Chemotaxonomic Differentiation Research Articles

Comparative LC-MS/MS-based molecular networking, DNA fingerprinting, and in vitro anti-Helicobacter pylori activity of three Egyptian Ficus cultivars

Ficus species (Moraceae) have been used for nutrition and traditional medicine, and plants from this family are phytochemically abundant and serve as a potential source of natural products. As a result of the inherent complexity of the plant metabolomes and the fact that these Ficus species chemical space has not yet been fully decoded, it is still difficult to characterize their phytochemistry. Therefore, this study, we suggest the use of the molecular networking to elucidate the chemical classes existing in leaves of three Ficus species (F. deltoidei Jack, F. drupacea Thunb and F. sycomorus L.) and highlight the importance of molecular networking in examining their chemotaxonomy . By using computational tools, 90 metabolites were annotated , including phenolic acids, flavonoids, furanocoumarins, fatty acids and terpenoids. Phenolic acids were detected as the main class present in the three studied species. Flavonoids-C-glycosides, flavonoids-O-glycosides and isoflavonoids were mainly present in F. drupacea and F. sycomorus, while furanocoumarins were proposed in F. sycomorus. Vomifoliol-based sesquiterpenes were proposed in F. deltoidei. The chemotaxonomic differentiation agreed with the DNA fingerprinting using SCOT and ISSR markers. F. deltoidei, in particular, had a divergent chemical fingerprint as well as a different genotype. Chemotype differentiation using chemical fingerprints, in conjunction with the proposed genetic markers, creates an effective identification tool for the quality control of the raw materials and products derived from those three Ficus species. As well, F. drupacea exploited the most potent inhibition of H. pylori with MIC of 7.81 µg/ mL compared with clarithromycin. Overall, molecular networking provides a promising approach for the exploration of the chemical space of plant metabolomes and the elucidation of chemotaxonomy.

Quality control, ontogenetic variability and sensory profiling of ‘cilantro-mimic’ spiny coriander (Eryngium foetidum L.): A flavour perspective

Spiny coriander (Eryngium foetidum L.) is a cilantro-flavoured aromatic oil-bearing herb and traditional food flavouring agent. In this study, a gas chromatography-mass spectrometry technique was developed in conjunction with cluster analysis for its quality control and chemotaxonomic differentiation with common coriander. Spiny coriander was distinguished by a high ratio of fatty aldehydes versus fatty alcohols (378.5:1.0) and trans-alkenals versus alkanals (16.3:1.0) in the essential oil. A systematic investigation on its ontogenetic variability recommended the harvest of whole aerial part at full maturity to maximize the oil yield (24.6 mg/plant). Various sensory analyses established the uniqueness in its odour with more pungency (but less sweet and earthy) compared to common coriander. Volatile chemo-profiling revealed high abundance of fatty aldehydes (98.36%) over alcohols (not detected) as the chemical origin of its sensorial distinguishability. trans-2-Dodecenal, major oil constituent was found to be the key odorant and odour-mimic to this herb. The preference test demonstrated the potential of its essential oil (0.005–0.01% v/v) as a unique and readymade natural flavour in soup. Thus, the current study described an authentication technique, ontogenetic variability and sensorial profile of spiny coriander oil in reference to common coriander that may encourage its inclusion in food industries.

Chemotaxonomic Differentiation of Pinus Species Based on n-Alkane and Long-Chain Alcohol Profiles of Needle Cuticular Waxes.

n-Alkane and long-chain alcohol (LCOH) profiles of needle cuticular waxes of nine provenances of three Pinus species (P. taeda. P. pinaster and P. pinea) were determined and their chemotaxonomic importance was studied. n-Alkanes concentrations were very low in all Pinus spp. A lack of ability of these compounds to differentiate Pinus spp. and their provenances was observed. LCOH concentrations were much higher, being nonacosan-10-ol (10-C29 -OH) the most abundant one in all Pinus spp. Total LCOH concentrations varied (P<0.001) between Pinus spp. with P. taeda presenting the highest (P<0.05) value and P. pinea the lowest one. Differences in LCOH profiles were large (P<0.001) and allowed separation of Pinus spp. in the Principal Component Analysis (PCA). Although a noticeable separation of individuals was not observed. cluster analysis on LCOH concentrations allowed a clear distinction between species, indicating their potential to be used as chemotaxonomic markers to differentiate provenances of different Pinus spp.

