Amritosides A, B, C and D: clerodane furano diterpene glucosides from Tinospora cordifolia

Four new clerodane furano diterpene glucosides (amritosides A, B, C and D) were isolated as their acetates from Tinospora cordifolia stems. The structures of these compounds were established on the basis of spectroscopic studies.     

Chemotaxonomic markers in Digitalideae (Plantaginaceae)

In a chemosystematic investigation of Digitalideae (Plantaginaceae), the water-soluble part of extracts of two species of Digitalis, two species of Isoplexis, as well as Erinus alpinus and Lafuentea rotundifolia were studied with regard to their content of main carbohydrates, iridoids and caffeoyl phenylethanoid glycosides (CPGs). Digitalis and Isoplexis contained sorbitol, cornoside and a number of other phenylethanoid glycosides including the new tyrosol beta-D-mannopyranoside, sceptroside but were found to lack iridoid glucosides. Erinus contained mainly glucose, the new 8,9-double bond iridoid, erinoside, and a number of known iridoid glucosides including two esters of 6-rhamnopyranosylcatalpol, as well as the CPG poliumoside. Finally, Lafuentea was characterized by the presence of glucose, aucubin and cryptamygin B but apparently lacked CPGs. The chemosystematic significance of the isolated compounds is discussed.     

Cyanogenic glucosides in the biological warfare between plants and insects: the Burnet moth-Birdsfoot trefoil model system

Cyanogenic glucosides are important components of plant defense against generalist herbivores due to their bitter taste and the release of toxic hydrogen cyanide upon tissue disruption. Some specialized herbivores, especially insects, preferentially feed on cyanogenic plants. Such herbivores have acquired the ability to metabolize cyanogenic glucosides or to sequester them for use in their own predator defense. Burnet moths (Zygaena) sequester the cyanogenic glucosides linamarin and lotaustralin from their food plants (Fabaceae) and, in parallel, are able to carry out de novo synthesis of the very same compounds. The ratio and content of cyanogenic glucosides is tightly regulated in the different stages of the Zygaena filipendulae lifecycle and the compounds play several important roles in addition to defense. The transfer of a nuptial gift of cyanogenic glucosides during mating of Zygaena has been demonstrated as well as the possible involvement of hydrogen cyanide in male assessment and nitrogen metabolism. As the capacity to de novo synthesize cyanogenic glucosides was developed independently in plants and insects, the great similarities of the pathways between the two kingdoms indicate that cyanogenic glucosides are produced according to a universal route providing recruitment of the enzymes required. Pyrosequencing of Z. filipendulae larvae de novo synthesizing cyanogenic glucosides served to provide a set of good candidate genes, and demonstrated that the genes encoding the pathway in plants and Z. filipendulae are not closely related phylogenetically. Identification of insect genes involved in the biosynthesis and turn-over of cyanogenic glucosides will provide new insights into biological warfare as a determinant of co-evolution between plants and insects.     

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.     

Cyanogenesis in plants and arthropods

Cyanogenic glucosides are phytoanticipins known to be present in more than 2500 plant species. They are regarded as having an important role in plant defense against herbivores due to bitter taste and release of toxic hydrogen cyanide upon tissue disruption, but recent investigations demonstrate additional roles as storage compounds of reduced nitrogen and sugar that may be mobilized when demanded for use in primary metabolism. Some specialized herbivores, especially insects, preferentially feed on cyanogenic plants. Such herbivores have acquired the ability to metabolize cyanogenic glucosides or to sequester them for use in their own defense against predators. A few species of arthropods (within diplopods, chilopods and insects) are able to de novo biosynthesize cyanogenic glucosides and some are able to sequester cyanogenic glucosides from their food plant as well. This applies to larvae of Zygaena (Zygaenidae). The ratio and content of cyanogenic glucosides is tightly regulated in Zygaena filipendulae, and these compounds play several important roles in addition to defense in the life cycle of Zygaena. The transfer of a nuptial gift of cyanogenic glucosides during mating of Zygaena has been demonstrated as well as the involvement of hydrogen cyanide in male attraction and nitrogen metabolism. As more plant and arthropod species are examined, it is likely that cyanogenic glucosides are found to be more widespread than formerly thought and that cyanogenic glucosides are intricately involved in many key processes in the life cycle of plants and arthropods.     

Flavone C-glycosides from Lupinus hartwegii

From the aerial parts of Lupinus hartwegii, two new flavone C-glycosides apigenin-7-O-beta-apiofuranosyl-6, 8-di-C-beta-glucopyranoside (1) and apigenin-7-O-beta-apiofuranosyl-6-C-beta-glucopyranosyl-8-C-(6z.qprime;-O-E-feruloyl)- beta-glucopyranoside (2) have been isolated together with two known isoflavonoid glucosides genistein-7-O-beta-glucopyranoside (3) and genistein-7, 4'-di-O-beta-glucopyranoside (4) as well as two known compounds ferulic acid 4-O-beta-glucopyranoside (5) and sparteine (6). The structures of the isolated compounds were verified by means of MS and NMR spectral analyses.     

