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At least 955 records · Page 53Linked to original sources
PubMed2002

Phytochemical induction by herbivores could affect quality of essential oils from aromatic plants.

Plant tissues may show chemical changes following herbivory. In aromatic plants such changes could affect the specific compounds on which commercial exploitation is based. This possibility was analyzed for Mintosthachys mollis, a member of the Lamiaceae native to Central Argentina with medicinal and aromatic uses in the region, and two types of insect herbivores: a leaf miner and a gall insect. Analysis of the essential oils of mined/undamaged leaves, as well as leaves from stems with and without galls, revealed changes in concentrations of the two main monoterpenes. A decrease in pulegone concentration was associated with both types of insect damage, whereas menthone increased significantly only in mined leaves. Inducible chemical changes in aromatic and medicinal plants may be common and widespread; their economic implications deserve investigation.

Animals↗
PubMed2002

Characterization of essential oils from lamiaceae species by fourier transform Raman spectroscopy.

The Fourier transform Raman (FT-Raman) spectra of pure terpenes and essential oils obtained by hydrodistillation of some Lamiaceae species, are presented. This study shows that principal components of an essential oil can be recognized by FT-Raman. Components predicted by FT-Raman spectrum of an essential oil correlate well with those found as major constituents by GC-MS. In this way the basic chemical character of an essential oil can be recognized. The results demonstrate that certain Raman intensities can be correlated to specific terpenes and therefore FT-Raman can discriminate between the essential oils of which main components belong to different classes of compounds.

Acyclic Monoterpenes↗
PubMed2005

Quantitative variations in the essential oil of Minthostachys mollis (Kunth.) Griseb. in response to insects with different feeding habits.

Plants display a diverse array of inducible changes in secondary metabolites following insect herbivory. Herbivores differ in their feeding behavior, physiology, and mode of attachment to the leaf surface, and such variations might be reflected in the induced responses of damaged plants. Induced changes were analyzed for Minthostachys mollis, a Lamiaceae with medicinal and aromatic uses, and four species of folivore insects with different feeding habits (chewing, scraping, sap-sucking, and puncturing). In M. mollis leaves experimentally exposed to the insects, levels of the two dominant monoterpenes pulegone and menthone were assessed 24 and 48 h after wounding. Menthone content generally decreased in the essential oil of damaged leaves, whereas pulegone concentration increased in all treatments. These changes occurred also in the adjacent undamaged leaves, suggesting a systemic response. The relatively uniform response to different kinds of damage could be attributable to the presence of such a strongly active compound as pulegone in the essential oil of M. mollis. The effects of wounding on essential oil concentration may be significant from a commercial point of view.

Animals↗
PubMed1999

Transformation of a monoterpene ketone, (R)-(+)-pulegone, a potent hepatotoxin, in Mucor piriformis.

Biotransformation of a monoterpene ketone, (R)-(+)-pulegone (I), a potent hepatotoxin, was studied using a fungal strain, Mucor piriformis. Eight metabolites, namely, 5-hydroxypulegone (II), piperitenone (III), 6-hydroxypulegone (IV), 3-hydroxypulegone (V), 5-methyl-2-(1-hydroxy-1-methylethyl)-2-cyclohexene-1-one (VI), 3-hydroxyisopulegone (VII), 7-hydroxypiperitenone (VIII), and 7-hydroxypulegone (IX), have been isolated from the fermentation medium and identified. GC analysis of the metabolites indicated that II was the major metabolite formed. The organism initiates transformation either by hydroxylation at the C-5 position or by hydroxylation of the ring methylenes, the former being the major activity. On the basis of the identification of the metabolites, pathways for the biotransformation of (R)-(+)-pulegone have been proposed. The mode of transformation of (S)-(-)-pulegone by this organism was shown to be similar to that of its (R)-(+)-enantiomer. When isopulegone (X) was used as the substrate, the organism isomerized it to pulegone (I), which was then transformed to metabolites II-IX.

Animals↗
PubMed1999

Enantiomeric purity and odor characteristics of 2- and 3-acetoxy-1, 8-cineoles in the rhizomes of Alpinia galanga willd.

(S)-(+)-O-methylmandelate esters of trans- and cis-1,3, 3-trimethyl-2-oxabicyclo[2.2.2]octan-5- and 6-ols (2- and 3-hydroxy-1,8-cineoles) were prepared, and eight diastereomers were separated. The absolute configuration of the asymmetric carbons of the cineole moiety of each diastereomer was determined by (1)H NMR data according to the Mosher theory. Each mandelate was reduced with LiAlH(4) to obtain optically pure hydroxy-1,8-cineoles, this being followed by acetylation to afford optically pure acetoxy-1, 8-cineoles. These acetates were subjected to chiral GC, using a cyclodextrin column, and the enantiomeric purity of trans- and cis-1, 3,3-trimethyl-2-oxabicyclo[2.2.2]octan-5- and 6-yl acetates in the aroma concentrate from the rhizomes of Alpinia galanga was determined as 93.9 (5S), 19.4 (5R), 63.5 (6R), and 100 (6R) % ee, respectively. The aroma character of each enantiomer was also evaluated by GC-sniffing.

