Acylated iridoid glycosides and acylated rhamnopyranoses from Gmelina arborea flowers

Nine acylated iridoid glycosides (1–9), five acylated rhamnopyranoses (10–14) and verbascoside (15) were isolated from Gmelina arborea flowers, including 5 new compounds (1, 2, and 10–12). The cytoprotective activity of 11 selected compounds (1–8, 10, 11, and 15) against CCl₄-induced cytotoxicity on liver was determined. Compounds 1, 2, 4, 7, 8 and 15 displayed hepatoprotective activity. 6-O-α-l-(2″, 3″-di-O-trans-p-hydroxycinnamoyl)rhamnopyranosylcatalpol (2) exhibited the most potent cytoprotective effect with an EC₅₀ value of 42.5 μM (SI = 19.3) compared with biphenyldimethylesterate (DDB, EC₅₀ = 277.3 μM, SI = 9.8) and bicylo-ethanol (EC₅₀ = 279.2 μM, SI = 12.2). Among the acylated iridoid glycosides, the compounds (2 and 8) containing phenolic hydroxy groups were more active than were those lacking them.     

Iridoid glycosides from the stems of Pithecoctenium crucigerum (Bignoniaceae)

Sixteen crude extracts from six Panamanian plants of the family Bignoniaceae were submitted to rapid TLC tests against DPPH and acetylcholinesterase. Pithecoctenium crucigerum (L.) A.H. Gentry, which showed interesting activity against DPPH, has been studied. The chemical investigation of the methanol extract from the stems afforded the iridoid glycoside theviridoside and three derivatives (6'-O-cyclopropanoyltheviridoside, 10-O-hydroxybenzoyltheviridoside and 10-O-vanilloyltheviridoside), along with five known phenylethanoid glycosides (verbascoside, isoverbascoside, forsythoside B, jionoside D and leucosceptoside B). These last compounds were all active against DPPH. The structures were determined by means of spectrometric and chemical methods, including 1D and 2D NMR experiments and MS analysis.     

Iridoid and phenolic glycosides from Morinda coreia

From the leaves and branches of Morinda coreia, six compounds [yopaaosides A-C, 10-O-acetylmonotropein, 6-O-acetylscandoside and 3,4,5-trimethoxyphenyl 1-O-beta-apiofuranosyl (1"-->6')-beta-glucopyranoside] have been isolated together with five known compounds. Structural elucidations were based on analyses of physical and spectroscopic data.     

Iridoid glycosides from Harpagophytum procumbens D.C. (devil's claw)

Iridoid glycosides, harprocumbide A (6'-O-alpha-D-galactopyranosylharpagoside, 1) and harprocumbide B (6'-O-(cis-p-coumaroyl)-procumbide, 2) were isolated from the tubers of Harpagophytum prucumbens D.C., along with nine known iridoid glycosides 6-O-alpha-D-galactopyranosylharpagoside (3), and harpagoside (4), harpagide (5), 8-cinnamoylmyoporoside (6), 8-O-feruloylhapagide (7), procumbide (8), 6'-O-(p-coumaroyl)-procumbide (9), 8-O-(p-coumaroyl)-harpagide (10) and 8-O-(cis-p-coumaroyl)-harpagide (11). Compound 10 showed marginal inhibition activity against macrophages respiratory burst.     

Iridoid glycosides and cucurbitacin glycoside from Neopicrorhiza scrophulariiflora

Three iridoid glycosides, picrorosides A (1), B (2) and C (3), and a cucurbitacin glycoside, scrophoside A (4), were isolated from the rhizomes of Neopicrorhiza scrophulariiflora (Scrophulariaceae), along with two known iridoid glycosides, picrosides I (5) and II (6), and three known cucurbitacin glycosides (7-9). Their structures were elucidated on the basis of both chemical and spectroscopic data.     

