Antioxidative iridoid glycosides from the sky flower (Duranta repens Linn)

Phytochemical investigations were performed on the EtOAc-soluble fraction of the whole plant of the sky flower (Duranta repens) which led to the isolation of the iridoid glycosides 1–6. Their structures were elucidated by both 1D and 2D NMR spectroscopic analysis. All the compounds showed potent antioxidative scavenging activity in four different tests, with half maximal inhibitory concentration (IC₅₀) values in the range 0.481–0.719?mM against DPPH radicals, 4.07–17.21 µM for the hydroxyl radical (^?OH) inhibitory activity test, 43.3–97.37 µM in the total reactive oxygen species (ROS) inhibitory activity test, and 3.39–18.94 µM in the peroxynitrite (ONOO^?) scavenging activity test. Duranterectoside A (1) displayed the strongest scavenging potential with IC₅₀ values of (0.481?±?0.06?mM, 4.07?±?0.03, 43.30?±?0.05, 3.39?±?0.02?µM) for the DPPH radicals, ^?OH inhibitory activity test, total ROS inhibitory activity test and the ONOO^? scavenging activity test, respectively.     

Two new anti-plasmodial flavonoid glycosides from Duranta repens

The CHCl₃-soluble fraction of the whole plant of Duranta repens showed anti-plasmodial activity against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum, with IC₅₀ values of 8.5?±?0.9 and 10.2?±?1.5?μg/mL, respectively. From this fraction, two new flavonoid glycosides, 7-O-α-d-glucopyranosyl-3,4′-dihydroxy-3′-(4-hydroxy-3-methylbutyl)-5,6-dimethoxyflavone (1) and 7-O-α-d-glucopyranosyl(6′′′-p-hydroxcinnamoyl)-3,4′-dihydroxy-3′-(4-hydroxy-3-methylbutyl)-5,6-dimethoxyflavone (2), along with five known flavonoids, 3,7,4′-trihydroxy-3′-(4-hydroxy-3-methylbutyl)-5,6-dimethoxyflavone (3), 3,7-dihydroxy-3′-(4-hydroxy-3-methylbutyl)-5,6,4′-trimethoxyflavone (4), 5,7-dihydroxy-3′-(2-hydroxy-3-methyl-3-butenyl)-3,6,4′-trimethoxyflavone (5), 3,7-dihydroxy-3′-(2-hydroxy-3-methyl-3-buten-yl)-5,6,4′-trimethoxyflavone (6), and 7-O-α-d-glucopyranosyl-3,5-dihydroxy-3′-(4′′-acetoxy-3′′-methylbutyl)-6,4′-dimethoxyflavone (7), have been isolated as anti-plasmodial principles. Their structures were deduced by spectroscopic analysis including 1D and 2D NMR techniques. The compounds (1–7) showed potent anti-plasmodial activities against D6 and W2 strains of Plasmodium falciparum, with IC₅₀ values in the range of 5.2–13.5?μM and 5.9–13.1?μM, respectively.     

Repenins A–D,four new antioxidative coumarinolignoids from Duranta repens Linn.

Phytochemical investigations on the CHCl₃-soluble fraction of the whole plant of Duranta repens Linn. led to the isolation of four new coumarinolignoids, Repenins A–D (1–4), along with the known coumarinolignoids, cleomiscosin A (5) and durantin A (6). Their structures were determined by modern spectroscopic analysis including 1D and 2D NMR techniques and chemical studies. The compounds (1–6) showed potent antioxidative scavenging activity against DPPH radicals, with IC₅₀ values in the range 0.420–0.625 mM. Repenin B (2) displayed the strongest scavenging potential with IC₅₀ values of (0.420 mM).     

Two iridoid glycosides from Campsidium valdivianum

Besides stansioside and plantarenaloside, the aerial parts of Campsidium valdivianum contain two new iridoid diglucosides, stansiosigenin 1-O-β-gentiobioside and plantarenalosigenin 1-O-β-gentiobioside.     

4'-deoxy iridoid glycosides from Centranthus longiflorus

The new iridoid glycosides, 4'-deoxykanokoside A and 4'-deoxykanokoside C, were isolated from the methanolic root extract of Centranthus longiflorus ssp. longiflorus. They were accompanied by the three known iridoid glycosides, kanokoside A, kanokoside C and valerosidatum, and two known phenylpropanoid glycosides, coniferin and isoconiferinoside. The structures were elucidated mainly by spectroscopic methods. The presence of 4-deoxy glucose as a part of plant glycosides is rather unusual. Cytotoxic effects of the isolated compounds were also investigated.     

