Barend V. Burger

Isolation of the major germination cue from plant-derived smoke

A highly active, heat stable, long lasting compound, 3- methyl-2H-furo[2,3-c]pyran-2-one (1), that stimulates seed germination was isolated from plant-derived smoke water using bioactivity-guided fractionation. The identification of this natural molecule, the major germination cue from smoke, should now rapidly lead to a more comprehensive understanding of the role of smoke as a promoter of seed germination.

Characterization of Volatiles and Aroma-Active Compounds in Honeybush (Cyclopia subternata) by GC-MS and GC-O Analysis

Volatile organic compounds (VOCs) in fermented honeybush, Cyclopia subternata, were sampled by means of a high-capacity headspace sample enrichment probe (SEP) and analyzed by gas chromatography-mass spectrometry (GC-MS). Stereochemistry was determined by means of enantioselective GC-MS with derivatized β-cyclodextrin columns as chiral selectors. A total of 183 compounds, the majority of which are terpenoids (103; 56%), were identified by comparing their mass spectra and retention indices with those of reference compounds or tentatively identified by comparison with spectral library or literature data. Of these compounds, 37 were determined by gas chromatography-olfactometry (GC-O), using detection frequency (DF) and aroma extract dilution analysis (AEDA), to be odor-active (FD ≥ 2). (E)-β-Damascenone, (R/S)-linalool, (E)-β-damascone, geraniol, (E)-β-ionone, and (7E)-megastigma-5,7,9-trien-4-one were identified with the highest FD factors (≥512). The odors of certain compounds, that is, (6E,8Z)-megastigma-4,6,8-trien-3-one, (6E,8E)-megastigma-4,6,8-trien-3-one, (7E)-megastigma-5,7,9-trien-4-one, 10-epi-γ-eudesmol, epi-α-muurolol, and epi-α-cadinol, were perceived by GC-O assessors as typically honeybush-like.

Olfactory Cue Mediated Neonatal Recognition in Sheep, Ovis aries

The strong bond between ewe and lamb formed shortly after parturition is an important factor in lamb survival. Evidence exists that a ewe can distinguish her lamb by its unique smell, but the constituents of such a putative olfactory cue have not yet been identified. We have now identified 133 volatile organic compounds associated with the wool of Döhne Merino lambs that we presume may be involved in neonatal recognition. Quantitative analysis and comparison of odor profiles of the twins of 16 ewes (9.69% sample group) of a flock of 165 twin-bearing ewes revealed that the wool volatiles of twins are qualitatively and quantitatively similar, but differ from those of other twins or non-twin lambs in the flock. The 88 constituents present in at least 20% of the analyzed wool samples were considered as variables for multivariate analysis. A P-value < 0.001 was calculated, indicating that the pairing of twins according to the qualitative and quantitative composition of the wool was significant. Bioassays carried out during the lambing seasons of 2009 and 2010 confirmed the previously established role of lamb odor in ewe-lamb recognition. However, when alien lambs were dressed in jackets sprayed with synthetic mixtures formulated to match the chemical composition of the effluvia of the ewes’ own lambs, ewes rejected the aliens. This is possibly because the VOCs were not released in quantitative ratios sufficiently accurate to emulate the odor of the ewes’ own lambs.

Triterpenoid saponins from Becium Grandiflorum var. obovatum

Two new triterpenoid saponins, beciumecine 1 and 2, were isolated from the root bark of Becium grandiflorum var. obovatum and their structures established as 3-O-(beta-D-glucopyranosyl) terminolic acid 28-O-beta-D-apiofuranosyl(1-3)-[alpha-L-rhamnopyranosyl (1-3)-beta-D-xylopyranosyl(1-4)]-alpha-L-rhamnopyranosyl (1-2)-alpha-L-arabinopyranoside and 3-O-(beta-D-glucopyranosyl) 24-hydroxyterminolic acid 28-O-alpha-L-rhamnopyranosyl(1-3)-beta-D-xylopyranosyl(1-4)-alpha-L- rhamnopyranosyl(1-2)-alpha-L-arabinopyranoside, respectively.

Conformational Analyses of Alkylated β-Cyclodextrins by NMR Spectroscopy

β-Cyclodextrin was derivatized with 1-bromoalkanes of different chain lengths. The yield as well as the purity of the resulting cyclodextrin derivatives were improved by using solvent mixtures instead of pure solvents. The heptakis(2,6-di-O-alkyl)- and heptakis(2,3,6-tri-O-alkyl)-β-cyclodextrins were studied by means of NMR spectroscopy employing one-dimensional as well as two-dimensional NMR techniques. Analysis of the NMR data showed that only in completely derivatized β-cyclodextrins the cyclodextrin torus undergoes a conformational change. Best separation factors were found for the cyclodextrin derivative with the highest internal mobility as determined from the corresponding NT1-values, the validity of which was confirmed by NOE determinations. Therefore, 13C relaxation times could be used as a measure of the efficiency and usefulness of a given cyclodextrin derivative as an enantioselective stationary phase.

Comparison of headspace-oxylipin-volatilomes of some Eastern Himalayan mosses extracted by sample enrichment probe and analysed by gas chromatography-mass spectrometry.

