Gunnar Bergström

Headspace volatiles of whole plants and macerated plant parts of Brassica and Sinapis

Headspace volatiles collected from six Crucifer species of the two genera Brassica and Sinapis were investigated by GC/MS. A total of 34 compounds were identified from both whole plants and macerated plant parts. Typical cell-degradation compounds including alcohols, aldehydes and glucosinolate breakdown products were primarily found in macerate samples, while terpenes were detected almost exclusively in whole plants. Macerated buds generally contained higher amounts of nitriles and isothiocyanates than did macerated leaves. Several compounds here identified have, to our knowledge, not been previously reported in Brassica and Sinapis.

Floral fragrance disparity between three taxa of lady's slipper cypripedium calceolus (orchidaceae)

Abstract The flower fragrances of three geographically separated intraspecific orchid taxa of Cypripedium calceolus, viz. the Eurasian subspecies calceolus and the North American varieties parviflorum and pubescens, were isolated by sorption on synthetic polymers and analysed by GC-MS. The three taxa were found to have distinctly different fragrances composed mainly of fatty acid derivatives, isoprenoids, and phenyl derivatives, respectively. Sexual reproduction is dependent on the deception of pollinating solitary bees, and the three taxon-specific chemical compositions most probably reflect functional evolution in relation to different bee faunas. This study suggests that floral fragrance analysis provides a useful taxonomic tool in Cypripedium.

Chemical basis of a highly specific mutualism: Chiral esters attract pollinating beetles in Eupomatiaceae

Abstract Eupomatia species are pollinated exclusively by weevils of the genus Elleschodes (Col., Curculionidae), which may have their entire lifecycle linked to the host plant. Flowers produce potent fragrances, which serve as attractants for the weevils. Chemical analyses showed that the volatiles almost entirely consist of short chain, fatty acid esters; in E. laurina, methyl (2S)-2-methylbutanoate made up over 97% of the fragrance, whereas methyl (2R)-2-acetoxy-4-methylpentanoate dominates the blend in E. bennettii. In E. bennettii, qualitative and quantitative differences, including enantiomeric composition, were found between the sexual phases. The chemical nature of other weevil attractants, and functional properties of the floral esters are discussed.

Floral fragrances in Cimicifuga: Chemical polymorphism and incipient speciation in Cimicifuga simplex

Abstract Floral fragrances in four species of Cimicifuga (Ranunculaceae) were collected by sorption and analyzed by gas chromatography-mass spectrometry. One pollination morph in C. simplex was found to contain three benzenoid compounds absent in the two other morphs. Two of these substances — methyl anthranilate and isoeugenol — induce behavioural modification in pollinating butterflies. The function of a range of terpenes present in small amounts in all analyzed species is unknown, but they may be involved in herbivore deterrence.

Floral fragrances in Actaea, using differential chromatograms to discern between floral and vegetative volatiles

Abstract Floral fragrances in four species of Actaea (Ranunculaceae) and a hybrid were studied by GC-MS. They consist primarily of 10–15 closely related monoterpenes, and differ quantitatively between species. In order to separate the volatiles actually produced by the flower, parallel collections were made from inflorescence and vegetative parts, respectively, and the volatiles of the latter were subtracted from the inflorescence sample. This method proved particularly effective when tested with a single plant individual and a long collection period.

Volatile Secretions in Three Species of Dufourea (Hymenoptera: Halictidae) Bees: Chemical Composition and Phylogeny

Abstract Volatile secretions from Dufour’s glands in three species of Dufourea bees, Dufourea (Halictoides) dentriventris (Nylander). D.(H.) inermis (Nylander) and D. (Dufourea) minuta Lepelletier have been studied by gas chromatography and mass spectrometry. It was found that the secretions are composed of complex blends of straight chain saturated and unsaturated 2- and 3-ketones and scries of hexanoic and octanoic esters. Cephalic secretions from males and females of D.(H.) inermis and D.(D.) minuta contain sex- and species-specific blends of methylcarbinols and corresponding long chain carboxylic esters. Mass spectrometric fragmentation patterns of esters are described.

