Raphael Ikan

The pheromone of the queen of the Oriental hornet, Vespa orientalis

Abstract From an extract of heads of the queens of the Oriental hornet, Vespa orientalis, a pheromone has been isolated and identified as δ-n-hexadecalactone:

Investigations on the structural units of melanoidins

A series of sugar-amino acid derived melanoidins were synthesized and their chemical and physical properties were evaluated using spectral, chemical and thermal analyses. It is suggested that the melanoidin “back-bone” is probably a sugar-moiety polymer in which various nitrogen containing groups are grafted. Some resemblance between marine humics and synthetic melanoidins was found.

The presence of pheromones in the Oriental hornet, Vespa orientalis F.

Abstract The social organization of the Oriental hornet, Vespa orientalis F., has been studied, particularly the nest behaviour of the queen and the workers. A first report on the fractionation of the extracts of heads and bodies of queen wasps is presented. The strongly acidic fraction obtained contains the ‘Queen Substance’.

The carotenoid pigments in the juice and flavedo of a mandarin hybrid (Citrus reticulata) cv michal during ripening

Abstract The carotenoid pigments ofthe mandarin hybrid ( Citrus reticulata ) cv Michal, in the juice and flavedo were characterized at three ripening stages, before, during and after colour break. During ripening the characteristic mandarin pattern was formed in the juice, which contained cryptoxanthin as the principal pigment. In the flavedo the chloroplast carotenoid pattern of the green fruit changed into the characteristic pattern of C. reticulata with a high level of citraurin which, together with cryptoxanthin, imparts an intensive reddish tint to the hybrid. The flavedo contained an unusual C 30 apocarotenoid, β-citraurinene (8′-apo-β-caroten-3-ol). The flavedo carotenoids of this accidental hybrid were compared with the carotenoids of the presumed parents Dancy tangerine and Clementine. The hybrid resembles more the second parent, from which it inherited the ability to biosynthesize a higher amount of citraurin as well as citraurinene. Citraurinene, considered a Citrus hybrid-specific pigment, was found for the first time in a Citrus variety. A possible biosynthetic pathway of the Citrus C 30 -apocarotenoids is proposed.

Food exchange between adults and larvae in Vespa orientalis F

Abstract Colonies of Vespa orientalis cannot exist without the larvae or, more specifically, without larval salivary secretion, which is the only source of raw materials for nitrogen metabolism and egg production available to the workers and the queen, who do not themselves possess the proteases necessary for protein degradation. This finding suggests that social life among wasps is probably a symbiosis between the adults and larvae.

Carbon-13 cross polarized magic-angle samples spinning nuclear magnetic resonance of melanoidins

Abstract Melanoidins synthesized from amino-acids and sugars in various ratios and humic substances from Hula Basin (Israel) have been investigated by 13 C-CP/MAS NMR spectroscopy. Most spectra indicated a significant similarity between melanoidins and humics. It is suggested that the Maillard reaction plays a more significant role in the formation of humic substances than the “traditional” theory based on a lignin source. Several heterocyclic and heteroaromatic moieties (mainly furanoid, hydroxy-alkyl-furanone and hydroxy-alkyl-cyclopentenone) have been considered as major “building blocks” of humic substances and melanoidins. Aromaticities calculated from NMR spectral data of SM (“sugar” enriched melanoidins) and AAM (amino acid enriched melanoidins) coincide remarkably with the aromaticities of terrestrial and marine humics, respectively.

Endo-β-glucosidase from Aspergillus niger grown on a monoterpene glycoside-containing medium

Abstract An endo-β-glucosidase was isolated from Aspergillus niger grown on a medium containing rutin as the sole carbon source, and was partially purified by affinity chromatography. The enzyme was found to be extracellular. Its optimum pH was 3.4, and its optimum temperature 65°. K M values were 1 mM (PNPG) and 1.25 mM (geranyl-β-rutinoside), V max values were 0.22 μmol/min/mg protein (PNPG) and 0.08 μmol/min/mg protein (geranyl-β-rutinoside), and K I was 40 mM (glucose). The enzymes activity was not inhibited by fructose, sucrose or SO 2 , and was enhanced by ethanol. No loss of activity was found after seven days at 50°. M r determined by gel filtration was 120 000. Using polyacrylamide isoelectric focusing gel, a pI of 3.9 was obtained.

Thermal evaluation of some model melanoidins by Curie point pyrolysis-mass spectrometry and gas chromatography-mass spectrometry

Abstract Melanoidins of glucose or galactose and the amino acids tyrosine, methionine and lysine were analysed by Curie point pyrolysis-mass spectrometry and pyrolysis-gas chromatography-mass spectrometry. Specific chain characteristics of the reactant amino acids were visible in the pyrolysis data, whereas pyrolysis products of carbohydrates related structural elements in the melanoidins were found to be more sensitive to the nature of the amino acids and the sugar amino acid ratio. The influence of the pyrolysis temperature was tested on galactose-lysine melanoidins by comparison of pyrolysis-mass spectra obtained at 510, 610 and 770°C using multivariate data analysis techniques. The effect of the end temperature on the spectra of this melanoidin was found to be small.

Characterization of melanoidins by IR spectroscopy—I. Galactose-glycine melanoidins

Abstract A comparative IR spectral study was conducted with synthetic melanoidins which were prepared from various ratios of sugars and amino acids and a pseudomelanoidin which was prepared from sugar only. A significant resemblance was observed between the pseudomelanoidin and the melanoidin prepared from a high (9:1) sugar ratio (type 1). Another series of melanoidins (type 2) consists of those prepared from an “excess” of amino acid (9:1 and 1:1). Type 1 showed the presence of carbonyl and hydroxyl groups as well as aromatic vibrations. The same groups were detected in the spectrum of the pseudomelanoidin. These features were observed in a very low concentration in the type 2 melanoidins. Carboxylic groups are present in pseudomelanoidin and in both types of the melanoidins. However, the acid strength of this group is high in melanoidin of type 2, but low in type 1 and in the pseudomelanoidin. The nitrogen atom which is involved in the melanoidin structure is present as a tertiary amine. Heat treatment of KBr discs containing glycine, galactose and a mixture thereof revealed that galactose was converted into pseudomelanoidin; a mixture of galactose-glycine yielded the corresponding melanoidin of type 2; no reaction was observed with glycine.

Lipids of the thermophilic alga Cyanidium caldarium

Abstract A series of fatty acids (C 8 –C 20 ), both, saturated and unsaturated and sterols (C 27 –C 29 ) were identified in the alga, Cyanidium caldarium , using chromatographic and spectroscopic methods. Some phylogenetic consequences of the results are discussed.