Biotransformation of constituents of essential oils by germinating wheat seed

Wheat seeds, when exposed to essential oils, are able to metabolise certain monoterpenes. The actual amounts of the compounds and their derivatives in the endosperm and embryo of wheat seeds, after exposure to the monoterpenes were determined. Neral and geranial, which are the constituents of citral, are reduced and oxidised to the corresponding alcohols and acids. Similarly citronellal, pulegone and carvacrol are converted partly to the corresponding reduction and oxidation products. The aromatic compound vanillin is partly reduced to vanillyl alcohol or oxidised to vanillic acid. In all cases it seems that part of the compounds applied are degraded, as indicated by the inability to account for all the compounds, which were supplied to the germinated seeds. In most cases the derivatives of the essential oil applied were less toxic than the parent compound. The possible role of non-specific enzymes by which the compounds are oxidised or reduced is discussed.     

Infraspecific variability in the volatile leaf oils of Chamelaucium uncinatum (Myrtaceae)

Variation in leaf essential oils and morphometric characters among 38 locations of Chamelaucium uncinatum were used to describe infraspecific diversity and geographic patterns of variation. Four chemical types were designated: citronellal, -pinene or limonene dominant, or one in which all three monoterpenes were co-dominant. The citronellal and limonene types were geographically restricted but the -pinene and co-dominant types were widespread. The citronellal type also demonstrated higher diversity (by Shannon–Weiner index) in the oil profile than the other types. Biochemical differentiation was not strongly paralleled by morphological differences between chemotypes; only the citronellal-type differed morphologically from the other three types with respect to floral bud and leaf characters. Based on biochemical and morphological differences, and geographic localization, it was concluded that the citronellal type may represent a recently evolved ecotype of C. uncinatum.     

Repellency of essential oils and their components to the human body louse, Pediculus humanus humanus

Five essential oils and nine of their components were compared to diethyl toluamide (DEET) for their repellent activity against the human body louse, Pediculus humanus humanus. The absolute or intrinsic repellency of the compounds was tested by applying the repellent to corduroy patches and comparing them with untreated patches. It was found that the most effective repellents were DEET and citronella, whose activity lasted at least 29 days. The activity of rosemary lasted at least 18 days and that of eucalyptus more than 8 days. The repellent activity of the oil components such as citronellal and geraniol lasted more than 15 and 8 days, respectively. DEET remained effective at a dilution of 1:32, geraniol at 1:8, citronella at 1:4 and rosemary and citronellal at 1:1. The comparative or standard repellency of the candidate repellents was examined with the aid of a new screening technique using hairs treated with ammonium bicarbonate which is attractive to lice. Using this technique it could be shown that the repellent activity of citronella and geraniol lasted 2 days and that of rosemary and citronellal for only one day. DEET was active for less than one day. Serial dilutions of these substances also revealed that citronella was the most potent repellent for lice, followed by citronellal, rosemary, geraniol and DEET. The differences however, were not significant.     

Synthesis and absolute configuration of optically pure enantiomers of a kappa-opioid receptor selective agonist

The enantiomers of U50,488, ligands highly selective for kappa-opioid receptors, have been prepared by a refined procedure and their optical purity demonstrated. The absolute configuration of (+)-trans-2-pyrrolidinyl-N-methylcyclohexylamine, a chemically versatile intermediate for synthesis of analogs of kappa-opioid receptor ligands with defined chirality, has been determined to be 1S,2S by X-ray crystallographic analysis. This intermediate has been used to synthesize the optically pure U50,488 enantiomers with known absolute configuration.     

香茅精油对桔小实蝇产卵驱避作用及其化学成份分析

研究了香茅Cymbopogon nardus精油对桔小实蝇Bactrocera dorsalis (Hendel)的产卵驱避作用及其化学成分。结果表明,香茅精油对桔小实蝇产卵具有一定的驱避作用,不同浓度香茅精油处理芒果上的产卵量均显著低于对照,且随着香茅精油浓度的提高其产卵量逐渐减少,当浓度为10000μg/mL时,产卵驱避率为70.06%。采用气相色谱—质谱联用(GC-MS)技术分析了香茅精油的化学成份,结果发现该精油挥发物中含量较高的是3-蒈烯,香茅醛,香叶醇,香茅醇,柠檬烯。     

Synthesis,HPLC Enantioresolution,and X‐ray Analysis of a New Series of C5‐methyl Pyridazines as N‐Formyl Peptide Receptor (FPR) Agonists

