Newbouldiosides A-C, phenylethanoid glycosides from the stem bark of Newbouldia laevis

From the stem bark of Newbouldia laevis three phenylethanoid glycosides, designated as newbouldioside A-C, were isolated together with a sodium salt of analogue B and the known compounds, verbascoside, 5-hydroxydehydro-iso-alpha-lapachone, 3,8-dihydroxydehydro-iso-alpha-lapachone, apigenin and luteolin. The structures of the phenylethanoid glycosides were elucidated by spectroscopic methods as beta-(3,4-dihydroxyphenyl)ethyl 5-O-syringoyl-beta-D-apiofuranosyloxy-(1-->2)-O-[alpha-L-rhamnopyranosyl-(1-->3)]-beta-D-glucopyranoside, ss-(3,4-dihydroxyphenyl)ethyl 5-O-syringoyl-beta-D-apiofuranosyloxy-(1-->2)-O-[alpha-L-rhamnopyranosyl-(1-->3)]-6-O-E-feruloyl-beta-D-glucopyranoside, and beta-(3,4-dihydroxyphenyl)ethyl 3-O-E-feruloyl-beta-D-apiofuranosyloxy-(1-->2)-O-alpha-L-rhamnopyranosyl-(1-->2)-6-O-E-sinapoyl-beta-D-glucopyranoside, respectively.     

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.     

Cytotoxic phenylethanol glycosides from Psidium guaijava seeds

Phytochemical investigations of the acetone extract of Psidium guaijava seeds has led to the isolation of five known flavonoid glycosides, two phenolic glycosides and two new phenylethanoid glycosides which have been identified as 1-O-3,4-dimethoxy-phenylethyl-4-O-3,4-dimethoxy cinnamoyl-6-O-cinnamoyl-beta-D-glucopyranose and 1-O-3,4-dimethoxyphenylethyl-4-O-3,4-dimethoxy cinnamoyl-beta-D-glucopyranose, on the basis of chemical, physical and spectroscopic methods of analysis.     

Phenylethanoids, iridoids and a spirostanol saponin from Veronica turrilliana

From the aerial parts of Veronica turrilliana two phenylethanoid glycosides, turrilliosides A and B and a steroidal saponin, turrillianoside were isolated and their structures elucidated as beta-(3,4-dihydroxyphenyl)ethyl-4-O-E-caffeoyl-O-[beta-glucopyranosyl-(1-->4)-alpha-rhamnopyranosyl-(1-->6)]-beta-glucopyranoside, beta-(3,4-dihydroxyphenyl)ethyl-4-O-E-caffeoyl-[6-O-E-feruloyl-beta-glucopyranosyl-(1-->4)-alpha-rhamnopyranosyl-(1-->6)]-beta-glucopyranoside and (23S,25S)-12beta,23-dihydroxyspirost-5-en-3beta-yl O-alpha-rhamnopyranosyl-(1-->4)-beta-glucopyranoside, respectively. Furthermore, eight known glucosides are reported namely, catalpol, catalposide, verproside, amphicoside, isovanilloylcatalpol, aucubin, arbutin, and 6-O-E-caffeoylarbutin, the latter two for the first time in the genus Veronica. The two phenylethanoid glycosides were found to be potent DPPH radical scavengers. All of the tested compounds were inactive against the representative species of fungi and bacteria.     

Three acylated flavone glycosides from Sideritis ozturkii Aytac & Aksoy

From the aerial parts of Sideritis ozturkii, three new flavonoids, chrysoeriol 7-O-[2'-O-caffeoyl-O-acetyl-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranoside], chrysoeriol 7-O[2'-O-caffeoyl-beta-D-glucopyranosyl-(1 -->2)-beta-D-glucopyranoside] and chrysoeriol 7-O[2'-O-p-coumaroyl-6'-beta-O-acetyl-D-glucopyranosyl-(1-->2)-beta-D-glucopyranoside] named as ozturkosides A, B and C, respectively, were isolated, along with three known phenylethanoid glycosides, verbascoside, leucoseptoside A, martynoside and five known diterpenoids, 7-epicandicandiol, linearol, sidol, sideroxol, epoxyisolinearol. The structures were elucidated mainly by spectroscopic methods.     

Further constituents from the bark of Tabebuia impetiginosa

Further study on the constituents from the bark of Tabebuia impetiginosa (Mart. ex DC) Standley afforded twelve compounds, consisting of four iridoid glycosides, one phenylethanoid glycoside, five phenolic glycosides, and one lignan glycoside, along with seven known compounds. The structures of these compounds were determined based on the interpretation of their NMR and MS measurements and by chemical evidence.     