Aluminum Compounds↗
PubMed1999

Effect of sucrose on the perceived flavor intensity of chewing gum.

The release of sucrose and menthone from chewing gum was measured in-mouth and in-nose, respectively, during eating. Swabs of saliva were taken from the tongue and analyzed using a rapid, direct liquid-mass spectrometry procedure. Menthone concentration in-nose was monitored on a breath-by-breath basis using direct gas phase atmospheric pressure chemical ionization-mass spectrometry. Simultaneously with the volatile release, trained panelists followed the change in mint flavor by time-intensity (TI) analysis. Two types of commercial chewing gum were analyzed. Both showed that the panelists perception of mint flavor followed sucrose release rather than menthone release. The temporal analysis of the chemical stimuli, with simultaneous TI analysis, provided unequivocal evidence of the perceptual interaction between nonvolatile and volatile flavor compounds from chewing gum.

Breath Tests↗
PubMed1999

Biogenetic studies in Mentha x piperita. 2. Stereoselectivity in the bioconversion of pulegone into menthone and isomenthone.

Mentha x piperita shoot tips and first leaf pairs were fed with aqueous solutions of different deuterium-labeled pulegone and various enantiomeric distributions. The essential oil was extracted by solid-phase microextraction and analyzed using enantioselective multidimensional gas chromatography/mass spectrometry. The genuine p-menthan-3-ones (-)-menthone and (+)-isomenthone as well as their labeled analogues were analyzed simultaneously. Both enantiomers of labeled pulegone were converted into the corresponding labeled p-menthan-3-ones by Mentha x piperita, indicating an unspecific reduction process. The generation of 4S- and 4R-configured p-menthan-3-ones differed in their stereoselectivities. Labeled (S)-pulegone was reduced by Mentha x piperita more rapidly rather than (R)-pulegone. From a comparison of labeled pulegone enantiomers the bioconversion preferrably led to 4S-configured diastereomers.

Biotransformation↗
PubMed1999

Biosynthesis of menthofuran in Mentha x piperita: stereoselective and mechanistic studies.

Mentha x piperita shoot tips and first leaf pair were fed with aqueous solutions of [(2)H(2)]- and [(2)H(2)]/[(18)O]-labeled pulegone. The essential oil was analyzed by solid phase microextraction and enantioselective multidimensional gas chromatography/mass spectrometry. After feeding experiments with labeled pulegone racemate, both labeled (S)-menthofuran and (R)-menthofuran were detectable simultaneously together with genuine (R)-menthofuran. It could be shown that both labeled pulegone enantiomers are converted by Mentha x piperita to the corresponding labeled menthofuran enantiomers, favoring the labeled analogue of the nongenuine (S)-pulegone. The oxygen in menthofuran is introduced by enzymatic oxidation of pulegone, as concluded from feeding experiments with mixed labeled [(2)H(2)]/[(18)O]pulegone.

Cyclohexane Monoterpenes↗
PubMed2001

Highly diastereoselective synthesis of vinylcyclopropane derivatives with (-)-8-phenylmenthol as chiral auxiliary.

The silylated telluronium allylide 4, generated in situ from the corresponding telluronium salt in the presence of LiTMP, reacted with (-)-8-phenylmenthyl alpha,beta-unsaturated esters to afford trans-2-silylvinyl-trans-3-substituted cyclopropyl esters with high diastereoselectivity in high yields. The absolute configuration was determined by chemical transformation. A mechanistic rationale is proposed.

Cyclohexanes↗
PubMed2001

Chiral auxiliaries for asymmetric radical cyclization reactions: application to the enantioselective synthesis of (+)-triptocallol.

[figure: see text] A series of epimeric 8-aryl menthyl derivatives 5a-d and 6a-l, prepared from the same chiral source (R)-pulegone, were employed as chiral auxiliaries in the asymmetric radical cyclization reactions of beta-keto esters mediated by Mn(OAc)3. Chiral precursors 8c and 8d provided the cyclization products 10c and 10d, respectively, as single isomers (dr > 99:1), whereas the cyclization of precursor 9k gave 13k with good stereoselectivity (dr = 24:1). Diastereomer 13e was employed as the key intermediate in the enantioselective synthesis of (+)-triptocallol in 90% ee.

Biological Factors↗
PubMed2001

Synthetic studies of the HIV-1 protease inhibitive didemnaketals: stereocontrolled synthetic approach to the key mother spiroketals.

The stereocontrolled synthesis of (2S,4R,6R,8S,10S,1'R,1' 'R)-2(acetylhydroxymethyl)-4,10-dimethyl-8(isopropenylhydroxymethyl)-1,7-dioxaspiro[5,5]undecane (4a) and its C1' '-epimer (4b), the key mother spiroketals of the HIV-1 protease inhibitive didemnaketals from the ascidian Didemnum sp., has been carried out through multisteps from the natural (R)-(+)-pulegone, which involved the diastereoselective construction of four chiral carbon centers(C-2, C-6, C-8, and C-1') by intramolecular chiral induce.