The synthesis of three racemates and the corresponding non‐chiral analogues of a C5‐methyl pyridazine series is described here, as well as the isolation of pure enantiomers and their absolute configuration assignment. In order to obtain optically active compounds, direct chromatographic methods of separation by HPLC‐UV were investigated using four chiral stationary phases (CSPs: Lux Amylose‐2, Lux Cellulose‐1, Lux Cellulose‐2 and Lux Cellulose‐3). The best resolution was achieved using amylose tris(5‐chloro‐2‐methylphenylcarbamate) (Lux Amylose‐2), and single enantiomers were isolated on a semipreparative scale with high enantiomeric excess, suitable for biological assays. The absolute configuration of optically active compounds was unequivocally established by X‐ray crystallographic analysis and comparative chiral HPLC‐UV profile. All compounds of the series were tested for formyl peptide receptor (FPR) agonist activity, and four were found to be active, with EC₅₀ values in the micromolar range. Chirality 25:400–408, 2013. © 2013 Wiley Periodicals, Inc.     

Screening of antibacterial activities of twenty-one oxygenated monoterpenes

Plant essential oils are widely used as fragrances and flavours in the cosmetic, perfume, drug and food industries. Oxygenated monoterpenes are widespread components of the essential oils, usually occurring in high amount. In this paper, the antibacterial activities of twenty-one oxygenated monoterpenes (borneol, borneol acetate, camphor, carvone, 1,8-cineole, citronellal, beta-citronellol, dihydrocarvone, fenchol, fenchone, geraniol acetate, isomenthol, limonene oxide, linalool, linalool acetate, nerol, nerol acetate, terpinen-4-ol, alpha-terpineol, menthol and menthone) and penicillin (standard antibiotic) were determined using a disc diffusion method (in vitro) against 63 bacterial strains, belonging to 37 different genera and 54 species (plant, food and clinic origins). The results showed that the oxygenated monoterpenes exhibited a variable degree of antibacterial activities. These compounds also inhibited the growth of bacterial strains by producing a weak zone of inhibition from 7 to 11 mm in diameter, depending on the susceptibility of the tested bacteria. Among the tested compounds, nerol, linalool alpha-terpineol, fenchol and terpinen-4-ol showed antibacterial activity at a broad spectrum. However, their antibacterial activities were lower than those of penicillin. In contrast to these compounds, camphor and 1,8-cineole exhibited no inhibition effects on the growth of all tested bacteria.     

Susceptibility of the bruchid Callosobruchus maculatus (Coleoptera: Bruchidae) and its parasitoid Dinarmus basalis (Hymenoptera: Pteromalidae) to three essential oils

The bruchid Callosobruchus maculatus (F.) causes major losses during the storage of seeds of Vigna unguiculata (Walp.) in West Africa. An endemic parasitoid, the pteromalid Dinarmus basalis (Rond.) reduces the increase in bruchid populations in stores and could be used for biological control. African farmers often introduce essential oils into granaries at harvest time. In Togo, essential oils were extracted from two Gramineae, Cymbopogon nardus (L.) and Cymbopogon schoenanthus (L.) and from a Lamiaceae, Ocimum basilicum (L.). The major components of these essential oils were citronellal in C. nardus, carene-2 and piperitone in C. schoenanthus and estragol in O. basilicum. Cymbopogon schoenanthus was the most toxic oil for C. maculatus adults. D. basalis adults were more susceptible to the three essential oils than the adults of their hosts C. maculatus. In the presence of cowpea seeds, the LC50s of the three essential oils were lower than in their absence, suggesting that the seeds may absorb a part of the volatiles. High doses of three essential oils slightly affected the survival of the fourth instar or the pupae of C. maculatus. This high survival was due to protection of larvae from volatiles by the surrounding seeds. The D. basalis were more affected by the oil volatiles than their hosts. Sub-lethal doses of essential oils reduced the duration of the adult life of both insect species and fecundity of the females. The differences in sensitivity of the host and its parasitoid could influence their population dynamics. The introduction of the essential oils into storage systems potentially could reduce density of parasitoid populations and increase seed losses.     

Methods to increase enantioselectivity of lipases and esterases

Lipases and esterases are frequently used in the synthesis of optically pure compounds; however, natural enzymes do not always show sufficiently high enantioselectivity. Variation of the structure of the substrates, modification of the reaction system or protein engineering (e.g. the expression of pure enzymes, rational design or directed evolution) are strategies that can be employed to improve the distinction between two enantiomers or enantiotopic groups.     