Comparative phytochemical characterization of three Rhodiola species

In comparison to the well-recognized adaptogenic herb Rhodiola rosea, phytochemical constituents of two other Rhodiola species (R. heterodonta and R. semenovii) were elucidated and characterized. Two major phytochemical groups; phenolic and/or cyanogenic glycosides and proanthocyanidins, were isolated and identified in the three species. Chemical similarities among the three species were observed; however, each species displayed differences in phytochemical constituents. R. heterodonta contained a newly detected phenylethanoid glycoside, heterodontoside, in addition to the known compounds tyrosol, viridoside, salidroside, and rhodiocyanoside A. Both R. heterodonta and R. rosea contained phenylethanoid/propanoid compounds that were not detected in R. semenovii. For R. semenovii, the cyanogenic glucosides rhodiocyanoside A and lotaustralin were detected. Although the three species have proanthocyanidins composed of (-)-epigallocatechin and its 3-O-gallate esters in common, the degree of polymerization greatly differed between them. In contrast to R. heterodonta and R. semenovii, R. rosea has higher molecular weight polymeric proanthocyanidins. This study resulted in the identification and isolation of phytochemical constituents for direct cross-comparison between three Rhodiola species of medicinal and pharmacological value.     

Cucurbitacins from Bacopa monnieri

Four cucurbitacins, bacobitacin A-D (1-4) as well as, a known cytotoxic, cucurbitacin E (5) together with three known phenylethanoid glycosides, monnieraside I, III and plantioside B were isolated form the aerial part of Bacopa monnieri. Their structures were elucidated on the basis of extensive spectroscopic investigations (1D, 2D NMR and ESI-QTOF-MS/MS). This is the first report on the characterization of cucurbitacins in B. monnieri.     

Effect of chito-oligosaccharide on the intestinal absorptions of phenylethanoid glycosides in Fructus Forsythiae extract

Phenylethanoid glycosides, the main active ingredients in Fructus Forsythiae extract possesses strong antibacterial, antioxidant and antiviral effects, and their contents were higher largely than that of other ingredients such as lignans and flavones, but their absolute bioavailability orally was significantly low, which influenced clinical efficacies of its oral preparations seriously. In the present study, the absorption mechanism of phenylethanoid glycosides was studied using in vitro Caco-2 cell model. And the effect of chito-oligosaccharide (COS) on the intestinal absorption of phenylethanoid glycosides in Fructus Forsythiae extract was investigated using in vitro, in situ and in vivo models. The pharmacological effects such as antiviral activity improvement by COS were verified by MDCK cell damage inhibition rate after influenza virus propagation. The observations from in vitro Caco-2 cell showed that the absorption of phenylethanoid glycosides in Fructus Forsythiae extract so with that in monomers was mainly restricted by the tight junctions, and influenced by efflux transporters (P-gp and MRP2). Meanwhile, the absorption of phenylethanoid glycosides in Fructus Forsythiae extract could be improved by COS. Besides, COS at the same low, medium and high concentrations caused a significant, concentration-dependent increase in the P_app-value for phenylethanoid glycosides compared to the control group (p < 0.05), and was all safe for the Caco-2 cells. The observations from single-pass intestinal perfusion in situ model showed that the intestinal absorption of phenylethanoid glycosides can be enhanced by COS. Meanwhile, the absorption enhancing effect of phenylethanoid glycosides might be saturable in different intestine sites. In pharmacokinetics study, COS at dosage of 25 mg/kg improved the bioavailability of phenylethanoid glycosides in Fructus Forsythiae extract to the greatest extent, and was safe for gastrointestine from morphological observation. In addition, treatment with Fructus Forsythiae extract with COS at dosage of 25 mg/kg prevented MDCK cell damage upon influenza virus propagation better than that of control. All findings above suggested that COS at dosage of 25 mg/kg might be safe and effective absorption enhancer for improving the bioavailability of phenylethanoid glycosides and the antiviral activity in vitro in Fructus Forsythiae extract.     

Antioxidant efficacy of iridoid and phenylethanoid glycosides from the medicinal plant Teucrium chamaedris in cell-free systems

Twelve glycosides, seven iridoids and five phenylethanoids, have been isolated from leaf and root methanolic extracts of Wall Germander (Teucrium chamaedrys), a Mediterranean species historically used as a medicinal plant. Among them, three iridoid and one phenylethanoid glycosides have been isolated and characterized for the first time. All of the structures have been elucidated on the basis of their spectral data, especially 1D and 2D NMR experiments.The antioxidative properties of pure metabolites, as well as of crude organic extracts of the plant, have been analyzed on the basis of their DPPH radical scavenging capability. The antioxidant capacity in cell-free systems of the isolated metabolites was carried out by measuring their capabilities to inhibit the synthesis of thiobarbituric acid reactive species in assay media using as oxidable substrates a vegetable fat and the pentose sugar 2-deoxyribose and to prevent oxidative damage of the hydrosoluble bovine serum albumin (BSA) protein. Phenylethanoid glycosides resulted efficacious DPPH radical, while iridoid glycosides prevent massively the 2-deoxyribose and BSA oxidations in assay media.     