Flavonoids and Limonoids Profiles Variation in Leaves from Mandarin Cultivars and Its Relationship with Alternate Bearing

Alternate bearing in citrus trees has been extensively studied as a key feature for citrus growers. Although the genetic and the biochemical process occurring during alternate bearing has been studied extensively, there is a lack of information identifying the presence of metabolic indicators during “on” and “off” years. In citrus plants, leaves play a central role in the metabolic pathway triggering the flowering induction process. To investigate the changes during this transition, a liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) analysis of the leaf profiles of 20 compounds (17 polyphenols, two limonoids, and one furanocoumarin), in bearing and non-bearing branches arising from four different mandarin genotypes, was performed. The same metabolites were found in all the genotypes at both stages: both limonoids and 11 polyphenols. Using these compounds, the chemotaxonomic differentiation between cultivars was assessed. The levels of flavanones and limonoids showed differences in both bearing stages and the transition from vegetative to flowering could be shown by the activation of the polyphenol biosynthetic pathway, from precursors like naringenin to metabolic end-points such as narirutin and polymethoxyflavones. Narirutin levels showed significant differences between both stages, suggesting it as a possible marker of the physiological status of the branch.

A New Flavonoid from Malaysian &lt;i&gt;Dipterocarpus cornutus&lt;/i&gt;

Dipterocarpus cornutus Dyer is commonly known as ‘keruing’. It belongs to the family of Dipterocarpaceae, an important timber family in South East Asia. D. cornutus is listed as critically endangered on IUCN Red List. Since no comprehensive study has been documented on the chemical constituents of D. cornutus, there is an urgent need to study this plant comprehensively. Phytochemical study of the stem bark of D. cornutus afforded a new flavonoid (1) and nine known compounds, which consist of flavonoids (2, 3), oligostilbenoids (4, 5, 7, 8, 9, 10), and coumarin (6). The finding of the study contributes to the chemotaxonomic differentiation in the plants of the tribe Dipterocarpae.

Chemical variability of essential oils of three subspecies of Thymus munbyanus Boiss. & Reut. from Western Algeria

ABSTRACT Chemical composition of the essential oils of three subspecies of Algerian Thymus munbyanus Boiss. & Reut. (subsp. abylaeus, subsp. ciliatus and subsp. coloratus) aerial parts have been investigated. GC and GC/MS analysis allowed the identification of sixty-eight compounds accounting for 99.3%, 99.7% and 98.2% of collective essential oils of three subspecies. The main components of three collective essential oils were: α-terpinyl acetate (51.7%), α-terpineol (9.7%), borneol (6.8%) and bornyl acetate (5.2%) for subsp. abylaeus; carvacrol (65.7%), γ-terpinene (13.6%) and p-cymene (7.9%) for subsp. ciliatus and camphor (25.9%), myrcene (16.9%), 1,8-cineole (6.5%) and camphene (6.2%) for subsp. coloratus. Intra-species variations of chemical compositions of essential oil from thirty-five Algerian samples were also investigated using statistical analysis. Essential oils samples were discriminated in three main clusters confirming relation between the chemical compositions and taxonomical differentiation between the three subspecies. These results confirm chemotaxonomic differentiation of all subspecies of T. munbyanus.

