Metabolic characterization of green pods from Vanilla planifolia accessions grown in La Réunion

Large phenotypic variation has been observed between the cultivated vanillas since a single genetic source of Vanilla planifolia was spread to the Indian Ocean and the Indonesia in the 19th century. In order to differentiate the cultivated vanilla plants, genetic studies have been conducted in the past on the plants grown in various regions such as the French island, La Réunion. However, the genetic difference was not big enough to differentiate diverse accessions of V. planifolia. In this study, metabolomics, in which genetic variation could be amplified, was employed to delve into the variation between the cultivated vanilla plants. To obtain a broad view of the metabolome, nuclear magnetic resonance (NMR) spectroscopy was applied to the analysis of V. planifolia green pods. Principal component analysis (PCA) and partial least square-discriminant analysis (PLS-DA) of the data showed that the accessions could be differentiated according to their glucovanillin and glucosides A and B contents. Furthermore, a correlation between the glucovanillin content and the pod length, number of flower and growth capacity of the accessions has been observed from the multivariate data analysis.     

Microtropiosides A–F: ent-Labdane diterpenoid glucosides from the leaves of Microtropis japonica (Celastraceae)

From a 1-BuOH-soluble fraction of a MeOH extract of the leaves of Microtropis japonica, collected in the Okinawa islands, six ent-labdane glucosides, named microtropiosides A–F, were isolated together with one known acyclic sesquiterpene glucoside. Their structures were elucidated by a combination of spectroscopic analyses, and their absolute configurations determined by application of the β-d-glucopyranosylation-induced shift-trend rule in ¹³C NMR spectroscopy and the modified Mosher’s method.     

Two further acylated flavone glucosides from Anisomeles ovata

The structures of two new acylated apigenin glucosides are reported from the aerial parts of Anisomeles ovata. They were separated as their acetates and identified as apigenin 7-O-β-d-(2″,6″-di-O-p-coumaroyl)glucoside and apigenin 7-O-β-d-(4″,6′-di-O-p-coumaroyl)glucoside by ¹H NMR study of the acetates and by chemical degradative methods. The allocation of the p-coumaroyl moieties is also supported by a study of the ¹³C NMR spectrum of the inseparable mixture of glucosides.     

Male-to-female transfer of 5-hydroxytryptophan glucoside during mating in Zygaena filipendulae (Lepidoptera)

Zygaena filipendulae accumulates the cyanogenic glucosides linamarin and lotaustralin by larval sequestration from the food plant or de novo biosynthesis. We have previously demonstrated that the Z. filipendulae male transfers linamarin and lotaustralin to the female in the course of mating. In this study we report the additional transfer of 5-hydroxytryptophan glucoside (5-(β-d-glucopyranosyloxy)-l-Tryptophan) from the Z. filipendulae male internal genitalia to the female spermatophore around 5 h into the mating process. 5-Hydroxytryptophan glucoside is present in the virgin male internal genitalia, and production continues during the early phase of mating. Following initiation of 5-hydroxytryptophan glucoside transfer to the female, the amount in male internal genitalia is drastically reduced until after mating where it is slowly replenished. For unambiguous structural identification, 5-hydroxytryptophan glucoside was chemically synthesized and used as an authentic standard. The biological function of 5-hydroxytryptophan glucoside remains to be established, although we have indications that it may be involved in inducing the female to stay in copula and delay egg-laying to prevent re-mating of the female. To our knowledge 5-hydroxytryptophan glucoside has not previously been reported present in animal tissues.     

The metabolism of [3−3H]oleanolic acid-3-O-mono-[14C]glucoside in isolated cells from Calendula officinalis leaves

The radioactive precursor, [3?³H]oleanolic acid-3-O-mono-[¹⁴C]glucoside was administrated to isolated cells obtained from the leaves of Calendula officinalis. The radioactivity of the precursor was incorporated into fractions containing free oleanolic acid, individual glucosides, glucuronide F and other glucuronides. The ratio of ³H: ¹⁴C radioactivity in these fractions indicated that glucosides were formed in a process involving direct glycosylation of the precursor, whereas the glucuronides were formed from oleanolic acid released by hydrolysis of the precursor. Dynamics curves showed that glucoside II formed by direct glycosylation of the precursor was intensively transformed to other derivatives.     