Animals↗
PubMed2001

Chiral auxiliary based approach toward the synthesis of C-glycosylated amino acids.

[reaction in text] In a chiral auxiliary based method C-glycosylated amino acids can be obtained by a 1,3-dipolar cycloaddition of a chiral glycine equivalent and C-1 allyl- or vinyl-derived carbohydrate building blocks as the key step. The products are formed regio- and diastereoselectively. Reductive cleavage of the N-O bond of the isoxazolidine and of the chiral auxiliary leads to C-glycosylated amino acids. The use of (-)-menthone to (+)-menthone as the auxiliary leads to the corresponding diastereomers.

Amino Acids↗
PubMedDate not supplied

Metabolic activation of (R)-(+)-pulegone to a reactive enonal that covalently binds to mouse liver proteins.

Pulegone, a naturally occurring hepatotoxin, is metabolically activated to chemically reactive intermediates that are capable of covalent binding to cellular protein. Studies in vivo and in vitro with inhibitors and inducers of cytochrome P-450 demonstrated an association among the hepatocellular toxicity of pulegone and its metabolic activation and covalent binding to protein. The exocyclic double bond of pulegone apparently is an important structural feature in the activation mechanism and binding to protein inasmuch as the reduced analogue, menthone, is neither hepatotoxic nor does it bind extensively to tissue proteins. Preliminary studies using semicarbazide as a trapping agent indicate that an unsaturated gamma-ketoaldehyde is the ultimate chemically reactive metabolite of pulegone.

Alkylation↗
PubMedDate not supplied

Reactive intermediates in the oxidation of menthofuran by cytochromes P-450.

Menthofuran, a naturally occurring hepatotoxin, is metabolically activated to chemically reactive intermediates that are capable of covalent binding to cellular proteins. Studies in vivo and in vitro with inhibitors and inducers of hepatic cytochromes P-450 demonstrated an association between hepatocellular damage caused by menthofuran and its metabolic activation and covalent binding to target organ proteins. The same gamma-ketoenal formed from the metabolic precursor of menthofuran, pulegone, is the major electrophilic metabolite of menthofuran as well. Diastereomeric mintlactones also are formed, and studies with H218O and 18O2 indicate that the gamma-ketoenal is a precursor to the mintlactones, as well as other reactive intermediates in the cytochrome P-450 mediated oxidation of menthofuran.

Acetaminophen↗
PubMed2001

1,8-cineol, a food flavoring agent, prevents ethanol-induced gastric injury in rats.

This study investigated the gastroptrotective effect of 1,8-cineole (cineole) on ethanol-induced gastric mucosal damage in rats and the possible mechanisms involved. 1,8-Cineole (50-200 mg/kg), given orally 1 hr before administration of 1 ml of absolute ethanol significantly attenuated the ethanol-induced gastric injury in a manner similar to nordihydroguairetic acid, a known lipoxygenase inhibitor. 1,8-Cineole showed a tendency to restore the ethanol-associated decreases in nonprotein sulfhydryls, suggesting a possible antioxidant effect. In gastric secretion studies, 1,8-cineole, similar to cimetidine, a known histamine-2 receptor antagonist, demonstrated significant inhibitions of both gastric juice volume as well as total acid output. The protection offered by 1,8-cineole was found to be unaltered by 8-phenyltheophylline or L-NAME, indicating that its effect is not mediated by endogenous adenosine or nitric oxide. These results, taken together with the earlier reports, suggest that the antioxidant and lipoxygenase inhibitory actions of 1,8-cineole are of prime importance in affording gastroprotection against ethanol injury in the rat.

Administration, Oral↗
PubMed1996

The effect of formulation on the antimicrobial activity of cetylpyridinium chloride in candy based lozenges.

PURPOSE: The purpose of this investigation was to determine the influence on the antimicrobial activity of cetylpyridinium chloride of the various components of the formulation of each of six candy based lozenges. METHODS: In vivo activity was investigated using six volunteers by determining the reduction in colony forming units recoverable from the oropharynx after sucking each lozenge separately on different days. In vitro determinations investigated the relative activity of aqueous solutions of the lozenges, the effect on activity of additional active ingredients, pH and lozenge base ingredients against separate inocula of each of the test organisms Staphylococcus aureus, Streptococcus pyogenes and Candida albicans. RESULTS: Both in vivo and in vitro results showed that the pH of the dissolved lozenge solution was the single most influential readily adjustable formulation parameter which significantly influenced the activity of cetylpyridinium chloride activity in candy based lozenges. CONCLUSIONS: Lozenges containing cetylpyridinium chloride as the active ingredient should be formulated at a pH greater than 5.5.

Administration, Oral↗