Epicuticular wax lipid composition of endemic European Betula species in a simulated ontogenetic/diagenetic continuum and its application to chemotaxonomy and paleobotany

Plants are excellent climate indicators and their macro-remains or pollen accumulating in geological archives serve as recorders of environmental change. In Europe birch trees contribute importantly to Holocene plant successions. They constitute the dwarf species Betula nana and B. humilis, representing colder and two tree birches, B. pubescens and B. pendula indicative of more temperate climate. Birch pollen is highly similar preventing species differentiation. We obtained unambiguous chemotaxonomic differentiation of four European birch species via cuticular wax lipids. Dominating lipid classes in recent epicuticular birch waxes were n-alkanes (nC23 to nC33), n-alcohols and n-alkanoic acids (nC20 to nC32), and long-chain wax ester (nC36 to nC48) differing in amount and distribution. After plant senescence and in geological archives lipids undergo diagenetic alteration modifying the distributions found in recent plants. Long-chain wax esters via hydrolysis release bound n-alcohols and n-fatty acids, adding to their free analogues. Simulated release of bound lipids increased the pool of n-alcohol and n-fatty acids up to 400%. Such modification of primary lipid patterns is unaccounted for in most paleovegetation studies. Proceeding diagenesis, e.g. by decarboxylation will convert these functionalized primary and secondary lipids into their corresponding n-alkanes, the compound class mostly applied in paleoenvironment reconstruction. The simulated n-alkane pattern changed significantly, evidenced by an increase of mid-chain (nC23,nC25) homologues. Release of bound lipids may not only alter molecular but also isotopic composition, which may cause errors in paleoclimate reconstruction. We assessed the potential contribution of secondary (free lipid decarboxylation) and tertiary (bound lipid decarboxylation) wax metabolites and compared the cumulative n-alkane patterns with birch n-alkane distributions reported in the literature. Two statistically different patterns were separated, one dominated by primary, the other by secondary and tertiary formed n-alkanes. This may explain the inconsistency in previous birch wax analysis reported and needs consideration in paleoenvironment reconstruction.

Chemotaxonomic patterns of vegetation and soils along altitudinal transects of the Bale Mountains, Ethiopia, and implications for paleovegetation reconstructions – Part II: lignin-derived phenols and leaf-wax-derived &amp;lt;i&amp;gt;n&amp;lt;/i&amp;gt;-alkanes

Abstract. Erica is a dominant vegetation type in many sub-afroalpine ecosystems, such as the Bale Mountains in Ethiopia. However, the past extent of Erica is not well known and climate versus anthropogenic influence on altitudinal shifts are difficult to assign unambiguously, especially during the Holocene. The main objective of the present study is to chemotaxonomically characterize the dominant plant species occurring in the Bale Mountains using lignin phenols and n-alkane biomarkers and to examine the potential of those biomarkers for reconstructing vegetation history. Fresh plant material, organic layer and mineral topsoil samples were collected along a northeastern and a southwestern altitudinal transect (4134–3870 and 4377–2550 m a.s.l., respectively). Lignin-derived vanillyl, syringyl and cinnamyl phenols were analyzed using the cupric oxide oxidation method. Leaf-wax-derived n-alkanes were extracted and purified using Soxhlet and aminopropyl columns. Individual lignin phenols and n-alkanes were separated by gas-chromatography and detected by mass spectrometry and flame ionization detection, respectively. We found that the relative contributions of vanillyl, syringyl and cinnamyl phenols allow us to chemotaxonomically distinguish contemporary plant species of the Bale Mountains. Erica in particular is characterized by relatively high cinnamyl contributions of &gt;40 %. However, litter degradation strongly decreases the lignin phenol concentrations and completely changes the lignin phenol patterns. Relative cinnamyl contributions in soils under Erica were &lt;40 %, while soils that developed under Poaceae (Festuca abyssinica) exhibited relative cinnamyl contributions of &gt;40 %. Similarly, long-chain n-alkanes extracted from the leaf waxes allowed for differentiation between Erica versus Festuca abyssinica and Alchemilla, based on lower C31 ∕ C29 ratios in Erica. However, this characteristic plant pattern was also lost due to degradation in the respective O layers and Ah horizons. In conclusion, although in modern-day plant samples a chemotaxonomic differentiation is possible, soil degradation processes seem to render the proxies unusable for the reconstruction of the past extent of Erica on the Sanetti Plateau, Bale Mountains, Ethiopia. This finding is of high relevance beyond our case study.