Structural elucidation and partial synthesis of 3-hydroxyheterodendrin,a cyanogenic glucoside from Acacia sieberiana var. woodii

A new cyanogenic glucoside, isolated from pods of Acacia sieberiana var. woodii, was shown to be (2R)-2- (β-d-glucopyranosyloxy)-3-hydroxy-3-methylbutanenitrile by spectroscopic and chemical methods. The absolute configuration of this glucoside was correlated with that of proacacipetalin by oxymercuration of the latter, followed by borohydride reduction of the product.     

New sweet diterpene glucosides from Stevia rebaudiana

From the leaves of Stevia rebaudiana, two new sweet glucosides, rebaudiosides A and B, were isolated besides the known glucosides, stevioside and steviolbioside. On the basis of IR, MS, ¹H and ¹³C NMR as well as chemical evidences, the structure of rebaudioside B was assigned as 13-O-[β-glucosyl(1-2)-β-glucosyl(1-3)]-β-glucosyl-steviol and rebaudioside A was formulated as its β-glucosyl ester.     

Iridoid glucosides in Griselinia, Aralidium and Toricellia

From three of five investigated species of Griselinia a new iridoid glucoside, griselinoside, was isolated. It was found to be present also in foliage of Aralidium pinnatifidum and Toricellia angulata, accompanied in the former by aralidioside another novel iridoid glucoside. The structures and absolute configurations of the two iridoids were elucidated by NMR spectroscopy and chemical conversions. From G. littoralis and T. angulata the glucosides magnolioside and syringoside respectively were isolated. ¹³C NMR spectra are given for thirteen iridoid derivatives.     

Grevillosides A-F: glucosides of 5-alkylresorcinol derivatives from leaves of Grevillea robusta

From a MeOH extract of leaves of Grevillea robusta, seven compounds (1-7) were isolated. One known compound (7) was identified with a benzyl glucoside, icariside F₂. The structures of the six of these, named grevillosides A-F (1-6), were elucidated on detailed inspection of one- and two-dimensional NMR spectroscopic data as glucosides of 5-alkylresorcinols.     

Biosynthesis of the iridoid glucoside cornin in Verbena officinalis

The biosynthesis of cornin (verbenalin) and dihydrocornin in Verbena officinalis has been investigated. The incorporation of [²H] deoxyloganin was found to be largely independent of the incubation time between one day and a week. An improved method for the preparation of deoxygeniposide from gardenoside is reported and [²H]-iridodial glucoside and [²H]-iridotrial glucoside were prepared from the former. Feeding experiments with young plants using these glucosides, as well as the aglucones, showed much better incorporations for the latter compounds as measured by ²H NMR spectroscopy. ¹³ C-labelled 10-hydroxygeraniol, 10-hydroxycitronellol, iridodial, iridotrial, iridodial glucoside, iridotrial glucoside, deoxyloganic acid, and deoxyloganic acid aglucone were prepared. [¹³C]-Mevalonic acid and the above compounds were fed to plants of medium age, and all gave incorporations measurable by ¹³C NMR spectroscopy into dihydrocornin. The postulated existence of two different metabolic pathways in the biosynthesis of cornin in young and old plants, respectively, could not be established as complete scrambling between the C-3 and C-11 in the iridoid skeleton apparently takes place with all the early precursors. The complete pathway from iridodial forwards to hastatoside has been elucidated.     

Acylated flavonol glucosides of Pinus contorta needles

From fresh Pinus contorta Doug (Coastal) needles four flavonol acylated glucosides and 6-methyl-kaempferol 3-β-D-glucoside were isolated. The three monoacylated glucosides were kaempferol-3-β-D(6-O-p- coumaryl)glucoside, isorhamnetin-3-β-D-(6-O-acetyl)glucoside, quercetin-3-β-D-(p-coumaryl)glucoside and the diacyl compound was kaempferol-3-β-D-(di-p-coumaryl)glucoside.     