Constituents from the bark of Tabebuia impetiginosa

The bark of Tabebuia impetiginosa afforded nineteen glycosides, consisting of four iridoid glycosides, two lignan glycosides, two isocoumarin glycosides, three phenylethanoid glycosides and eight phenolic glycosides. Their structures were determined using both spectroscopic and chemical methods. Iridoid glycosides, phenylethanoid glycosides and lignan glycosides had ajugol, osmanthuside H and secoisolariciresinol 4-O-beta-D-glucopyranoside as their structural elements, respectively, whereas the aglycone moieties of the isocoumarin glycosides were considered to be (-)-6-hydroxymellein. Phenolic glycosides had 4-methoxyphenol, 2,4-dimethoxyphenol, 3,4-dimethoxyphenol, 3,4,5-trimethoxyphenol and vanillyl 4-hydroxybenzoate as each aglycone moiety. Additionally, the sugar chains of these isocoumarin glycosides and phenolic glycosides were concluded to be beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranoside as well as those of osmanthuside H and above phenylethanoid glycosides.     

Phenylethanoid Glycosides from Picria felterrae Lour.

In our search for bioactive compounds from the whole plant of Picriafelterrae Lour., three new phenylethanoid glycosides, picfeosides A-C (1-3), along with five known phenylethanoid glycosides,namely wiedemannioside (4), acteoside (5), acteoside isomer (6), cis-acteoside isomer (7), and cis-acteoside (8), were isolated using several chromatographic purification steps, including semipreparation HPLC on RP-18. The structures of the new compounds were elucidated on the basis of extensive spectroscopic analysis.     

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.     

Phenylethanoid Glycosides from Picria felterrae Lour.

In our search for bioactive compounds from the whole plant of Picriafelterrae Lour., three new phenylethanoid glycosides, picfeosides A-C (1-3), along with five known phenylethanoid glycosides,namely wiedemannioside (4), acteoside (5), acteoside isomer (6), cis-acteoside isomer (7), and cis-acteoside (8), were isolated using several chromatographic purification steps, including semipreparation HPLC on RP-18. The structures of the new compounds were elucidated on the basis of extensive spectroscopic analysis.     

Identification of tyrosinase inhibitors from Marrubium velutinum and Marrubium cylleneum

Tyrosinase is a key enzyme in the production of melanins in plants and animals. Forty-five secondary metabolites isolated from Marrubium velutinum and Marrubium cylleneum belonging to the classes of flavonoids, phenylethanoid glycosides, phenolic acids and lignan glycosides were screened for their inhibitory activity against mushroom tyrosinase. Flavonoids and phenylethanoid glycosides showed moderate inhibitory activity, while phenolic acids were less active than phenylethanoid glycosides, suggesting that both phenolic groups are important for the activity.     

Iridoids from Scutellaria albida ssp. albida

Three iridoid glycosides, 6'-O-E-p-coumaroylgardoside (1), 6'-O-p-E-coumaroyl-8-epi-loganic acid (2) and scutelloside (3) were isolated from the aerial parts of Scutellaria albida subsp. albida, in addition to an anomeric mixture in equilibrium of one iridoid aglycone (4, 4a), nine iridoid glycosides (5-13), four known phenylethanoid glycosides (14-17), and six known phenolic derivatives (18-23).     

Secondary metabolites from Centaurea ensiformis P.H. Davis

Centaurea ensiformis P.H. Davis was evaluated for its secondary metabolites. 20 different compounds have been isolated and identified; four phenolic compounds, one aminoacid, two acetophenone glycosides, three phenylpropanoide glycosides, one coumarin glucoside, four flavon glycosides, two neolignan glycosides, two megastigmane glycosides and schikimic acid methyl ester.     

Phenylethanoid and lignan glycosides from Verbascum thapsus.

Verbascum thapsus afforded, in addition to three known phenylethanoid glycosides and four lignan ones, five new phenylethanoid glycosides and one new lignan glycoside. Structures of the compounds were elucidated by spectroscopic methods and chemical evidence.     

Tyrosinase Inhibitors from the Aerial Parts of Wulfenia carinthiaca Jacq.

Activity guided isolation of a MeOH extract of the aerial plant parts of Wulfenia carinthiaca Jacq . (Plantaginaceae), using a mushroom tyrosinase assay, resulted in the isolation of five phenylethanoid glucosides and four iridoid glycosides. Two of them, 2′‐O‐acetylisoplantamajoside and 2′,6″‐O‐diacetylisoplantamajoside, represent new natural products. Evaluation of the inhibitory activity of all isolated compounds revealed that the observed activity is not related to the isolated phenylethanoid glycosides but mainly due to the presence of the iridoid glycoside globularin (IC₅₀ 41.94 μm ; CI_95% ± 16.61/11.89 μm ). Interestingly, structurally close related compounds (globularicisin, baldaccioside, and isoscrophularioside) showed no or only a weak tyrosinase inhibitory activity.