应用液液萃取与分馏技术定性绵柔型蓝色经典微量挥发性成分

应用液液萃取和分馏技术研究了绵柔型洋河蓝色经典酒微量挥发性成分,经GC-MS检测,共检测到933个峰,已经鉴定的化合物672种,未鉴定但有色谱峰的化合物261种。白酒微量成分除原先检测到的醇类、醛类、酮类、酸类、酯类、芳香族、酚类、硫化物、呋喃类、氧杂环/环氧化合物、缩醛类、吡咯及吡啶类等化合物外,首次检测到萜烯与内酯类化合物。     

Systemic Induction of Allelochemicals in Glanded and Glandless Isogenic Cotton by Spodoptera exigua Feeding

Induction of systemic resistance to feeding of beet armyworm, Spodoptera exigua, was investigated in two isogenic lines of Stoneville 213 cotton, Gossypium hirsutum, that differed in the presence of pigment glands. In laboratory bioassays, larvae strongly preferred to feed on glandless cotton plants when presented a choice between undamaged terminal leaves of undamaged glanded and glandless plants. Feeding damage inflicted by S. exigua larvae on the two oldest leaves of glanded plants seven days prior to feeding bioassays caused larvae to prefer by 33-fold the undamaged terminal foliage from undamaged plants compared to that from damaged plants. Feeding damage on glandless plants caused only a 2.6-fold greater preference for terminal foliage from undamaged plants over foliage from previously damaged plants. Extracts of terminal foliage from glanded cotton damaged seven days earlier had significantly greater quantities of terpenoid aldehydes (hemigossypolone, gossypol, and heliocides) than did foliage from undamaged glanded plants. Terpenoid aldehydes were undetectable in extracts of both undamaged and previously damaged glandless plants. The profile of volatile compounds collected from the headspace of mechanically damaged terminal leaves of undamaged glanded and glandless plants differed. Both cotton isolines released large quantities of lipoxygenase products (hexenyl alcohols, acetates, and butyrates), but glandless plants released only small amounts of mono- and sesquiterpenes compared to glanded plants. Glandless plants damaged seven days prior to volatile collection released significantly greater quantities of lipoxygenase products, -ocimene, and - and -farnesene than did undamaged glandless plants. Previously damaged glanded plants released significantly greater quantities of all mono- and sesquiterpenes and hexenyl acetates and butyrates, but not alcohols. The relative importance of volatile compounds versus terpenoid aldehydes in induced feeding deterrence in cotton to S. exigua larvae is still unclear.     

A Simple Method to Extract Essential Oils from Tissue Samples by Using Microwave Radiation

A microwave protocol to extract lipophilic substances from tissue was modified to extract essential oils (EOs) from plant tissue and insect feculae. The material, in a solvent transparent to microwave radiation, is exposed for a short time to steam in a microwave oven. EO extracts are analyzed directly by GC or GC-MS when plant material is fresh and terpenes contained in glandular structures on leaf surfaces are readily released into the solvent. For dried material or insect feculae, mechanical means are utilized first to break up tissue; however, the complete procedure is carried out inside the same vial to reduce losses. Statistical analysis shows that the reproducibility of the modified method is high. Several samples can be run within an hour with this method.     

Head‐to‐Head Prenyl Synthases in Pathogenic Bacteria

Many organisms contain head‐to‐head isoprenoid synthases; we investigated three such types of enzymes from the pathogens Neisseria meningitidis, Neisseria gonorrhoeae, and Enterococcus hirae. The E. hirae enzyme was found to produce dehydrosqualene, and we solved an inhibitor‐bound structure that revealed a fold similar to that of CrtM from Staphylococcus aureus. In contrast, the homologous proteins from Neisseria spp. carried out only the first half of the reaction, yielding presqualene diphosphate (PSPP). Based on product analyses, bioinformatics, and mutagenesis, we concluded that the Neisseria proteins were HpnDs (PSPP synthases). The differences in chemical reactivity to CrtM were due, at least in part, to the presence of a PSPP‐stabilizing arginine in the HpnDs, decreasing the rate of dehydrosqualene biosynthesis. These results show that not only S. aureus but also other bacterial pathogens contain head‐to‐head prenyl synthases, although their biological functions remain to be elucidated.     

Role of Detoxification of Plant Secondary Compounds on Diet Breadth in a Mammalian Herbivore, Trichosurus vulpecula

Theory predicts that mammalian herbivores detoxify different classes of plant secondary compounds via separate metabolic pathways and that generalist herbivores maintain broad diet breadth to avoid overloading individual detoxification pathways. We tested the hypothesis that a generalist marsupial herbivore, the common brushtail possum, Trichosurus vulpecula, can maintain a higher intake of food when allowed to select from two diets containing different profiles of secondary compounds (phenolics and terpenes) than when given access to the diets individually. Diets consisted of a fruit and vegetable mash to which was added ground leaves of either Eucalyptus melliodora or E. radiata. E. melliodora and E. radiata differ in their concentrations and types of secondary compounds. Brushtail possums include these eucalypt species as part of their natural diet. We measured food consumption and detoxification metabolites of possums on these diets. Consistent with the hypothesis, animals presented with a choice of both diets consumed more food than animals given diets singly. One of the two indicators of detoxification, acid load in urine, differed significantly between diets while the other, glucuronic acid, did not. These results provide partial support for the hypothesis that diet breadth is governed by detoxification abilities.     

Relationships betweenDendroctonus micans Kug. (Coleoptera: Scolytidae) survival and development and biochemical changes in Norway Spruce,Picea abies (L.) Karst., phloem caused by mechanical wounding

The bark of Norway spruce trees,Picea abies (L.) Karst., was wounded to produce areas of bark with differing biochemical characteristics. Adults and larvae ofDendroctonus micans Kug. were inserted into these trees at points around the wounds. Larval survival was higher, larval dry weights were higher, and adults were more likely to oviposit at sites around the wound that had higher phloem moisture contents. Larvae showed higher survival and dry weights in phloem with low terpene contents. Adults oviposited in phloem with lower stilbene glucoside contents. Phloem moisture differed at sites around the wound compared with that at a control site away from the wound, and the nitrogen content of entire bark cores was higher above wounds than at control sites away from the wounds. Phloem moisture correlated with the nitrogen content of entire bark. Phloem terpene contents correlated with each other, as did the stilbene contents. Associations between the host exploitation pattern ofD. micans and the biochemistry of the host phloem are discussed in relation to preselection by adults of sites suitable for larval development.