Seasonal variation in antioxidant enzymes and the sprouting response of Gmelina arborea Roxb. nodal sectors cultured in vitro

Nodal sector explants of Gmelina arborea Roxb. showed seasonal variation in the sprouting of axillary buds in vitro. Explants from mature trees showed only 20% sprouting in summer, while those from seedlings and young trees showed over 85% sprouting in this season. In winter, there was a significant decrease in the sprouting response of explants from young and mature trees but not in that of seedling explants. We have attempted to correlate the sprouting response of the explants with their antioxidant status. Activities of three enzymes, namely ascorbate peroxidase, superoxide dismutase and guaiacol-dependent peroxidase which form a part of the antioxidant defense system of plants, were studied in the excised nodal sectors before and after placing them on culture medium. Prior to culture, higher activities of ascorbate peroxidase, superoxide dismutase and guaiacol-dependent peroxidase were observed during winter than during summer. During the culture period, ascorbate peroxidase, superoxide dismutase and guaiacol-dependent peroxidase showed variation depending on the season in which the explants were isolated, and the age of the donor. Axillary bud sprouting in vitro appeared to depend more on the physiological state of the donor, than on the oxidative stress generated during culture. This revised version was published online in June 2006 with corrections to the Cover Date.     

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.     

Flavonol and iridoid glycosides of Ajuga remota aerial parts

Six flavonol glycosides characterised as myricetin 3-O-alpha-rhamnosyl-(1'-->2')-alpha-rhamnoside-3'-O-alpha-rhamnoside, 5'-O-methylmyricetin 3-O-[alpha-rhamnosyl (1'-->2')][alpha-rhamnosyl (1'-->4')]-beta -glucoside-3'-O-beta-glucoside, 5'-O-methylmyricetin 3-O-alpha-rhamnosyl (1'-->2')-alpha-rhamnoside 3'-O-beta-galactoside, kaemferol 3-O-rutinoside-7-O-rutinoside, myricetin 3-O-rutinoside-3'-O-alpha-rhamnoside, myricetin 3-O-beta-glucosyl (1'-->2')-beta-glucoside-4'-O-beta-glucoside together with two iridoid glycosides identified as 6,8-diacetylharpagide and 6,8-diacetylharpagide-1-O-beta-(3',4'-di-O-acetylglucoside) have been isolated from extract of Ajuga remota aerial parts. Also isolated from the same extract were known compounds; kaempferol 3-O-alpha-rhamnoside, quercetin 3-O-beta-glucoside, quercetin 3-O-rutinoside, 8-acetylharpagide, ajugarin I and ajugarin II.     

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.     

Phenolic and iridoid glycosides from Strychnos axillaris

Five phenolic glycosides 1-5 and an iridoid glucoside 6 were isolated, together with 22 known compounds, from the dried barks and woods of Strychnosaxillaris. Their structures were determined by application of spectroscopic (NMR, MS) and chemical methodologies.     

Iridoid glycosides from Gardeniae Fructus for treatment of ankle sprain

The iridoid glycosides, genipin 1-O-β-d-isomaltoside (1) and genipin 1,10-di-O-β-d-glucopyranoside (2), together with six known iridoid glycosides, genipin 1-O-β-d-gentiobioside (3), geniposide (4), scandoside methyl ester (5), deacetylasperulosidic acid methyl ester (6), 6-O-methyldeacetylasperulosidic acid methyl ester (7), and gardenoside (8) were isolated from an EtOH extract of Gardeniae Fructus. The structures and relative stereochemistries of the metabolites were elucidated on the basis of 1D- and 2D-NMR spectroscopic techniques, high-resolution mass spectrometry, and chemical evidence. Geniposide (4), one of the main compounds of Gardeniae Fructus, was tested for treatment of ankle sprain using an ankle sprain model in rats. From the second to fifth day, the geniposide (4) (100 mg/ml) treated group exhibited significant differences (p < 0.01) with ∼21-34% reduction in swelling ratio compared with those of the vehicle treated control group. This indicated the potential effect of geniposide (4) for the treatment of disorders such as ankle sprain.     

