scholarly journals Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part II: Iridomyrmecins

2012 ◽  
Vol 8 ◽  
pp. 1256-1264 ◽  
Author(s):  
Robert Hilgraf ◽  
Nicole Zimmermann ◽  
Lutz Lehmann ◽  
Armin Tröger ◽  
Wittko Francke
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Stereoselective Synthesis ◽  
Minor Component ◽  
Parasitoid Wasp ◽  
Enantioselective Gas Chromatography ◽  
A Minor

Following our earlier approach to the synthesis of dihydronepetalactones, all eight stereoisomers of trans-fused iridomyrmecins were synthesized starting from the enantiomers of limonene. Combined gas chromatography and mass spectrometry including enantioselective gas chromatography revealed that volatiles released by the endohyperparasitoid wasp Alloxysta victrix contain (4S,4aR,7S,7aR)-iridomyrmecin of 95–97% ee and stereochemically pure (4S,4aS,7R,7aS)-iridomyrmecin as a minor component.

scholarly journals Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part I: Dihydronepetalactones

2012 ◽  
Vol 8 ◽  
pp. 1246-1255 ◽  
Author(s):  
Nicole Zimmermann ◽  
Robert Hilgraf ◽  
Lutz Lehmann ◽  
Daniel Ibarra ◽  
Wittko Francke
Keyword(s):  
Mass Spectrometry ◽  
Stereoselective Synthesis ◽  
Minor Component ◽  
Parasitoid Wasp ◽  
The Other ◽  
Enantiomerically Pure ◽  
Enantioselective Gas Chromatography ◽  
A Minor ◽  
Stereogenic Center ◽  
Reference Samples

Starting from the enantiomers of limonene, all eight stereoisomers of trans-fused dihydronepetalactones were synthesized. Key compounds were pure stereoisomers of 1-acetoxymethyl-2-methyl-5-(2-hydroxy-1-methylethyl)-1-cyclopentene. The stereogenic center of limonene was retained at position 4a of the target compounds and used to stereoselectively control the introduction of the other chiral centers during the synthesis. Basically, this approach could also be used for the synthesis of enantiomerically pure trans-fused iridomyrmecins. Using synthetic reference samples, the combination of enantioselective gas chromatography and mass spectrometry revealed that volatiles released by the endohyperparasitoid wasp Alloxysta victrix contain the enantiomerically pure trans-fused (4R,4aR,7R,7aS)-dihydronepetalactone as a minor component, showing an unusual (R)-configured stereogenic center at position 7.

Composition of the sterol fraction of caprine milk fat by gas chromatography and mass spectrometry

2000 ◽  
Vol 67 (3) ◽  
pp. 437-441 ◽  
Author(s):  
MARÍA J. FRAGA ◽  
JAVIER FONTECHA ◽  
LUCIDIA LOZADA ◽  
ISABEL MARTÍNEZ-CASTRO ◽  
MANUELA JUÁREZ
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Milk Fat ◽  
Cholesterol Content ◽  
Sterol Fraction ◽  
Unsaponifiable Fraction ◽  
Caprine Milk ◽  
A Minor ◽  
Cholesterol Precursors ◽  
Layer Chromatography