Multicomponent Mandibular Gland Secretions in Three Species of Andrena Bees (Hym., Apoidea)

Abstract 50 volatile constituents of the mandibular gland secretions in males and females of three species of Andrena bees, A. wilkella (Chr.), A. ovatula (K .) and A. ocreata (K .), have been identified. The secretions are made up of a series of spiroacetals of four different systems together with mono-terpenes and unbranched acyclic compounds. Many of the components, particularly several of the dominant ones, occur in both sexes of all three species, so that the volatile secretions are qualitatively very similar. Females contain about 100 μg per individuum , which is 3-5 times the amount of the males’ secretions. Major spiroacetals are E,E- and Z ,E-2,8-dimethyl-1,7-dioxa-spiro[5.5]undecane and E,E-and Z,E-2-ethyl-7-methyl-1,6-dioxaspiro[4.5]undecane, while prominent monoterpenes are geraniol and citronellol. Straight chain hydrocarbons C17, C19, C21 and C23 occur in fairly large amounts, mostly with increasing concentrations. With respect to the quantitative distribution of components of minor concentration, the bouquet of A. wilkella is clearly distinguishable from A. ovatula and A. ocreata which from the morphological and ethological point of view are more closely related. Behaviour tests with A. wilkella indicate high biological activity of the main spiroacetal.

The sex pheromones of two pine sawfly species, Gilpinia frutetorum and Gilpinia socia : Chemical identification, synthesis and biological activity

3,7-Dimethylpentadecan-2-ol and 3-methylpentadecan-2-ol were identified in female whole body extracts from the two pine sawfly species Gilpinia frutetorum and Gilpinia socia. This is the first observation of 3-methylpentadecan-2-ol in extracts of a female pine sawfly species. Synthetic and highly pure stereoisomers of 3,7-dimethylpentadecan-2-ol and 3-methylpentadecan-2-ol were used to verify that the (2S,3R,7R)-isomer of 3,7-dimethylpentadecan- 2-ol and (2S,3R)-3-methylpentadecan-2-ol were present in the extracts. The four stereoisomers of 3-methylpentadecan-2-ol and their biologically active esters were produced via chemoenzymatic methods and the synthesis is described in detail. Male G. socia antennae responded strongly in EAG recordings to the (2S,3R)-isomer of the acetate and propionate of 3-methylpentadecan-2-ol. Male antennae of both G. frutetorum and G. socia also responded to the (2S,3R,7R)- and (2S,3R,7S)-acetates of 3,7-dimethylpentadecan-2-ol

Volatile Compounds from Cephalic Secretions of Females in two Cleptoparasite Bee Genera, Epeolus (Hym., Anthophoridae) and Coelioxys (Hym., Megachilidae)

Abstract Volatile cephalic secretions from females of four cleptoparasitic bee species, Epeolus cruciger (Pz.), E. variegatus, (L.) (Anthophoridae) and Coelioxys (Coelioxys) quadridentata (L.), C. (Schizocoelioxys) mandibularis Nyl. (Megachilidae) were analysed by combined gas chromatography/mass spectroscopy. There are considerable similarities between the two species within each genus, and also some qualitative correspondences between the two genera. The Epeolus species contain spiroacetals, 2-alkanols and pyrazines while the Coelioxys species contain spiroacetals, 3-alkanols and 3-ketones along with unsaturated alcohols. Two of the spiroacetals are first found in nature.

Species and Sex Specificity in the Odour Composition of Two Panurgine Bees (Hymenoptera, Andrenidae)

Abstract From the volatile constituents of the solitary bee species Panurgus banksianus Kirby and P. calcaratus Scopuli 31 compounds could be identified. The cephalic secretion of P. banksianus is a sex specific m ulticomponent mixture of terpenes and aliphatic carboxylic acid esters while P. calcaratus contains monoterpenes only. The major component in the Dufour’s gland secretion of P. banksianus is a macrocyclic lactone, eicosanolide, which is absent in P. calcaratus. In contrast, the new terpenoid ester, geranyl citronellate, is present in large amounts in the Dufour’s gland secretion of P. calcaratus.