Mosses have an inherent adaptability against different biotic and abiotic stresses. Oxylipins, the volatile metabolites derived from polyunsaturated fatty acids (PUFAs), play a key role in the chemical defence strategy of mosses. In the present study, a comparative survey of these compounds, including an investigation into their precursor fatty acids (FAs), was carried out for the first time on the mosses Brachymenium capitulatum (Mitt.) Paris, Hydrogonium consanguineum (Thwaites & Mitt.) Hilp., Barbula hastata Mitt., and Octoblepharum albidum Hedw. collected from the Eastern Himalayan Biodiversity hotspot. Their headspace volatiles were sampled using a high-efficiency sample enrichment probe (SEP) and were characterized by gas chromatography-mass spectrometric analysis. FAs from neutral lipid (NL) and phospholipid (PL) fractions were also evaluated. Analysis of the oxylipin volatilome revealed the generation of diverse metabolites from C5 to C18, dominated by alkanes, alkenes, saturated and unsaturated alcohols, aldehydes, ketones and cyclic compounds, with pronounced structural variations. The C6 and C8 compounds dominated the total volatilome of all the samples. Analyses of FAs from membrane PL and storage NL highlighted the involvement of C18 and C20 PUFAs in oxylipin generation. The volatilome of each moss is characterized by a ‘signature oxylipin mixture’. Quantitative differences in the C6 and C8 metabolites indicate their phylogenetic significance.

Identification, Synthesis, and Field Tests of the Sex Pheromone of Margarodes prieskaensis (Jakubski)

Here, we report the identification and synthesis of the sex pheromone of female Margarodes prieskaensis (Jakubski), and the attractiveness of the synthetic pheromone to males in field trapping tests. Volatile organic compounds were collected from virgin females using a sample enrichment probe (SEP). Analyses by gas chromatography coupled to mass spectrometry revealed the presence of only two constituents. By scaling up the SEP, sufficient of the major constituent was collected for 1H and 13C nuclear magnetic resonance (NMR) analyses and ancillary NMR techniques. The sex attractant was identified as (2R,4R,6R,8R)-2,4,6,8-tetramethylundecan-1-ol. The enantiomerically pure compound was synthesized from octadecyl (2R,4R,6R,8R)-2,4,6,8-tetramethylundecanoate, a minor component of the uropygial (preen) gland secretion of the domestic goose, Anser domesticus. Field trapping experiments, carried out in vineyards in the Northern Cape Province of South Africa, showed that the synthetic compound was as attractive to winged males of M. prieskaensis as virgin females. The second compound detected was identified as the corresponding acetate, but addition of this did not affect the attractiveness of the major component. We believe this to be the first identification of a sex attractant of the Margarodidae.

Characterization of amniotic fluid of Dohne Merino ewes (Ovis aries) and its possible role in neonatal recognition.

Abstract Amniotic fluid (AF) was investigated as a possible source of the neonatal recognition cue that plays a crucial role in ewe–lamb bonding in sheep. A total of 70 of the 133 volatile organic compounds (VOCs), previously identified in the cranial wool of neonatal Dohne Merino lambs, was also identified in AF collected individually from neonatal twins. As in the case of the wool of neonatal lambs, the VOC profiles (GC-MS) of the AF of twins were remarkably similar. However, the VOC profiles of the AF differed from that of the wool VOCs of the same lambs. The VOCs that best represent the total variance in the AF and wool of neonatal lambs were not identified as ligands of the AF proteins. These observations suggest that it is unlikely that the neonatal recognition cue of sheep could be a maternal label derived from the AF in which a lamb is born, and that the neonatal recognition cue is probably produced by the lamb. Taking cognizance of the temporal changes that take place in the quantitative composition of the cranial wool VOCs, we hypothesize that components of the neonatal recognition cue are already produced by the lamb well before its birth and that the quantitative composition in which these volatiles are released into the AF does not correspond to the composition of the recognition cue of the lamb at its birth. When grooming the newborn lamb, its mother removes AF containing incorrect chemical information from her lamb’s body and this affords her enough time to learn its personal recognition cue.

Neonatal Recognition in Sheep

The strong bond formed between ewe and lamb shortly after parturition is an important factor in lamb survival. Evidence exists that the ewe can distinguish her lamb by its unique smell, but the constituents of such a putative pheromone have not yet been identified. We have identified 133 volatile organic compounds in the cranial wool of Dohne Merino lambs that are presumably constituents of the neonatal recognition cue of this sheep race. Quantitative analysis and comparison of the odour profiles of the twins of 16 ewes of a flock of 165 twin-bearing ewes (9.69% sample group) revealed that the wool volatiles of twins are qualitatively as well as quantitatively practically identical, but differ from those of other twins or non-twin lambs in the flock. The 88 constituents present in at least 20% of the analysed wool samples were considered as variables for multivariate analysis. A P-value <0.0001 was calculated, indicating that the pairing of twins according to the qualitative and quantitative composition of the wool is statistically highly significant. Bioassays carried out during the lambing seasons of 2009 and 2010 confirmed the previously established role of the odour of lambs in ewe-lamb recognition. However, ewes rejected alien lambs dressed in jackets that were sprayed with mixtures formulated with synthetic analogues of the identified wool volatiles according to the qualitative and quantitative compositions of the experimental ewes’ own lambs. This is probably due to the volatiles not being released into the atmosphere in quantitative ratios emulating the odour of the lambs accurately enough to satisfy the experimental ewes.