Coumarin glucosides from Cruciata taurica

Two new coumarin glycosides (1 and 2) along with two known coumarin glucosides, daphnin (3) and daphnetin glucoside (4) were isolated from the aerial parts of Cruciata taurica. The structures of the new compounds were elucidated by spectral methods and chemical means as 7-O-(6' -acetoxy-beta-D-glucopyranosyl)-8-hydroxycoumarin (1) and 7-O-[6 '-O-(3',4'-dihydroxycinnamoyl)-beta-D-glucopyranosyl]-8-hydroxycoumarin (2). The phylogenetic significance of coumarins in C. taurica was discussed.     

Iridoid glucosides of Paederota lutea and the relationships between Paederota and Veronica

In a chemical investigation of the water soluble compounds in Paederota lutea eight known iridoids were isolated together with a new one with a 8,9-double bond, namely paederotoside (10-O-benzoyl-6'-O-alpha-arabino(1-->6)-beta-glucopyranosyl arborescosidic acid) and the 6-hydroxy-flavone glucoside 4'-O-methylscutellarein 7-O-beta-glucopyranoside. The known iridoid glucosides were 8-epiloganic acid, gardoside, aucubin, catalpol and the 6-O-esters of catalpol: veronicoside, catalposide, amphicoside and verproside. The compounds isolated show that Paederota has a glycoside content almost identical to that of a general Veronica species, and this is in good agreement with the results from recent investigations of the phylogeny of Veronica and its closest relatives, where Paederota is placed as a sister-group next to Veronica. In an analysis of the iridoid glucosides from some of these relatives, it is shown that Veronica, Paederota, Picrorhiza and Veronicastrum are all characterized by containing 6-O-esters of catalpol. Some less closely related taxa namely: Lagotis, Wulfenia, Plantago, Aragoa and Globularia instead contain 10-O-esters of catalpol or aucubin.     

Glucosides from the roots of Capparis tenera

Two new lignan glucosides, compounds 2 and 3, two new 1H-indole-alkaloid glucosides, 5 and 6, as well as two new phenolic glucosides, 7 and 10, were isolated from the roots of Capparis tenera, together with five known compounds. Their structures were characterized by chemical and spectroscopic methods. Most of these isolates were obtained for the first time from Capparidaceae. The antioxidant and anti-inflammatory activities of the new compounds were investigated.     

Prenylated xanthone glucosides from Ural's lichen Umbilicaria proboscidea

Two new compounds isolated from an extract of a Central Asian lichen [Umbilicaria proboscidea (L.) Schrader=Syn.: Gyrophora proboscidea (L.) Ach.] are glucosides with mono- and di-prenylated xanthones as the aglycones and a saccharide moiety from two glucoses linked at C-7. The structures were elucidated on the basis of extensive spectroscopic analysis (1D and 2D NMR, MS, IR and UV) and by hydrolysis.     

Phytotoxic cis-cinnamoyl glucosides from Spiraea thunbergii

Spiraea thunbergii Sieb. was found to contain 1-O-cis-cinnamoyl-beta-D-glucopyranose and 6-O-(4'-hydroxy-2'-methylene-butyroyl)-1-O-cis-cinnamoyl-beta-D-glucopyranose as major plant growth inhibitory constituents along with related compounds of lower phytotoxicity including 6-O-(trans-cinnamoyl)-1-O-(4"-hydroxy-3"-methyl-furan-2"-one)-beta-D-glucopyranose, 6-O-(4'-hydroxy-2'-methylene-butyroyl)-1-O-trans-cinnamoyl-beta-D-glucopyranose, and 1-O-trans-cinnamoyl-beta-D-glucopyranose. The former three compounds were cinnamoyl glucosides.     

Chromone and chromanone glucosides from Hypericumsikokumontanum and their anti-Helicobacter pylori activities

Chromone glucosides, takanechromones A-C (1, 2 and 5) and chromanone glucosides, named takanechromanones A and B (3 and 4), were isolated from the methanolic extracts of Hypericumsikokumontanum together with 27 known compounds. Their structures were established based on spectroscopic evidence. The isolated compounds and some chromone derivatives were assayed for antimicrobial activity against Helicobacter pylori and cytotoxicity against human cancer cell lines.     

Euodionosides A-G: megastigmane glucosides from leaves of Euodia meliaefolia

From a 1-BuOH-soluble fraction of the MeOH extract of leaves of Euodia meliaefolia, collected in Okinawa, seven megastigmane glucosides, named euodionosides A-G, were isolated together with three known megastgmane glucosides, and two aliphatic and three phenolic compounds. Their structures were elucidated through a combination of spectroscopic analyses and application of the modified Mosher's method.     

Aromatic compound glucosides,alkyl glucoside and glucide from the fruit of anise

From the polar portion of the methanolic extract of the fruit of anise (Pimpinella anisum L.), which has been used as a spice and medicine since antiquity, four aromatic compound glucosides, an alkyl glucoside and a glucide were isolated together with 24 known compounds. The structures of the new compounds were clarified as (E)-3-hydroxyanethole beta-D-glucopyranoside, (E)-1'-(2-hydroxy-5-methoxyphenyl)propane beta-D-glucopyranoside, 3-hydroxyestragole beta-D-glucopyranoside, methyl syringate 4-O-beta-D-glucopyranoside, hexane-1,5-diol 1-O-beta-D-glucopyranoside and 1-deoxy-L-erythritol 3-O-beta-D-glucopyranoside by spectral investigation.     