Chemotaxonomic differentiation of Clerodendrum species based on high-performance thin-layer chromatographic fingerprinting of key secondary metabolites and chemometric data analysis

Clerodendrum viscosum leaves are used in indigenous systems of medicines of mainland and maritime Southeast Asian countries for the treatment of fever, pain, dysentery, colic, and removal of Ascarids. The Clerodendrum species under study exhibit various phytochemical and morphological similarities. Therefore, it is very challenging to distinguish raw powdered materials used for therapeutic purposes. A validated high-performance thin-layer chromatography (HPTLC) method with 4 key markers, viz., 24β-ethylcholesta-5,22E,25-triene-3β-O-D-glucoside, clerodinin-A, 24β-ethylcholesta-5,22E,25-triene-3β-ol, and lupeol coupled with a chemometric analysis was used to distinguish 3 closely related Clerodendrum species, viz., C. inerme, C. multiforum, and C. viscosum. PRISMA approach was applied for effective HPTLC fingerprint development. The HPTLC—densitometry method was validated following the current International Conference on Harmonisation (ICH) guidelines. Taxonomic differentiation was established by fingerprint-based similarity analysis, a chemotaxonomic study using hierarchical clustering analysis (HCA), and principal component analysis (PCA) was done. HPTLC chromatogram similarity was calculated as correlation coefficient and congruence coefficient values, demonstrating poor similarities (0.26–0.86). However, PCA has resulted in 2 principal component (PC) loadings. PC1 separated C. multiforum, explaining 85.48% of variance mainly due to distribution of 2 triterpenoids. The present HPTLC method is coupled to marker-based quality determination of raw plants as well as discrimination of Clerodendrum species. Chemometric analysis based on 4 metabolites clearly establishes a practical identification of Clerodendrum species intended for therapeutic use.

Current knowledge of the species complex Anastrepha fraterculus (Diptera, Tephritidae) in Brazil.

The study of the species complex Anastrepha fraterculus (Af complex) in Brazil is especially important in a taxonomical, evolutionary and pest management context, because there are evidences that some of them may occur in sympatry. In this review, we analyzed the main results supporting evidences that three cryptic species occur in Brazil. The taxonomical and phylogenetic relationships based on eggshell morphology, adult morphometrics, as well as cytotaxonomy and genetic differentiations are discussed. We also review available information on sexual behavior including acoustic communication of males during courtship and sexual incompatibility; and chemical signals involved in the communication between sexes, with a special focus on sex pheromones. We examined the role of long- and short-range pheromones (male-produced volatiles and cuticular hydrocarbons, respectively), their implications in sexual isolation, and their possible use for chemotaxonomic differentiation of the putative species of the Af complex.

Distinction of four Dalbergia species by FTIR, 2nd derivative IR, and 2D-IR spectroscopy of their ethanol-benzene extractives

Abstract Four common species of Dalbergia genus (D. bariensis, D. oliveri, D. cochinchinensis, and D. retusa), which are traded as “Rosewood” or “Hongmu” commonly throughout East and Southeast Asia, were extracted with ethanol-benzene and the extractives were analyzed by means of three IR spectroscopic methods aiming at their chemotaxonomic differentiation. Conventional FTIR and 2nd derivative IR (SD-IR) showed defined spectral ranges, where the differences are pronounced. Two-dimensional correlation infrared (2D-IR) spectroscopy revealed significant auto-peaks suitable for reliable differentiation of the four Dalbergia species. The gas chromatography-mass spectrometry (GC-MS) evaluation of the extractives was also useful. It can be concluded that the analysis of the extractives is the best chemotaxonomic approach for identification of anatomically similar wood species.

