Shuhei Nakajima

Tonically immobilized selfish prey can survive by sacrificing others

Death-feigning, also called tonic immobility, is found in a number of animal species across vertebrate and invertebrate taxa. To date, five hypotheses have been proposed for the adaptive significance of tonic immobility. These are that tonic immobility is effective for prey because (i) avoiding dead prey is safer for predators, (ii) immobility plays a role in physical defence, (iii) immobility plays a role in concealment and/or background matching, (iv) predators lose interest in unmoving prey, and (v) the characteristic immobilization posture signals a bad taste to predators. The fourth and fifth hypotheses have been considered suitable explanations for tonic immobility of the red flour beetle against its predator, the jumping spider. In the present study, we used chemical analyses of secretions by the red flour beetles under attack by the jumping spider to reject the fifth hypothesis for this system. More importantly, we tested a selfish-prey hypothesis for the adaptive significance of death-feigning as an anti-predator strategy, in which individuals adopting tonic immobility survive by sacrificing neighbours. Findings showed that survival rates of feigners were higher when in the presence of non-feigners or prey of a different species, compared to when alone, thus confirming our selfish-prey hypothesis. In summary, our results suggest that immobility following a spider attack is selfish; death-feigning prey increase their probability of survival at the expense of more mobile neighbours.

Different behavior of artemisinin and tetraoxane in the oxidative degradation of phospholipid

The reaction of trioxane and tetraoxane endoperoxides with unsaturated phospholipid 1 in the presence of Fe(II) was investigated in the absence of oxygen by means of tandem ESI-MS analysis. The spectral analyses for the reaction mixtures showed that artemisinin 2 with a trioxane structure gave no peak except that for the remaining intact phospholipid 1 (m/z 758.9), indicating that there was no structural change to 1. On other hand, the reaction mixture of 1 with tetraoxanes 3 and 4 afforded a number of new peaks (m/z 620-850) that were presumably assigned to oxidative degradation products originating from phospholipid 1. Since this reaction was completely inhibited by the addition of a phenolic antioxidant, the process was considered to involve some free radical species. The newly discovered marked differences in reactivity between the trioxane and the tetraoxanes possibly reflects their different anti-malarial mechanisms, and this reactivity may contribute to the classification of a number of anti-malarial endoperoxides whose mode of action is based on phospholipid oxidation.

Antinematodal activity of some tropical rainforest plants against the pinewood nematode, Bursaphelenchus xylophilus.

Abstract Sixty five methanolic extracts of Sumatran rainforest plants representing 63 species of 21 families were assayed in vivo for antinematodal activity against Bursaphelenchus xylophilus using our cotton ball-fungal mat method. Extracts of 27 plants species from 14 families exhibited antinematodal activity, while 37 species were inactive. Among them, three extracts of Bischofia javanica, Knema hookeriana and Areca catechu exhibited very strong activity at minimum effective dose (MED ) of 0.7 mg/cotton ball (mg/bl.). Eight extracts from Allamanda cathartica, Ervatamia corymbosa, Hoya diversifolia, Bischofia javanica, Derris malacensis, Melastoma melabathricum, Ophiorriza konsteleary and Brucea sumatrana also showed strong activity (MED, 5 mg/bl.).

Synthesis of Phospholipids Bearing a Conjugated Oxo-polyunsaturated Fatty Acid Residue

2-(15′-Oxo-5′,8′,11′,13′-eicosatetraenoyl)-1-stearoyl-sn-glycerol(3)phosphocholine (APC-CO) 1 and 2 and 2-(13′-oxo-9′,11′-octadecadienoyl)-1-stearoyl-sn-glycero(3)phosphocholine (LPC-CO) 3 are synthesized and an analytical system established for the determination of geometrical isomers at the 13′ position of APC-CO.

Two antinematodal phenolics from Knema hookeriana, a Sumatran rainforest plant.

Abstract The activity-guided chromatographic purification of the methanol extract of Knema hookeriana, using pine wood nematodes Bursaphelenchus xylophilus has successfully led to the isolation and characterization of two phenolic antinematodal compounds with minimun effective dose (MED) of 4.5 and 20 μg/cotton ball (μg/ bl.) or 0.018 and 0.073 μᴍ/cotton ball (μᴍ/bl.), respectively. Based on their chemical and spectral properties, these compounds were determined to be 3-undecylphenol (1) and 3-(8Z-tridecenyl)-phenol (2). These compounds were isolated for the first time from this species, and 2 seems to be a novel compound.

Eicosanyl p-Coumarates from a Kenyan Plant, Psiadia punctulata : Plant Growth Inhibitors

From methanol extracts of fresh leaves of Psiadia punctulata (DC.) Vatke, lettuce seed radicle growth inhibitors were isolated and identified as E- and Z-eicosanyl p-coumarates by spectroscopic analyses.

Glucosylation of Sucrose Laurate with Cyclodextrin Glucanotransferase

Sucrose monolauroyl esters were found to serve as substrates for cyclodextrin glucanotransferase (CGTase)-catalyzed transglucosidation reactions, affording new sucrose esters that have an additional 1-3 glucose residues on the pyranose ring of the sucrose moiety in the ester.

Termiticidal Activity of Diterpenes from the Roots of Euphorbia kansui

Five ingenane compounds, 1−5, kansuinins A and B, isolated from Euphorbia kansui, and their derivatives 7 and 9 were tested for termiticidal activity against the Japanese termite, Reticulitermes speratus. At 72 hours after treatment, the ingenane compounds 1 to 5 caused 100% mortality in R. speratus at 50, 25 and 12.5 μg/disk, respectively, except for compound 1, which gave a mortality rate of (93.06 ± 5.56)% at 12.5 μg/disk. At 36, 48 and 60 hours after treatment, compounds 1 to 5 showed more termiticidal activity than kansuinins A and B and their derivatives. The kansuinins showed no or only slight activity against termites in the filter paper bioassay under the conditions tested compared with a solvent control.

Antinematodal activities of ingenane diterpenes from Euphorbia kansui and their derivatives against the pine wood nematode (Bursaphelenchus xylophilus)

Under the bioassay-guided method, two diterpenes, 3-O-(2″,3″-dimethylbutanoyl)-13-Ododecanoylingenol (1) and 3-O-(2″,3″-dimethylbutanoyl)-13-O-decanoylingenol (2) isolated from Euphorbia kansui, showed a pronounced antinematodal activity against the nematode Bursaphelenchus xylophilus at the same minimum effective dose (MED) of 5 μg per cotton ball and still displayed antinematodal activity at a dose of 2.5 μg per cotton ball. Compounds 3 − 6 were obtained, and the structure of the new compound 6 was elucidated based on 1D-and 2D-NMR analyses and physicochemical data. Preliminary structure-biological activity relationships of ingenane-type compounds were deduced.

Cyclomaltodextrin Glucanotransferase-Catalyzed Transglycosylation from Dextrin to Alkanol Maltosides

Maltosides of butanol, octanol, and lauryl alcohol were found for the first time to serve as substrates for cyclomaltodextrin glucanotransferase (CGTase), and glycosyl residue was transfered from dextrin to the substrate affording novel maltosides with 3–4 glucose units.