Four iridoids from Randia canthioides

Four new iridoids, 10-dehydrogardenoside, dimeric 10-dehydrogardenoside, randioside and deacetylasperulosidic acid methyl ester aglycone, have been isolated together with three known iridoid glucosides, gardenoside, deacetylasperulosidic acid methyl ester and scandoside methyl ester, from Randia canthioides. It is conceivable that dimeric 10-dehydrogardenoside could be an artefact formed during the isolation process.     

Iridoid glucosides from Randia spinosa (Rubiaceae)

An iridoid glucoside: randinoside, along with five known iridoids: galioside, deacetylasperulosidic acid methyl ester, scandoside methyl ester, geniposide and gardenoside, were isolated from the stems of Randia spinosa. The structures were determined by spectroscopic analysis, including 2D NMR techniques.     

Iridoid glucosides with insecticidal activity from Galium melanantherum

The insecticidal activity of the endemic species Galium melanantherum was evaluated against Crematogaster scutellaris ants and Kalotermes flavicollis termites. Iridoid glucosides 1-7 were isolated for the first time as metabolites of the investigated plant, along with the coumarin scopolin. The main components of the extract were found to be the non-acetylated iridoids: geniposidic acid (1), 10-hydroxyloganin (2), deacetyldaphylloside (3), monotropein (4), deacetylasperulosidic acid (5) and scandoside (6), while asperulosidic acid (7) was present only in minute quantities. All isolated metabolites were identified on the basis of their spectral data. Laboratory bioassays revealed significant levels of toxicity for 1-4 against Kalotermes flavicollis termites and Crematogaster scutellaris ants.     

Iridoid glycosides of Cornus canadensis: a comparison with some other Cornus species

The iridoid glycosides scandoside, scandoside methyl ester, monotropein, and galioside were found in Cornus canadensis from several widely distributed collection sites. Cornin and hastatoside were isolated from C. nuttallii. No iridoids were found in C. stolonifera, that instead yielded cornoside and halleridone, also independent of collection location. The results were compared with previous studies and current phylogenetic work on the genus Cornus.     

Iridoid glucosides in Plantago alpina and P. Altissima

Two species of Plantago, namely P. Alpina and P. altissima were investigated. From the former, nine iridoid glucosides and verbascoside were isolated. Together with the known iridoids gardoside, geniposidic acid, 8-epi-loganic acid, mussaenosidic acid, aucubin, monomelittoside and melittoside, two new glucosides were found: 10-O-acetylgeniposidic acid and alpinoside, another compound with a 10-O-acetyl group. From P. altissima verbascoside and isoverbascoside were isolated together with the known iridoids gardoside, 8-epi-loganic acid, catalpol, aucubin, and hookerioside as well as the new compound desacetylhookerioside.     

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.     

Iridoids,flavonoids, and monoterpene diglycoside from the roots of Triosteum himalayanum Wall.

The phytochemical investigation of the roots of Triosteum himalayanum Wall. led to the isolation of eleven iridoids (1–6 and 8–12), one monoterpene diglycoside (7), and four flavonoids (13–16), of which 4′,6′-di-O-isopropylidene sweroside (1) and secologanin diethylacetal (2) were new iridoid glucosides. The existence of iridoids and flavonoids provided further confirmation of the typical profile of the secondary metabolites found in the genus Triosteum, suggesting a close relationship among the species of Caprifoliaceae.     

Iridoids,iridoid-triterpenoid congeners and lignans from Desfontainia spinosa

The leaves of Desfontainia spinosa; were found to contain the three known seco-iridoids secoxyloganin, dimethyl secologanoside and sweroside in addition to the three iridoids loganin, loganetin and loganic acid previously reported. In addition a novel loganin derivative 7-O-(p-coumaroyl)-loganin was isolated. The leaves were also found to contain a novel type of compound consisting of ester-linked triterpene and seco-iridoid congeners between 24-hydroxytormentic acid and secoxyloganin. These were named desfontainic acid, a monoglucoside, and desfontainoside, the corresponding diglucoside. Desfontainoside only could be detected in the stems. The stem contained the same iridoids and also the known furofuran lignans (+)-syringaresinol, (+)-syringaresinol O-β-D-glucopyranoside and liriodendrin. The iridoids present provide chemotaxonomic evidence for retaining Desfontainia in the Loganiaceae as a separate tribe the Desfontaineae. None of the compounds present forms a basis for the reputed hallucinogenic activity.     

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.     

Two new iridoid glucosides from Gardenia jasminoides fruits

From the fruits of Gardenia jasminoides which have been employed as Chinese crude drug “Shan-zhii”, two further new iridoid glucosides, gardoside (8,10-dehydrologanic acid) and scandoside methyl ester have been isolated and their structures have been established.     

Iridoid glucosides from Utricularia australis and Pinguicula vulgaris (lentibulariaceae)

Utricularia australis contained 6-deoxycatalpol, a new iridoid glucoside, besides aucubin, gardoside and mussaenosidic acid. From Pinguicula vulgaris was isolated catalpol, globularin and 10-(Z)-cinnamoyl-catalpol, the latter being a new compound. Thus, the iridoids found in Lentibulariaceae belong to structural types which are common in Scrophulariaceae and related families.     