Comparative analysis of bacterial community composition in bulk tank raw milk by culture-dependent and culture-independent methods using the viability dye propidium monoazide

Microbial diversity of 3 raw milk samples after 72h of storage at 4°C in a bulk tank was analyzed by culture-dependent and -independent methods. The culture-dependent approach was based on the isolation of bacteria on complex and selective media, chemotaxonomic differentiation of isolates, and subsequent identification by 16S rRNA gene sequencing. The culture-independent approach included the treatment of raw milk with the dye propidium monoazide before direct DNA extraction by mechanic and enzymatic cell lysis approaches, and cloning and sequencing of the 16S rRNA genes. The selective detection of viable bacteria improved the comparability between bacterial compositions of raw milk based on culture-dependent and -independent methods, which was the major objective of this study. Several bacterial species of the phyla Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria were detected by the culture-dependent method, whereas mainly bacteria of the phylum Proteobacteria as well as low proportions of the phyla Bacteroidetes and Actinobacteria were detected by the culture-independent method. This led to the conclusion that the phylum Firmicutes was strongly discriminated by the culture-independent approach. Generally, species richness detected by the culture-dependent method was higher than that detected by the culture-independent method for all samples. However, few taxa could be detected solely by the direct DNA-based method. In conclusion, the combination of culture-dependent and -independent methods led to the detection of the highest bacterial diversity for the raw milk samples analyzed. It was shown that DNA extraction from raw milk as the essential step in culture-independent methods causes the discrimination of taxa by incomplete cell lysis. Treatment of raw milk with the viability dye propidium monoazide was optimized for the application in raw milk without former removal of milk ingredients and proved to be a suitable tool to ensure comparability of bacterial diversity depicted by both methods.

A chemotaxonomic assessment of four indigenous South African Lippia species using GC–MS and vibrational spectroscopy of the essential oils

Lippia species are widely used as traditional remedies by many South African communities. The identification of Lippia spp. indigenous to South Africa is currently based on the morphology and geographical origin of the specimen. However, morphological similarities are evident and due to sympatric distributions, different species may co-occur in the same natural environment, thereby presenting difficulties in the taxonomic delimitation of these taxa. In this paper, gas chromatography–mass spectrometry (GC–MS) and vibrational spectroscopic analyses were used to investigate the chemotaxonomic differentiation of four Lippia species (L. javanica, L. scaberrima, L. rehmannii and L. wilmsii), based on the essential oil composition. The results demonstrate that multivariate classification of chromatographic data enabled separation of Lippia oils into three distinct clusters representing L. scaberrima, L. rehmannii and L. javanica. With the aid of chemometric algorithms, it was also possible to use both mid infrared (MIR) and near infrared (NIR) spectroscopy for a clear distinction of the Lippia spp., with results comparable to those obtained by GC–MS. Orthogonal projections to latent structures (OPLS) presented a better classification algorithm than principal component analysis (PCA), in both GC–MS and spectroscopy analyses. Chemical variations within the Lippia spp. complex were evident, particularly for L. javanica and L. scaberrima, which exhibited significant intra-species variation.

Characterization of Yew Tree (Taxus) Varieties by Fingerprint and Principal Component Analyses

The composition of varieties of Taxus growing in Estonia was analyzed by capillary electrophoresis with diode array detection (CE-DAD) for the separation of phenolic compounds, and by high performance liquid chromatography-mass spectrometry (HPLC-MS) for the determination of taxoids. The main purpose of this study was the chemotaxonomic differentiation of varieties of Taxus by using data from these analyses. Fingerprints scanned at 214 nm on the basis of CE separation at pH 9.3 were used to characterize seven varieties of yew. The contents of four key taxoids (10-deacetylbaccatin, baccatin III, cephalomannine and paclitaxel) in six Taxus varieties were comparatively determined by HPLC-MS. The set of electropherograms/chromatograms of the various Taxus extracts were subjected to principal component analysis (PCA), using the peak areas of 16 phenolic compounds and 14 taxoids as characteristics. The formation of distinct clusters in accordance with botanical classification proves the suitability of PCA for differentiating varieties of Taxus.

An Approach to the Chemotaxonomic Differentiation of Two European Dog's Mercury Species: Mercurialis annua L. and M. perennis L.