Bioactivity of selected essential oils and some components on Listeria monocytogenes biofilms

Listeria monocytogenes is a Gram-positive bacterium, able to survive and grow in water, soil, agricultural products, various foods and the food-processing environment. The ubiquitous nature of the organism, coupled with its ability to colonise food-processing surfaces by forming biofilms, causes it to be of a major concern to the industry. Increased foodborne pathogen resistance and negative consumer perceptions regarding the use of synthetic bacteriocides, has resulted in natural antimicrobials being sourced from the plant kingdom. The listerial antibiofilm activities of Syzygium aromaticum (clove), Mentha spicata (spearmint), Lippia rehmannii and Cymbopogon citratus (lemongrass) essential oils and their major components were evaluated using the crystal violet assay and confocal scanning laser microscopy. Listerial biofilms treated with S. aromaticum or M. spicata essential oils, or the pure compounds nerol and citral, exhibited a similar biofilm biomass to the positive control. However, the essential oils of lemongrass, L. rehmannii, eugenol and R-carvone caused biofilm enhancement, rather than inhibition. L. rehmannii and lemongrass essential oils did not display any antibiofilm properties. Results obtained were confirmed by microscopic observations indicating either a reduction (inhibition) or an increase (enhancement) in biofilm biomass when exposed to the essential oils or pure compounds. The present study revealed that M. spicata and S. aromaticum essential oils as well as pure citral and nerol are good candidates for further development of ecofriendly disinfectants.     

Release,Regeneration and Mutant Induction of Pleurotus cornucopiae (‘Tamogitake’) Protoplasts

Both enantiomers of aliphatic and aromatic cyanohydrins were hydrolyzed with the aid of Rhodococcus butanica ATCC 21197 to afford optically active α-hydroxy acids. The usefulness of this reaction is demonstrated by the synthesis of optically pure (R)-4-dodecanolide, a defensive secretion of rove beetles, starting from (R)-2-hydroxydecanenitrile.     

Characterization of volatile constituents of Scaligeria tripartita and studies on the antifungal activity against phytopathogenic fungi

The chemical composition of the essential oils obtained from stems and leaves, fruits and roots of Scaligeria tripartita oil was analyzed by gas chromatography-mass spectrometry. A total of 38 compounds were identified ranging 89-94% of the oil samples. Geijerene was found as a main compound in the oils of the stems and leaves (37%) and fruits (55%), whereas epoxypseudoisoeugenol angelate (37%) was found as a main compound in the root oil. Oils were subsequently evaluated for their antimalarial, antimicrobial against human pathogenic bacteria or fungi and antifungal activities against plant pathogens. Antifungal activity of Scaligeria oils was observed against the strawberry anthracnose-causing fungal plant pathogens Colletotrichum acutatum, C. fragariae and C. gloeosporioides using the direct overlay bioautography assay. Chemotaxonomically important pure compounds indicated in the bioautography assay were subsequently evaluated in a 96-well microdilution broth assay. The performance of overpressured layer chromatography (OPLC) and TLC for the analysis of Scaligeria essential oils was also compared.     

Antifungal activity of volatile compounds generated by essential oils against fungi commonly causing deterioration of bakery products

AIMS: To investigate the volatile fractions of 16 essential oils for activity against the more common fungi causing spoilage of bakery products, Eurotium amstelodami, E. herbariorum, E. repens, E. rubrum, Aspergillus flavus, A. niger and Penicillium corylophilum. METHODS AND RESULTS: The study applied 50 microl of pure essential oils in a sterilized filter paper, were carried out at pH 6 and at different water activity levels (0.80-0.90). First, a wheat flour based agar medium was used, where cinnamon leaf, clove, bay, lemongrass and thyme essential oils where found to totally inhibit all microorganisms tested. These five essential oils were then tested in sponge cake analogues, but the antifungal activity detected was much more limited. CONCLUSION: Five essential oils showed potential antifungal capacity against all species tested, over a wide range of water availability. Their activity, however, seems to be substrate-dependent. More research is needed to make them work in real bakery products, as in the preliminary study limited effectiveness was found. SIGNIFICANCE AND IMPACT OF THE STUDY: The potential of the cinnamon leaf, clove, bay, lemongrass and thyme essential oils against species belonging to Eurotium, Aspergillus and Penicillium genus has been demonstrated.     

