activity among nootkatone (double bond between position 11 and 12), isonootkatone (double bond between position 7 and 11), and 11,12-dihydronootkatone.

Chitovibrin: a chitin-binding lectin fromVibrio parahemolyticus

A novel 134 kDa, calcium-independent chitin-binding lectin, ‘chitovibrin’, is secreted by the marine bacteriumVibrio parahemolyticus, inducible with chitin or chitin-oligomers. Chitovibrin shows no apparent enzymatic activity but exhibits a strong affinity for chitin and chito-oligomers >dp9. The protein has an isoelectric pH of 3.6, shows thermal tolerance, binds chitin with an optimum at pH 6 and is active in 0–4m NaCl. Chitovibrin appears to be completely different from other reported Vibrio lectins and may function to bindV. parahemolyticus to chitin substrates, or to capture or sequester chito-oligomers. It may be a member of a large group of recently described proteins in Vibrios related to a complex chitinoclastic (chitinivorous) system.

Structural requirements for repellency: norsesquiterpenes and sesquiterpenoid derivatives of nootkatone against the Formosan subterranean termite (Isoptera: Rhinotermitidae).

BACKGROUND Research has shown that the family of grapefruit flavors called nootkatones have significant repellant and toxic effects to Formosan subterranean termites (Coptotermes formosanus Shiraki). RESULTS Nineteen synthetic nootkatone derivatives, along with three commercially available nootkatone derivatives, were tested for repellent activity against C. formosanus by a choice assay in a petri dish with a two-step triage procedure. Based on the repellency threshold value, the relationships between structure and activity are discussed. CONCLUSION Four derivatives of nootkatone have very high repellency and toxicity to C. formosanus, 9 times the potency of the primary compound nootkatone. Four other compounds have between 2 and 3 times the repellency of nootkatones, and three compounds are equal in their repellency to nootkatone.

Purification of acetyllactosamine-specific tomato lectin by erythroglycan-sepharose affinity chromatography.

Tomato lectin is specific for oligomers of poly-N-acetyllactosamine containing 3 repeating Gal(beta 1-4)GlcNAc (beta 1-3)-disaccharides. As such it is highly useful for purifying oligosaccharides or glycopeptides with poly-N-acetyllactosamine character. We have found the lectin very useful as an affinity reagent for isolating glycoproteins or glycoprotein domains having poly-N-acetyllactosamine glycosylation. Conventional preparation of tomato lectin by ovomucoid-Sepharose affinity chromatography was found to be unsatisfactory due to instability of column and bleeding of ovomucoid into eluents requiring the necessity for additional purification steps following affinity chromatography. We prepared a column of human erythrocyte band 3 carbohydrate glycopeptide (erythroglycan) attached to Sepharose as an affinity matrix. The purification of tomato lectin to homogeneity in one step on this column matrix is described in this report.

The sesquiterpenoid nootkatone and the absolute configuration of a dibromo derivative.

Nootkatone, or (4R,4aS,6R)-4,4a,5,6,7,8-hexahydro-4,4a-dimethyl-6-(1-methylethenyl)naphthalen-2(3H)-one, C(15)H(22)O, a sesquiterpene with strong repellent properties against Formosan subterranean termites and other insects, has the valencene skeleton. The dibromo derivative (1S,3R,4S,4aS,6R,8aR)-1,3-dibromo-6-isopropyl-4,4a-dimethyl-1,2,3,4,5,6,7,8-octahydronaphthalen-2-one, C(15)H(24)Br(2)O, has two independent molecules in the asymmetric unit, which differ in the rotation of the isopropyl group with respect to the main skeleton. The C-Br distances are in the range 1.950 (4)-1.960 (4) A. Both independent molecules form zigzag chains, with very short intermolecular carbonyl-carbonyl interactions, having the perpendicular motif and O...C distances of 2.886 (6) and 2.898 (6) A. These chains are flanked by intermolecular Br...Br interactions of distances in the range 4.067 (1)-4.218 (1) A. The absolute configuration of the dibromo derivative was determined, from which that of nootkatone was inferred.

Catalytically Inactive Endoglycosidases as Microbial Diagnostic Reagents: Chitinases and Lysozymes as Fungal and Bacterial Capture/Label Agents

Publisher Summary Catalytically disabled forms of enzymes have been used as carbohydrate recognition and detection systems. Such mutated enzymes have been developed for detection of bacterial infections and fungal infections. Such enzymes have low turnover number rendering them “catalytically inactive” in the time frame of the observation event. Therefore endoglycosidases employed as fungal or bacterial detection systems in a “catalytically inactive mode,” utilize only their binding specificity. The use of cell wall polymer degradative enzymes as targeted diagnostic agents has several advantages such as high specificity for the target polymer, high avidity, much more economical than antibodies, and no nonspecific binding in human tissues. Catalytically inactive enzymes constitute a new class of capture/label reagents useful in the several types of assays, including slide-based stains, fluorescence, ELISA (enzyme-linked immunosorbent assay), dipsticks, latex agglutination assays, skin disclosure stains (skin, nail fungi, onchyomycosis), flow cytometry (for bacteria or yeast forms of fungi), and surface plasmon resonance.

Terpene-lnduced Morphological Changes to Exoskeleton of Formosan Subterranean Termites (Isoptera: Rhinotermitidae): Toxic Effects of cis-nerol

The terpenoid, cis-nerol was found to be highly toxic to the Formosan subterranean termite, Coptotermes formosanus Shiraki. Morphological abnormalities were observed in the exoskeleton including th...