Subcellular Localization of 2-(beta-d-Glucosyloxy)-Cinnamic Acids and the Related beta-glucosidase in Leaves of Melilotus alba Desr

The distribution of the glucosides of trans- and cis-2-hydroxy cinnamic acid and of the β-glucosidase which hydrolyzes the latter glucoside was examined in preparations of epidermal and mesophyll tissue obtained from leaves of sweet clover (Melilotus alba Desr.). The concentrations of glucosides in the two tissues were about equal when compared on the basis of fresh or dry weight. Inasmuch as the epidermal layers account for no more than 10% of the leaf volume, the mesophyll tissue contains 90% or more of the glucosides. Vacuoles isolated from mesophyll protoplasts contained all of the glucosides present initially in the protoplasts.     

5,7-Bisdeoxycynanchoside,an iridoid glucoside from Macfadyena cynanchoides

A new iridoid glucoside from Macfadyena cynanchoides leaves has been identified by spectral (¹H and ¹³C NMR) and chemical procedures as 5,7     

Diversification of an ancient theme: hydroxynitrile glucosides

Many plants produce cyanogenic glucosides as part of their chemical defense. They are alpha-hydroxynitrile glucosides, which release toxic hydrogen cyanide (HCN) upon cleavage by endogenous plant beta-glucosidases. In addition to cyanogenic glucosides, several plant species produce beta- and gamma-hydroxynitrile glucosides. These do not release HCN upon hydrolysis by beta-glucosidases and little is known about their biosynthesis and biological significance. We have isolated three beta-hydroxynitrile glucosides, namely (2Z)-2-(beta-D-glucopyranosyloxy)but-2-enenitrile and (2R,3R)- and (2R,3S)-2-methyl-3-(beta-D-glucopyranosyloxy)butanenitrile, from leaves of Ribesuva-crispa. These compounds have not been identified previously. We show that in several species of the genera Ribes, Rhodiola and Lotus, these beta-hydroxynitrile glucosides co-occur with the L-isoleucine-derived hydroxynitrile glucosides, lotaustralin (alpha-hydroxynitrile glucoside), rhodiocyanosides A (gamma-hydroxynitrile glucoside) and D (beta-hydroxynitrile glucoside) and in some cases with sarmentosin (a hydroxylated rhodiocyanoside A). Radiolabelling experiments demonstrated that the hydroxynitrile glucosides in R. uva-crispa and Hordeum vulgare are derived from L-isoleucine and L-leucine, respectively. Metabolite profiling of the natural variation in the content of cyanogenic glucosides and beta- and gamma-hydroxynitrile glucosides in wild accessions of Lotus japonicus in combination with genetic crosses and analyses of the metabolite profile of the F2 population provided evidence that a single recessive genetic trait is most likely responsible for the presence or absence of beta- and gamma-hydroxynitrile glucosides in L. japonicus. Our findings strongly support the notion that the beta- and gamma-hydroxynitrile glucosides are produced by diversification of the cyanogenic glucoside biosynthetic pathway at the level of the nitrile intermediate.     

Two secoiridoid glucosides from Jasminum mesnyi

Besides the known glucoside jasminin and an unidentified glucoside, two new secoiridoid glucosides,jasmoside and jasmesoside have been isolated from the leaves of Jasminum mesnyi and their structures elucidated.     

Furanocoumarins from Dorsteniafoetida

The linear furanocoumarins 5-(2,3-epoxy-3-methyl-butoxy)-chalepensin, 5-methoxy-3-(3-methyl-2,3-dihydroxybutyl)-psoralen-diacetate (7), 5-methoxy-3-[3-(β-d-glucopyranosyloxy)-2-acetyloxy-3-methyl-butyl]-psoralen and 5-(3-methyl-2,3-dihydroxybutyloxy)-3-[3-(β-d-glucopyranosyloxy)-2-hydroxy-3-methyl-butyl]-psoralen, and the coumarin derivative 7-hydroxy-5-methoxy-6-carboxymethyl-3-[3-(β-d-glucopyranosyloxy)-2-hydroxy-3-methyl-butyl]-coumarin were isolated from the leaves of Dorstenia foetida (Moraceae) along with the known compounds psoralen, bergapten, isopimpinellin, phellopterin, 5-methoxychalepensin and turbinatocoumarin. Further furanocoumarins were characterized by ESI-MS/MS investigations. The nonpolar extracts of D. foetida exhibit antifungal, antibacterial and cytotoxic activity, however, no anthelminthic activity.     