Mercurialis annua and M. perennis are medicinal plants used in complementary medicine. In the present work, analytical methods to allow a chemotaxonomic differentiation of M. annua and M. perennis by means of chemical marker compounds were established. In addition to previously published compounds, the exclusive presence of pyridine-3-carbonitrile and nicotinamide in CH(2) Cl(2) extracts obtained from the herbal parts of M. annua was demonstrated by GC/MS. Notably, pyridine-3-carbonitrile was identified for the first time as a natural product. Further chromatographic separation of the CH(2) Cl(2) extracts via polyamide yielded a MeOH fraction exhibiting a broad spectrum of side-chain saturated n-alkylresorcinols. While the n-alkylresorcinol pattern was similar for both plant species, some specific differences were observed for particular n-alkylresorcinol homologs. Finally, the investigation of H(2) O extracts by LC/MS/MS revealed the presence of depside constituents. Whereas, in M. perennis, a mixture of mercurialis acid (=(2R)-[(E)-caffeoyl]-2-oxoglutarate) and phaselic acid (=(E)-caffeoyl-2-malate) could be detected, in M. annua solely phaselic acid was found. By comparison with synthesized enantiomerically pure (2R)- and (2S)-phaselic acids, the configuration of the depside could be determined as (2S) in M. annua and as (2R) in M. perennis.

Desulfopila inferna sp. nov., a sulfate-reducing bacterium isolated from the subsurface of a tidal sand-flat

A Gram-negative, rod-shaped, sulfate-reducing bacterium (strain JS_SRB250Lac(T)) was isolated from a tidal sand-flat in the German Wadden Sea. 16S rRNA gene sequence analysis showed that strain JS_SRB250Lac(T) belonged to the Desulfobulbaceae (Deltaproteobacteria), with Desulfopila aestuarii MSL86(T) being the closest recognized relative (94.2 % similarity). Higher similarity (96.6 %) was shared with 'Desulfobacterium corrodens' IS4, but this name has not been validly published. The affiliation of strain JS_SRB250Lac(T) to the genus Desulfopila was further supported by analysis of aprBA gene sequences and shared physiological characteristics, in particular the broad range of organic electron donors used for sulfate reduction. Compared with Desulfopila aestuarii MSL86(T), strain JS_SRB250Lac(T) additionally utilized butyrate and succinate and grew chemolithoautotrophically with hydrogen as an electron donor. CO dehydrogenase activity was demonstrated, indicating that the reductive acetyl-CoA pathway (Wood-Ljungdahl pathway) was used for CO(2) fixation. Results of cellular fatty acid analysis allowed chemotaxonomic differentiation of strain JS_SRB250Lac(T) from Desulfopila aestuarii MSL86(T) by the presence of C(17 : 0) cyclo and the absence of hydroxy and unsaturated branched-chain fatty acids. Based on phylogenetic, physiological and chemotaxonomic characteristics, strain JS_SRB250Lac(T) represents a novel species of the genus Desulfopila, for which the name Desulfopila inferna sp. nov. is proposed. The type strain is JS_SRB250Lac(T) (=DSM 19738(T) =NBRC 103921(T)).

Composition and Variability of the Essential Oil in Thymus zygis from Southern Spain

An investigation by GC/MS into the composition and variability of the essential oils contained in 63 individual plants taken from 21 populations of Thymus zygis L. in Southern Spain was carried out. Chemometric investigation of the infraspecific variability of the essential oils of these populations led to the differentiation of seven main chemotypes: thymol, carvacrol, linalool, α-terpinyl acetate, thymol/p-cymene/γ-terpinene, 1,8-cineole/myrcene/spathulenol and 1,8-cineole/α-terpineol. The phenolic compound thymol was the most common constituent in the majority of the samples studied. The concentration of its precursors, p-cymene and γ-terpinene was also noteworthy. There was no chemotaxonomic differentiation between the two subspecies (gracilis and sylvestris) for the Thymus zygis plants studied

Chemotaxonomic significance of distribution and stable carbon isotopic composition of long-chain alkanes and alkan-1-ols in C 4 grass waxes

