The volatile components of the Dufour's gland secretion of female halictid bees have been examined in 18 Nearctic species belonging toAgapostemon, Augochlora, Augochlorella, Augochloropsis, Dialictus, Evylaeus, Halictus, andLasioglossum. Nine saturated and unsaturated macrocyclic lactones ranging from C18 to C26 have been identified. Four of these compounds, the saturated C26 and the unsaturated C20, C22, and C24 lactones, are new natural products reported for halictine bees. A series of eight esters containing branched C5-alkenols and fatty acids has been identified in several species. The cell linings and pollen ball inAugochlora pura pura contain the same major lactones as the Dufour's gland. A discussion of the significance of the Dufour's gland secretion for apoid systematics and its function in the Halictidae is presented.
The volatile components of the Dufour's gland secretions were examined in 22 Nearctic species of andrenid bees representing 10 subgenera. Farnesyl hexanoate was the dominant component in the secretion of 17 species. In others, various terpenoid esters such as geranyl octanoate, farnesyl octanoate and geranylgeranyl octanoate were the major components. Approximately 30 compounds have been identified in the secretions; many are newly identified in andrenid bees. Three different groups of secretions are discerned with "exceptions." A discussion of the possible function of the Dufour's gland secretion in the biology of, and its use in, the systematics of these bees is presented.
Quantitative estimation of isotopic enrichment and concentrations of keto analogs of branched-chain amino acids in biological fluid has been used for the study of protein metabolism in animal and human studies. At present, O-trimethylsilyl-quinoxalinol derivative is used widely in the quantification of branched-chain alpha-keto acids. In the present study, N-methyl-quinoxalone derivative was developed and its use in quantification in human studies verified. O-phenylenediamine and alpha-keto acid react in acidic media to yield phenolic and amide tautomers. O-trimethylsilyl-quinoxalinol derivative of the phenolic tautomer is used at present for quantification by chemical ionization/selected ion monitoring. We have prepared N-methyl-quinoxalone derivative using N,N-dimethyl formamide dimethyl acetal. This derivative is characterized by a major amide form and a minor phenolic form. The mass spectrum has a characteristic fragment, which facilitates easy identification and quantitation by electron impact/selected ion monitoring. Because m/z 174 was observed as the base peak for alpha-ketoisocaproate, alpha-keto-beta-methylvalerate and alpha-ketoisovalerate, "single ion monitoring' could be performed for the quantification of isotopic enrichment as well as plasma concentration of these three branched-chain alpha-keto acids. Isotopic enrichment from 0.25 to 7.5 at% excess could be measured easily, with an average coefficient of variation of less than 8%. Plasma concentrations as low as 10 microM l-1 in a 200-microliters aliquot could be measured. Methyl migration was an interesting feature of the mass spectrometric fragmentation pattern of the alpha-keto acids. The mechanism of methyl migration is proposed and discussed. This paper also describes some of the studies involved in the formation of isomeric O- and N-alkyl, -quinoxaline and -quinoxalone using a number of N,N-dimethyl formamide dialkyl acetals.
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