Differentiation-dependent levels of benzofuran-type resveratrol dimers in root cultures of Anigozanthos preissii

The level of secondary compounds formed by sterile root cultures of Anigozanthos preissii depends on the differentiation state. Cultures showing shoot formation and accelerated growth are depleted in stilbenes, stilbene glucosides, and phenylphenalenones. Three glucosides of anigopreissin A, a benzofuran-type resveratrol dimer, were isolated from slow-growing cultures and their structures elucidated by spectrometric methods.     

Acylated flavone glycosides from Veronica

A survey of the flavonoid glycosides of selected taxa in the genus Veronica yielded two new acylated 5,6,7,3',4'-pentahydroxyflavone (6-hydroxyluteolin) glycosides and two unusual allose-containing acylated 5,7,8,4'-tetrahydroxyflavone (isoscutellarein) glycosides. The new compounds were isolated from V. liwanensis and V. longifolia and identified using NMR spectroscopy as 6-hydroxyluteolin 4'-methyl ether 7-O-alpha-rhamnopyranosyl(1"'-->2")[6"-O-acetyl-beta-glucopyranoside] and 6-hydroxyluteolin 7-O-(6"-O-(E)-caffeoyl)-beta-glucopyranoside, respectively. Isoscutellarein 7-O-(6"'-O-acetyl)-beta-allopyranosyl(1"'-->2")-beta-glucopyranoside was obtained from both V. intercedens and V. orientalis and its 4'-methyl ether from V. orientalis only. Complete 1H and 13C NMR spectral assignments are presented for both isoscutellarein glycosides. Two iridoid glucosides new to the genus Veronica (melittoside and globularifolin) were also isolated from V. intercedens.     

Galloyl, caffeoyl and hexahydroxydiphenoyl esters of dihydrochalcone glucosides from Balanophora tobiracola

Seven galloyl, caffeoyl and (S)-hexahydroxydiphenoyl (HHDP) esters of dihydrochalcone glucosides were isolated from Balanophora tobiracola; based on spectroscopic and chemical evidence, their structures were determined to be 6'-O-galloyl-, 3',4'-di-O-galloyl-, 4',6'-di-O-galloyl-, 4',6'-O-(S)-HHDP-, 3'-O-galloyl-4',6'-O-(S)-HHDP-, 3'-O-caffeoyl-4',6'-O-(S)-HHDP-3-hydroxyphloretin 4'-O-beta-D-glucosides and 3'-O-galloyl-4',6'-O-(S)-HHDP-phloretin 4'-O-beta-D-glucoside, respectively. By contrast, these compounds were not found in the taxonomically related B. japonica. The 3'-galloyl-4',6'-HHDP esters of the dihydrochalcone glucosides showed strong inhibitory activities against alpha-glucosidase. Four known compounds were also isolated namely, (+/-)-eriodictyol 7-O-beta-D-glucoside, 1-O-caffeoyl-3-O-galloyl-beta-D-glucose, phloretin 4'-O-beta-D-glucoside, and 3-hydroxyphloretin 4'-O-beta-D-glucoside.     

A new phenylethanoid triglycoside in Veronica beccabunga L

Besides the expected iridoid glucosides aucubin and catalpol as well as three known esters of the latter, Veronica beccabunga (brooklime) was shown to contain five carboxylated iridoid glucosides, namely gardoside, mussaenosidic acid, 8-epiloganic acid, arborescosidic acid and alpinoside. In addition to these compounds, the plant contained salidroside and a previously unknown caffeoyl phenylethanoid glycoside (CPG) which we have named chionoside J. The structure was elucidated mainly by 1D and 2D NMR spectroscopy to be 2″-(β-glucopyranosyl)-plantamajoside. The distribution of plantamajoside and its derivatives as well as that of carbocyclic iridoids with an 8,9-double bond is briefly discussed, and it is noted that such compounds are mainly confined to the tribe Veroniceae of the Plantaginaceae.     

Maltol glucosides from the tuber of Smilax bockii

Two maltol glucosides, bockiosides A and B, along with 10 known compounds, were isolated from the tuber of Smilax bockii (Liliaceae), and their structures were elucidated by spectral experiments, chemical analysis and comparison with literature data.     

Phenolic glucosides from Hasseltia floribunda

The leaves of Hasseltia floribunda were examined for their chemical constituents. Twelve phenolic glucosides, namely three hydroxycyclohexenyl acyl glucosides, four acylated salicortin derivatives, and five coumaroyl salicin derivatives, were isolated along with eight known phenolic glycosides, six known flavones, and two known sesquiterpenoid cyclohexenone derivatives. The structures of the isolated compounds were elucidated by NMR spectroscopic and HRMS spectrometric methods and by comparing analytical data with those of related structures.