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doi:10.1039/b009025p

Cited by 42 publications

(5 citation statements)

References 262 publications

(276 reference statements)

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“…Another possible reason for misclassification with any model might be that the new instances, which are to be tested, lie far away from the prediction space. Although the models presented herein are aimed at a specific class of secondary metabolites, i.e., STLs, the problem is still present since several novel STLs are reported each year, − some of them with rather unusual structures, including for example dimers . This was what we examined in turn.…”

Section: Discussionmentioning

confidence: 98%

“…Data Sets. The structures of the 921 STLs and the information concerning their taxonomic origin were taken from comprehensive surveys published in the literature. ,− The taxa (tribes and genera) presented herein are in accordance to the division made by Bremer . This information was used to assign all chemical structures to their corresponding taxa.…”

Section: Methodsmentioning

confidence: 99%

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Sesquiterpene Lactones-Based Classification of the Family Asteraceae Using Neural Networks and k-Nearest Neighbors

Hristozov

Costa

Gasteiger

2006

J. Chem. Inf. Model.

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In a recent publication we described the application of an unsupervised learning method using self-organizing maps to the separation of three tribes and seven subtribes of the plant family Asteraceae based on a set of sesquiterpene lactones (STLs) isolated from individual species. In the present work, two different structure representations--atom counts (2D) and radial distribution function (RDF) (3D)--and two supervised classification methods--counterpropagation neural networks and k-nearest neighbors (k-NN)--were used to predict the tribe in which a given STL occurs. The data set was extended from 144 to 921 STLs, and the Asteraceae tribes were augmented from three to seven. The k-NN classifier with k = 1 showed the best performance, while the RDF code outperformed the atom counts. The quality of the obtained model was assessed with two test sets, which exemplified two possible applications: (1) finding a plant source for a desired compound and (2) based on a plant species chemical profile (STLs): (a) study the relationship between the current taxonomic classification and plant's chemistry and (b) assign a species to a tribe by majority vote. In addition, the problem of defining the applicability domain of the models was assessed by means of two different approaches-principal component analysis combined with Hotelling T2 statistic and an a posteriori probability-based rule.

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Section: Discussionmentioning

confidence: 98%

Section: Methodsmentioning

confidence: 99%

Sesquiterpene Lactones-Based Classification of the Family Asteraceae Using Neural Networks and k-Nearest Neighbors

Hristozov

Costa

Gasteiger

2006

J. Chem. Inf. Model.

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“…Black peppercorns from Piper nigrum are known to have a complex flavor based on more than a dozen identified compounds ( − ). In an early study of black pepper oil, Pangborn et al () found three gas chromatography (GC) elution windows that had a distinct aroma of ground black pepper and noted that these areas also contained α- trans -bergamotene, α- cis -bergamotene, and santalene, which are sesquiterpenes that can be commonly found among plant volatiles ( − ). However, to date the role of these compounds from peppercorns for the ‘black pepper' aroma in wine remains to be established.…”

Section: Introductionmentioning

confidence: 99%

Identification and Quantification of a Marker Compound for ‘Pepper' Aroma and Flavor in Shiraz Grape Berries by Combination of Chemometrics and Gas Chromatography−Mass Spectrometry

Parker

Pollnitz

Cozzolino

et al. 2007

J. Agric. Food Chem.

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'Black pepper' aroma and flavor is important to some Australian Shiraz red wine styles but the aroma compounds involved have yet to be identified, and no objective analytical method to assess 'pepper' grape aromas is available to date. Samples of potentially 'spicy'/'peppery' grapes were obtained from vineyards in South Australia and Victoria over two vintages. The important sensory attributes of the grapes, including the aroma descriptor 'pepper', were rated by a sensory panel. The sensory study revealed a strong correlation between the intensity of 'pepper' aroma and the intensity of 'pepper' flavor perceived on the palate. The grape homogenates were analyzed by static headspace GC-MS using a cool inlet system. Vectors obtained by analysis of over 13 000 individual mass spectra per grape sample were then subjected to multivariate analyses. Both principal component analysis and partial least-squares regression were used to develop multivariate models based on mass spectra and aroma descriptors to explain the intensity of the rating of the 'pepper' character. Corresponding differences in mass spectra and aroma were observed among vineyards and from the same vineyards in different years. Additional optimization of the methodology enabled selection of a single region of the GC-MS chromatogram that allowed prediction of 'pepper' aroma intensity with a correlation coefficient >0.98 and led to the identification of alpha-ylangene, a tricyclic sesquiterpene. To assess the potential of alpha-ylangene as a marker for this sensory characteristic, a method for alpha-ylangene analysis of grapes and wine using HS-SPME-GC-MS was developed. Although not a significant aroma compound by itself, alpha-ylangene was a satisfactory marker for the 'pepper' aroma in grapes and wine, and its concentration showed similar discrimination between 'peppery' vineyards and vintages as that obtained using the multivariate models. Despite its presence in grapes, we could not detect alpha-ylangene in wine.

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“…The sesquiterpenes and sesquiterpenoids comprise a large class of natural products with diverse biological activities, including communication and defense against insects and disease . Interesting sesquiterpenes include the aphid alarm pheromone farnesene, the antiinflammatory bisabolol, the perfumery agent farnesol, and amorphadiene, a precursor to the antimalarial drug artemisinin .…”

mentioning

confidence: 99%

Metabolic Engineering to Produce Sesquiterpenes in Yeast

2003

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[reaction: see text] Presented here is a metabolically engineered yeast strain that produces sesquiterpenes. Epi-cedrol synthase expressed in a native yeast strain converted endogenous farnesyl pyrophosphate to 90 microg/L epi-cedrol. This system was genetically modified to increase foreign terpene yields to 370 microg/L. The best yields were obtained by overexpressing a truncated 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase in a upc2-1 mating type a background. This system allows sufficient production to characterize novel sesquiterpene synthase genes.

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Untitled

Cited by 42 publications

References 262 publications

Sesquiterpene Lactones-Based Classification of the Family Asteraceae Using Neural Networks and k-Nearest Neighbors

Sesquiterpene Lactones-Based Classification of the Family Asteraceae Using Neural Networks and k-Nearest Neighbors

Identification and Quantification of a Marker Compound for ‘Pepper' Aroma and Flavor in Shiraz Grape Berries by Combination of Chemometrics and Gas Chromatography−Mass Spectrometry

Metabolic Engineering to Produce Sesquiterpenes in Yeast

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