Form and level of coumarin in deer’s tongue,Trilisa odoratissima

Fresh leaves of deer’s tongue contain large quantities (more than 10% of the dry weight, in some cases) of o-hydroxycinnamic acid (o-HCA). Bothcis- andtrans-o- HCA are present, and both isomers exist in the fresh tissue predominantly as glucosides. Cured deer’s tongue leaves contain relatively high levels of coumarin and lower amounts of o-HCA glucosides. It is probable that during the curing processcis-o-HCA glucoside is hydrolyzed by an endogenous ß-glucosidase, and that the liberated cis-o-HCA lactonizes spontaneously to form coumarin.     

Cyanogenic glycosides and menisdaurin from Guazuma ulmifolia, Ostrya virgininana, Tiquilia plicata and Tiquilia canescens

The major cyanogenic glycoside of Guazuma ulmifolia (Sterculiaceae) is (2R)-taxiphyllin (>90%), which co-occurs with (2S)-dhurrin. Few individuals of this species, but occasional other members of the family, have been reported to be cyanogenic. To date, cyanogenic compounds have not been characterized from the Sterculiaceae. The cyanogenic glycosides of Ostrya virginiana (Betulaceae) are (2S)-dhurrin and (2R)-taxiphyllin in an approximate 2:1 ratio. This marks the first report of the identification of cyanogenic compounds from the Betulaceae. Based on NMR spectroscopic and TLC data, the major cyanogenic glucoside of Tiquilia plicata is dhurrin, whereas the major cyanide-releasing compound of Tiquilia canescens is the nitrile glucoside, menisdaurin. NMR and TLC data indicate that both compounds are present in each of these species. The spectrum was examined by CI-MS, ¹H and ¹³C NMR, COSY, 1D selective TOCSY, NOESY, and ¹J/^2,3J HETCOR experiments; all carbons and protons are assigned. The probable absolute configuration of (2R)-dhurrin is established by an X-ray crystal structure. The ¹H NMR spectrum of menisdaurin is more complex than might be anticipated, containing a planar conjugated system in which most elements are coupled to several other atoms in the molecule. The coupling of one vinyl proton to the protons on the opposite side of the ring involves a ⁶J- and a ^5/7J-coupling pathway. A biogenetic pathway for the origin of nitrile glucosides is proposed.     

Structure of renifolin and reconfirmation of the structure of pirolatin

The ¹H and ¹³C NMR spectral analysis of the glucoside renifolin, isolated from Pyrola renifolia, demonstrated the so far unknown binding site of the glucose moiety to be at C-8 and hence its structure as 8-β-D-glucosyloxy-2,7-dimethyl-1,4-dihydronaphthalen-5-ol. The earlier reported structure for the glucoside pirolatin, isolated from Pyrola japonica, was also reconfirmed by the ¹³C NMR spectral analysis.     

Effect of benzothiadiazole on the metabolome of Arabidopsis thaliana

Benzothiadiazole (BTH) is a functional analog of the plant endogenous hormone-like compound, salicylic acid (SA), which is required for the induction of plant defense genes leading to systemic acquired resistance (SAR). Previous molecular and genetic studies have suggested that BTH itself might potentiate SAR resulting in the induction of several pathogenesis-related (PR) genes. However, the changes in the metabolome, which occur as a result of BTH-treatment, remain unclear. In this study, metabolic alterations in BTH-treated Arabidopsis thaliana were investigated using nuclear magnetic resonance (NMR) spectroscopy followed by multivariate data analyses such as principal component analysis (PCA) and partial least square-discriminant analysis (PLS-DA). Both PCA and PLS-DA show that increase of glucose, glutamine, inositol, malic acid, sucrose, and threonine as well as BTH and its degraded metabolites contribute to the clear discrimination of the metabolome of BTH-treated Arabidopsis from control plants. However, the levels of phenolic metabolites, which have generally been observed to be induced by other signaling molecules were significantly reduced in BTH-treated Arabidopsis. In addition to these changes due to BTH-treatment, it was also found that the EtOH used as a solvent in this treatment may per se act as an inducer of the accumulation of a flavonoid.