Displacement of an herbaceous plant species community by mycorrhizal and non-mycorrhizal Gmelina arborea, an exotic tree, grown in a microcosm experiment

Gmelina arborea Roxb. (Gmelina, Yemane) is a fast growing tree, native from India and considered as a potentially invasive woody plant in West Africa. Mycorrhizal inoculation of seedlings with Glomus intraradices was performed to study (1) the effect on the growth of G. arborea, (2) the impact on the catabolic diversity of soil microbial communities and (3) the influence on the structure of herbaceous plant species communities in microcosms. Treatments consisted of control plants, pre-planting fertilizer application and arbuscular mycorrhizal (AM) inoculation. After 4 months’ culture in autoclaved soil, G. arborea seedlings were either harvested for growth measurement or transferred into containers filled with the same soil but not sterilized. Other containers were kept without G. arborea seedlings. After 12 months’ further culture, effects of fertilizer amendment and AM inoculation on the growth of G. arborea seedlings were recorded. AM colonization was significantly and positively correlated with plant diversity. The substrate-induced respiration response to carboxylic acids was significantly higher in the absence of G. arborea and in the presence of G. intraradices as compared to the other treatments. The influence of AM symbiosis on plant coexistence and on allelopathic processes of invasive plants are discussed.     

Aragoside and iridoid glucosides from Aragoa cundinamarcensis

From the water-soluble part of an extract of Aragoa cundinamarcensis were isolated seven iridoid glucosides, namely aucubin, catalpol, rehmannioside D, globularin, gardoside methyl ester, epiloganin and mussaenoside. The main glycoside isolated, however, was a new caffeoyl phenylethanoid triglycoside, named aragoside, containing two beta-gluco- and one alpha-arabinopyranosyl moieties which constituted almost 5% of the dry weight of the plant. Finally, sorbitol was found to be the main carbohydrate constituent of the plant. This distinctive combination of compounds is very similar to that reported from some species of Plantago. The present findings therefore support the results from a recently published molecular phylogenetic study of plastid and nuclear ribosomal DNA sequences, where Aragoa was found to be the closest relative to Plantago so far discovered.     

Monoterpene glycosides isolated from Fadogia agrestis

Six monoterpene glycosides were isolated from Fadogia agrestis. Their structures were elucidated using a combination of mass spectroscopy, 1D- and 2D-homo- and hetero-NMR spectroscopy and chemical analysis, and established as being derivatives of 2,6-dimethyl-2(E),6(Z)-octadiene-1,8-diol containing from two to four units of rhamnopyranose and, three of them, one or two additional units of glucopyranose. In three of the compounds an acyl group of 8-hydroxy-2,6-dimethyl-2(E),6(Z)-octadienoyl was found esterifying the O-2 position of one of the units of rhamnopyranose.     

Steroidal glycosides from Ruscus ponticus

A comparative metabolite profiling of the underground parts and leaves of Ruscus ponticus was obtained by an HPLC-ESIMSⁿ method, based on high-performance liquid chromatography coupled to electrospray positive ionization multistage ion trap mass spectrometry. The careful study of HPLC-ESIMSⁿ fragmentation pattern of each chromatographic peak, in particular the identification of diagnostic product ions, allowed us to get a rapid screening of saponins belonging to different classes, such as dehydrated/or not furostanol, spirostanol and pregnane glycosides, and to promptly highlight similarities and differences between the two plant parts. This approach, followed by isolation and structure elucidation by 1D- and 2D-NMR experiments, led to the identification of eleven saponins from the underground parts, of which two dehydrated furostanol glycosides and one new vespertilin derivative, and nine saponins from R. ponticus leaves, never reported previously. The achieved results highlighted a clean prevalence of furostanol glycoside derivatives in R. ponticus leaves rather in the underground parts of the plant, which showed a wider structure variety. In particular, the occurrence of dehydrated furostanol derivatives, for the first time isolated from a Ruscus species, is an unusual finding which makes unique the saponins profile of R. ponticus.