Antimicrobial activity of essential oils and structurally related synthetic food additives towards selected pathogenic and beneficial gut bacteria

AIMS: To assess the potential of essential oils and structurally related synthetic food additives in reducing bacterial pathogens in swine intestinal tract. METHODS AND RESULTS: The antimicrobial activity of essential oils/compounds was measured by determining the inhibition of bacterial growth. Among 66 essential oils/compounds that exhibited > or =80% inhibition towards Salmonellatyphimurium DT104 and Escherichia coli O157:H7, nine were further studied. Most of the oils/compounds demonstrated high efficacy against S. typhimurium DT104, E. coli O157:H7, and E. coli with K88 pili with little inhibition towards lactobacilli and bifidobacteria. They were also tolerant to the low pH. When mixed with pig cecal digesta, these oils/compounds retained their efficacy against E. coli O157:H7. In addition, they significantly inhibited E. coli and coliform bacteria in the digesta, but had little effect on the total number of lactobacilli and anaerobic bacteria. CONCLUSIONS: Some essential oils/compounds demonstrated good potential, including efficacy, tolerance to low pH, and selectivity towards bacterial pathogens, in reducing human and animal bacterial pathogens in swine intestinal tract. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has identified candidates of essential oils/compounds for in vivo studies to develop antibiotic substitutes for the reduction of human and animal bacterial pathogens in swine intestinal tract.     

Essential oil chemotypes of Aloysia citrodora (Verbenaceae) in Northwestern Argentina

Chemical biodiversity of essential oils of natural populations of Aloysia citrodora Palau (“lemon verbena”, “cedrón”) in Northwestern Argentina was assessed by collecting in the same sites through different years. A total of 36 samples were collected in the Provinces of Salta (El Maray, La Paya, El Sunchal, El Alisal, Chorrillos), Jujuy (Chilcayo, San Roque), Catamarca (Mutquin, Colana) and Tucumán (Amaicha del Valle) in Argentina.Essential oils were obtained by hydrodistillation (Clevenger) of naturally air-dried plant material. Yields ranged from 0.16% to 1.93% (v/w), being the highest those of the collections of Mutquin. More than 65 compounds were identified by CG-FID-MS. Only 19 of these constituents, accounting from 77.3 to 98.9% of the total oil, present in more than 4.0% in at least one sample, were considered as variables for statistical analysis. Agglomerative Hierarchical Cluster analysis was conducted, showing at 65% of similarity, five groups. This grouping was in direct accordance to the biosynthetic pathways of main compounds (chemotypes).In the two sites of Jujuy, 21 collections evidenced four different chemotypes, named after the dominant component as follows: thujones, citronellal, carvone, and citral (neral + geranial). In the populations of Salta and Catamarca, linalool appeared as a new different chemotype.Though cedron is considered as a citral-bearing plant, curiously, in the 36 samples collected in the NW of Argentina, only two samples contained citral as main constituent. On the other hand, a dominance of citronellal and thujones compositions were found in the bulk of the samples collected, while others had very high content of linalool or carvone and its derivatives. Northwestern Argentina has repeatedly been mentioned as the center of biodiversity of this species.The new evidences found on the chemical biodiversity of essential oils of Aloysia citrodora in natural populations in this region, reinforce firmly this idea.     

Bi-directional chiral inversion of ketoprofen in CD-1 mice

The R enantiomers of some of the 2-arylpropionic acid non-steroidal antiinflammatory drugs (NSAIDs) are known to undergo metabolic chiral inversion to their more pharmacologically active antipodes. This process is drug and species dependent and usually unidirectional. The S to R chiral inversion, on the other hand, is rare and has been observed, in substantial extents, only for ibuprofen in guinea pigs and 2-phenylpropionic acid in dogs. After i.p. administration of single doses of racemic ketoprofen or its optically pure enantiomers to male CD-1 mice and subsequent study of the concentration time-course of the enantiomers, we noticed substantial chiral inversion in both directions. Following racemic doses, no stereoselectivity in the plasma-concentration time courses was observed. After dosing with optically pure enantiomer, the concentration of the administered enantiomer predominated during the absorption phase. During the terminal elimination phase, however, the enantiomers had the same concentrations. Our observation is suggestive of a rapid and reversible chiral inversion for ketoprofen enantiomers in mice. Chirality 9:29–31, 1997. © 1997 Wiley-Liss, Inc.     