Evaluation of human neutrophil elastase inhibitory effect of iridoid glycosides from Hedyotis diffusa

Five iridoid glycosides were isolated from the MeOH extract of Hedyotis diffusa, and their structures were elucidated as E-6-O-p-methoxycinnamoyl scandoside methyl ester (1), Z-6-O-p-methoxycinnamoyl scandoside methyl ester (2), E-6-O-p-feruloyl scandoside methyl ester (3), E-6-O-p-coumaroyl scandoside methyl ester (4), and Z-6-O-p-coumaroyl scandoside methyl ester (5) by interpretation of their spectroscopic data. All the isolated compounds were evaluated for human neutrophil elastase inhibitory effect, and compound 1 showed potent activity with an IC₅₀ value of 18.0 μM. The molecular docking simulation suggested a structural model for the inhibition of human neutrophil elastase by compound 1.     

Iridoid glucosides as taxonomic markers in the genera Lantana,Lippia, Aloysia and Phyla

Nine species of Lantana, Lippia, Aloysia and Phyla have been examined for iridoids. Six of the species contain iridoid glucosides including pulchelloside I, mussaenoside, lamiide, durantoside I, geniposide and theviridoside as well as the sodium salts of geniposidic acid and theveside. A quinol glucoside, cornoside, has been isolated from Phyla nodiflora. The distribution of iridoids and cornoside shows a good correlation with the classification proposed by El-Gazzar and Watson.     

Iridoid glucosides in Avicennia marina

2′-Cinnamoyl-mussaenoside, 10-O-(5-phenyl-2,4-pentadienoyl)-geniposide, 7-O-(5-phenyl-2,4-pentadienoyl)-8-epiloganin, and the known iridoids geniposide and mussaenoside have been isolated from a methylated extract of the leaves of Avicennia marina. Evidence is presented that the iridoids occur as the free acids in the plant. The taxonomic significance of these findings is discussed.     

Iridoids from the roots of Triosteum pinnatifidum

A chemical investigation of the roots of Triosteum pinnatifidum led to the isolation of 10 iridoids, elucidated as triohimas A–C, naucledal, secologanin dimethyl acetal, grandifloroside, sweroside, loganin, vogeloside and (E)-aldosecologanin. Most of the compounds were derived from loganin or secologanin with a glucose moiety at C-1 position. The results indicate a close relationship between the two genera Triosteum and Lonicera, and support the viewpoint that the iridoids derived from loganin or secologanin could be the chemotaxonomic markers of the Caprifoliaceae family.     

Chemotaxonomic interest of iridoids isolated from a Malagasy species: Perichlaena richardii

Three known iridoid glycosides, verminoside (1), 6-O-trans-caffeoyl-ajugol (2), and 10-O-trans-caffeoyl-catalpol (3), together with 1-β-O-caffeoyl-d-glucose (4), caffeic acid (5), and a flavonol glycoside, rutin (6), were isolated from the leaves of Perichlaena richardii Baill. (Bignoniaceae), an endemic species to Madagascar. This is the first report of these compounds from this species. The structures of the isolated compounds were established using different spectroscopic methods including extensive 1D and 2D-NMR and mass spectrometry. The activity of verminoside, rutin and caffeic acid on enzymes involved in inflammation, cyclooxygenases and lipoxygenases, was determined on human peripheral venous blood samples. Moreover, the distribution of iridoids among the clades of Bignoniaceae, according to Von Poser et al. in 2000, was revisited on the basis of the new classification of Bignoniaceae described in 2009 by Olmstead et al. The chemotaxonomy of iridoids isolated from P. richardii, in addition to the Bignoniaceae family as a whole, is also discussed.     

Iridoid glucosides in Avicennia officinalis

The new iridoids avicennioside and 7-cinnamoyl-8-epiloganic acid, as well as the known compounds geniposidic acid and 2′-cinnamoyl-mussaenosidic acid, have been isolated from the leaves of Avicennia officinalis. In the plant the acids are accumulated as salts. The taxonomic significance of these findings is discussed.     

HPLC analysis of the seasonal and diurnal variation of iridoids in cultivars of Antirrhinum majus

In this paper we show the seasonal and diurnal variation in the content of the four iridoids found in cultivars of Antirrhinum majus, antirrhinoside, antirrhide, 5-glucosyl-antirrhinoside and linarioside. The seasonal variation in total iridoid content showed a marked bimodal distribution with high total values (around 100 mg/g dry matter) early and late in the season and a very low content of all iridoids coinciding with the onset of flowering at the beginning of August. The relative contribution of antirrhinoside was significantly higher before flowering than after bud break. The relative decrease in antirrhinoside was counteracted by an increase of antirrhide, which was significantly higher after the onset of flowering than before. This pattern indicates a change in biosynthesis, although no explanation can be given to the phenomenon. The diurnal variation showed a variation between 20 and 60 mg/g dry weight, but there was no relation to light/darkness conditions, temperature patterns or water content. The analyses were performed by HPLC. The applied method has not previously been used in the quantification of iridoids, but was developed specifically for the analyses of cultivars of Antirrhinum majus. We have fully validated the method during its development. The limit of detection was calculated to 0.004 mg/ml and the limit of quantification was 0.01 mg/ml.     

A secoiridoid glucoside of Jasminum humile var. revolutum

The structure of jasminoside, a new secoiridoid glucoside isolated from Jasminum humile var. revolutum. was elucidated to be 10-cinnamoyloxyoleoside 7-methyl ester.     

Iridoids of garrya elliptica as plant growth inhibitors

Extracts from catkins of Garrya elliptica inhibit the growth of wheat embryos. The components responsible for this activity have been identified as the iridoids geniposide and geniposidic acid together with their aglucones.