Grasses (Poaceae) are distributed across the world in broad latitudinal belts and are an important source of C 4 biomass in the geological record of soils as well as lake and marine sediments. We examined long-chain leaf wax components of thirty-five C 4 grasses of the subfamilies Aristidoideae, Chloridoideae and Panicoideae from the southern African grasslands and savannas and three C 3 grasses of the subfamily Pooideae from Peru and Australia and review the relevant botanical, phytogeographic and leaf wax compositional background information. Contents, distribution patterns and molecular stable carbon isotopic compositions of long-chain n-alkanes ( n-C 27 to n-C 35) and n-alkan-1-ols ( n-C 22 to n-C 32) were used to estimate the chemotaxonomic relevance of wax signatures of whole plants, separately for different subfamilies and for members of the three C 4 subtypes (NADP–ME, NAD–ME and PCK). Two grass species were separated into flower heads, leaves and stems and the parts analysed separately. Grass flowers contain remarkable amounts of short-chain n-alkanes, which may have a significant influence on the chemical signature of the whole plant, whereas n-alkanol distribution patterns exhibit no systematics. The stable carbon isotopic composition of both biomarker types in different plant parts is remarkably uniform. Chemotaxonomic differentiation was not possible on a species level based on whole plant samples, but was more successful for averages of subfamily and photosynthetic subtype data. Wax signatures of C 4 grasses are generally distinguishable from those of C 3 species by heavier isotopic values, higher contents of n-C 31 and n-C 33 alkanes and the abundance of the n-C 32 n-alkanol, which is largely absent in C 3 grass waxes. Especially the waxes of the NAD–ME and PCK C 4-subtype grasses, which thrive in extremely arid tropical and subtropical areas, contain high relative amounts of longer-chain n-alkane homologues. The chemical classification on a subfamily level, which is in agreement with previously reported subfamilial phylogeny of grasses, implies an evolutionary wax adaptation of C 4 grasses to warm and arid habitats. Our results confirm the validity of the contents, distribution patterns and molecular stable carbon isotopic compositions of long-chain n-alkanes and alkan-1-ols as indirect proxies of continental climate conditions in environmental studies of the tropics.

Ease of delignification assessment of wood from different Eucalyptus species by pyrolysis (TMAH)-GC/MS and CP/MAS 13C-NMR spectrometry

Flash-pyrolysis in the presence of tetramethylammonium hydroxide (TMAH) of woods from different species of Eucalyptus yields series of guaiacyl-type (G) and syringyl-type (S) units in slightly but characteristically different relative proportions. Such differences have been used to suggest a fine and appropriate index of the ease of delignification of the different Eucalyptus species when pulped by the Kraft process. The pyrolytic data were in agreement with those obtained from CP/MAS 13C-NMR spectra of the woods. On the other hand, the various eucalypt woods showed additional differences in their pyrolytic patterns regarding the relative amounts and structure of the high molecular weight aromatic compounds arising from the pyrolysis of polyphenolic wood constituents, which might be used as a basis for chemotaxonomic differentiation of the origin of the woods

Gas Chromatography/Mass Spectrometry Analysis of the Cuticular Hydrocarbons from Parasitic Wasps of the Genus Muscidifurax

Parasitic Hymenoptera can be difficult to identify by conventional taxonomic techniques. Examination of the cuticular hydrocarbons (CHCs) provides a basis for chemotaxonomic differentiation, which may lead to the discovery of pheromones, and can be a means of examining colonies for species cross-contamination. The parasitic wasps examined were Muscidifurax raptor, M. zaraptor, M. uniraptor, and the gregarious form of M. raptorellus. Species within the genus Muscidifurax, as well as the sex, can clearly be differentiated by examining the gas chromatograms of the CHCs. Identification of the alkanes by mass spectrometry shows uncommon dimethylalkanes and trimethylalkanes for members of the genus. The methyl branched cuticular hydrocarbons of these insects are rare compared to those found on insects reported in the literature, but are present in significant amounts on these insects. Additionally, sexual dimorphism is observed in long chain alkanes (C 21–C 39) present on male and female cuticular surfaces for these species. Females tend to have cuticular hydrocarbons with methyl branches located externally on the carbon backbone chain for dimethyl-, trimethyl-, and tetramethylalkanes, whereas males tend to have dimethyl- and trimethylalkanes located internally on the hydrocarbon backbone chains. Mass spectra of novel and rare methyl branched compounds identified on these parasitoids are presented.