Contact toxicity, feeding reduction, and repellency of essential oils from three plants from the ginger family (Zingiberaceae) and their major components against Sitophilus zeamais and Tribolium castaneum

The essential oils from rhizomes of Alpinia conchigera Griff, Zingiber zerumbet Smitt, Curcuma zedoaria (Berg.) Roscoe; their major compounds (camphene, camphor, 1,8-cineole, alpha-humulene, isoborneol, alpha-pinene, beta-pinene and terpinen-4-ol); and synthetic essential oils comprised of mixtures of major pure compounds in the same ratios as the extracted essential oils were tested for contact, feeding reduction, and repellency against Sitophilus zeamais Motschulsky and Tribolium castaneum (Herbst) adults. Via topical applications, the three extracted oils had similar toxicity against S. zeamais (LD50 fiducial limits: 18-24 microg oil/mg insect). T. castaneum had similar sensitivity to all three oils (35-58 microg/mg), and it was less sensitive than S. zeamais. The LD50 values of synthetic A. conchigera and synthetic Z. zerumbet oils were similar to those of their corresponding extracted essential oils. The synthetic C. zedoaria oils showed lower contact toxicity than the extracted C. zedoaria oils to both insects. Sitophilus zeamais and T. castaneum were sensitive to terpinen-4-ol and isoborneol in contact toxicity tests. In antifeedant tests, the three extracted oils were able to decrease the consumption of flour disks, especially Z. zerumbet oils, whereas both insect species could feed on the flour disks treated with three synthetic essential oils. Only terpinen-4-ol deterred feeding in both insects. In repellency tests, A. conchigera oils at highest concentration repelled S. zeamais and T. castaneum. None of the synthetic essential oils repelled S. zeamais (315 microl/cm2) and T. castaneum (31 microl/cm2) Only terpinen-4-ol showed repellent activity against both insects.     

A novel and facile preparation of bremazocine enantiomers through optically pure N-norbremazocines

In order to provide ready access to multigram quantities of the optically pure bremazocines [(-)- and (+)-9,9-dimethyl-5-ethyl-2-hydroxy-2-(1-hydroxy-cyclopropylmethyl)-6,7-benzomorphan)], we have developed an improved non-chromatographic synthesis, and determined the optical purity of their N-nor precursors using a rapid and relatively simple 1H NMR method based on diastereomeric derivatization with optically pure 1-phenylethylisocyanate. This method of determining optical purity should be readily amenable to similar systems containing phenolic amino functionalities. Finally, a greatly simplified methodology for introduction of the N-(1-hydroxycyclopropylmethyl) substituent in bremazocine is described. The improved synthetic method-the overall yield was increased about 3-fold-combined with the practical methodology to determine optical purity will considerably facilitate the employment of these enantiomers as pharmacological tools for examination of the kappa-opioid receptor system, as well as their evaluation as drug abuse treatment agents. This synthesis will also enable the study of these enantiomers for other, non-classical applications (e.g., treatment agents for HIV).     

Application of lipase-catalyzed transformations for the synthesis of insect pheromones and related compounds

This review describes efficient means of preparing optically pure insect pheromones and related compounds via lipase-catalyzed enantioselective reaction on a large scale. (1) A new synthesis of the Japanese beetle pheromone, (R,Z)-(−)-5-(1-decenyl)oxacyclopentan-2-one, established by a combination of two lipase-catalyzed transformation was demonstrated. (2) A chemico-enzymatic procedure for the syntheses of both enantiomers of cupreous chafer beetle pheromone, (R,Z)- and (S,Z)-5-(1-octenyl)oxacyclopentan-2-one, was described. (3) An optical resolution of (±)-2,3-epoxy-8-methyl-1-nonanol, the key intermediate of the synthesis of gypsy moth pheromone, was demonstrated. (4) A practical chemico-enzymatic synthesis of (+)-disparlure in large scale was demonstrated. (5) A facile synthesis of carboxyalkyl acrylate, which is special monomers in the synthesis of the new polymers, by two lipase-catalyzed regioselective reactions was described.     

Resolution and absolute configuration of some α-aminoacetals: en route to enantiopure N-protected α-aminoaldehydes

The first successful resolution of rac-α-aminoacetals via diastereoisomeric salt formation with optically pure N-protected aminoacids is reported. The absolute configuration assignment of α-aminoacetal enantiomers is performed by an entirely non-racemizing chemical correlation method involving N-protection and a new efficient hydrolysis step followed by a reduction of the resulting N-protected α-aminoaldehyde intermediates. A racemization method of optically enriched α-aminoacetals is exemplified to allow valorisation of both enantiomers.