The sterol fraction of milk is of nutritional interest because high levels of cholesterol in plasma (modulated by the cholesterol ingested) are associated with an increasing risk of cardiovascular disease. In addition, some sterols (ergosterol and 7-dehydrocholesterol) are provitamins (D2 and D3 respectively). At the same time, through the study of the sterol fraction, vegetable fats can be detected in milk and dairy products. Sterols are a minor fraction of total milk fat, the main sterol being cholesterol (3 mg/g fat, equivalent to 100 mg/l cows' milk). Small quantities of other sterols (7-dehydrocholesterol, 22-dehydrocholesterol, ergosterol, fucosterol, lanosterol, lathosterol, 24-methylenecholesterol) and several phytosterols have been reported in cows' milk (Walstra & Jennes, 1984). International Dairy Federation (1992) states that in the sterol profile of genuine milk fat there may appear, in addition to the peak of 7-dehydrocholesterol which ranges from 0·7 to 4% of total sterols, < 1% of minor sterols with retention times corresponding to phytosterols.Values for the cholesterol content of goats' milk vary considerably, from 211 mg/l (Pantulu et al. 1975) to 125 mg/l (Lu, 1993), partly owing to the use of different analysis techniques. Some of these values were obtained using non-specific colorimetric methods, which are inaccurate in the presence of cholesterol precursors or phytosterols (Clark et al. 1983; Haugh & Harzer, 1984). Some minor peaks have been assumed to be sterols but have not been identified (García-Olmedo & Barrera, 1985).Conventional methods of sample preparation for sterol analysis prior to gas chromatography (GC), which involve saponification of fat with or without isolation of the sterol fraction by thin layer chromatography, are tedious and time-consuming. Transesterification with KOH–methanol has been successfully used as a rapid alternative for obtaining the unsaponifiable fraction.This paper describes the identification of sterols (cholesterol and other minor sterols) in goats' milk fat using an alkali-catalysed transesterification procedure prior to GC and GC–mass spectrometry (GC–MS) analysis.

scholarly journals Mate attraction, chemical defense, and competition avoidance in the parasitoid wasp Leptopilina pacifica

Chemoecology ◽  
2020 ◽  
Author(s):  
Lea C. Böttinger ◽  
Frederic Hüftlein ◽  
Johannes Stökl
Keyword(s):  
Sex Pheromone ◽  
Defensive Secretion ◽  
Minor Component ◽  
Parasitoid Wasp ◽  
Primary Component ◽  
Sister Species ◽  
Wasp Species ◽  
Competition Avoidance ◽  
Species Specific ◽  
A Minor

AbstractA major hypothesis for the evolution of chemical signals is that pheromones arise from non-communicative precursor compounds. However, data supporting this hypothesis are rare, primarily because the original functions of the antecedent compounds often have been lost. A notable exception, however, is the parasitoid wasp species Leptopilina heterotoma, whose compound (−)-iridomyrmecin is used as a defensive secretion, a cue for females to avoid competition with con- and hetero-specific females, and as the primary component of the females’ sex pheromone. To better understand the evolution of sex pheromones from defensive compounds, we examined the chemical ecology of L. pacifica, the sister species of L. heterotoma. Here, we show that L. pacifica also produces a defensive secretion containing a species-specific mixture of mostly iridoid compounds. However, the composition of the secretion is more complex than in L. heterotoma, and iridomyrmecin is only a minor component. Moreover, in contrast to L. heterotoma, conspecific female competitors were not avoided by female subjects, and a role of the iridoids in the female sex pheromone of L. pacifica can be excluded, as only the females’ cuticular hydrocarbons (CHCs) resulted in the elicitation of courtship by males. Although closely related, the two sister species show substantial differences in the use of the defensive secretion for communicative purposes. Variation in pheromone usage in this genus still presents a conundrum, highlighting the need for additional studies to understand the selective forces shaping the evolution of pheromone composition.

The isolation and identification of makisterone A from the yew, Taxus cuspidata

1977 ◽  
Vol 55 (7) ◽  
pp. 1129-1134 ◽  
Author(s):  
Brenton Garth Burns ◽  
Michael Wilson Gilgan
Keyword(s):  
Mass Spectrometry ◽  
Nuclear Magnetic Resonance ◽  
Trimethylsilyl Ether ◽  
Minor Component ◽  
Reversed Phase ◽  
Taxus Cuspidata ◽  
Isolation And Identification ◽  
Nuclear Magnetic Resonance Spectrometry ◽  
Magnetic Resonance Spectrometry ◽  
A Minor

The ecdysteroids were extracted from yew, Taxus cuspidata, needles and twigs and recovered from the aqueous extract by reversed phase adsorption. Purification of the ecdysteroids was achieved by a single solvent partition and a dry column chromatogram followed by fractionation on an adsorptive Porasil A (60) column. Makisterone A was a minor component identified by melting point, liquid chromatography, gas chromatography of the trimethylsilyl ether, mass spectrometry, and nuclear magnetic resonance spectrometry. A second minor component was isolated but not identified.

Sign in / Sign up

Export Citation Format

Share Document