Tetrahydroisoquinoline-monoterpene and iridoid glycosides from Alangium lamarckii

From the water soluble fraction of the dried fruits of Alangium lamrckii, four tetrahydroisoquinoline-monoterpene glycosides, 6-O-methyl-N-deacetylisoipecosidic acid, 7-O-methyl-N-deacetylisoipecosidic acid, 6,7-di-O-methyl-N-deacetylisoipecosidic acid and 6"-O-alpha-D-glucopyranosyl-6-O-methyl-N-deacetylisoipecosidic acid, and an iridoid glycoside, 6'-O-alpha-D-glucopyranosylloganic acid, were isolated, together with six known compounds. The structures of the previously unknown compounds were determined by spectroscopic and chemical means. The significance of these glucosides in the biogenesis of Alangium alkaloids is discussed; 6-O-methyl-N-deacetylisoipecosidic acid was also chemically converted into 10-O-demethylprotoemetine and dihydroisoalangine.     

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.     

Sesquiterpenoids and iridoid glycosides from Valeriana fauriei.

A new guaiane sesquiterpenoid glycoside together with known sesquiterpenoids and iridoid glycosides have been isolated from the rhizomes and roots of Valeriana fauriei. The 13C NMR assignments of the isolated compounds are presented.     

Phenylpropanoid and iridoid glycosides from Pedicularis striata.

A new phenylpropanoid glycoside, pedicularioside A, and five known glycosides, acteoside, isoacteoside, decaffeoylacteoside, echinacoside and 8-acetylharpagide, were isolated from whole plants of Pedicularis striata. On the basis of spectral and chemical evidence, pedicularioside A was shown to be 1'-O-beta-D-(3,4-dihydroxy-beta-phenyl)-ethyl-4'-O-caffeoyl-beta-D -apiosyl-(1----3')-alpha-L-rhamnosyl-(1----6')-glucopyranosi de.     

Phenylpropanoid and iridoid glycosides from Pedicularis spicata.

One new phenylpropanoid glycoside, pedicularioside H, and five known glycosides, gardoside methyl ester, shanzhiside methyl ester, 5-deoxypulchelloside I, verbascoside and pedicularioside A, were isolated from whole plants of Pedicularis spicata. On the basis of the spectral data, chemical evidence and comparison with authentic samples, pedicularioside H was determined to be 1'-O-beta-D-(3-methoxy-4-hydroxy-beta-phenyl)-ethyl-4'-O-feruloyl- beta-D- apiosyl(1----3')-alpha-L-rhamnosyl-(1----6')-glucopyranoside .     

Anti-inflammatory iridoid glycosides from fruits of Cornus officinalis

Three undescribed iridoid glycosides, cyc(7β-O-6′)-morroniside (1), 6′-methyl succinate-7β-O-methylmorroniside (2), and 7β-O-methyl phenyllactate morroniside (3) were isolated from 50% ethanol extract of Cornus officinalis fruits. The structures of the isolated compounds were determined by HRESIMS, ¹D NMR, ²D NMR, UV and IR spectroscopic methods. Compounds 1-3 exhibited moderate anti-inflammatory activities in vivo in a CuSO₄-induced zebrafish inflammation model (when evaluated at 50 μM).     

Three iridoid glycosides from Viburnum furcatum

Three new bitter iridoid glycosides having an 8,10,11-oxygen substituted iridoid skeleton with an isovaleryl moiety at C-1, have been isolated from the ether and ethyl acetate soluble fractions of the leaves of Viburnum furcatum. Two of them had a glucose moiety at C-11 of the iridoid skeleton and a p-coumaroyl group linked to C-6 of the sugar, and they were found to be geometrical isomers about the double bond of the p-coumaroyl2 moiety. The third one was characterized as a alloside of the same aglycone.     

Phenylpropanoid and iridoid glycosides from Pedicularis lasiophrys.

Two new compounds, pedicularioside E and F, were isolated from whole plants of Pedicularis lasiophrys, along with the four known compounds, verbascoside, cistanoside C, cistanoside D and 8-epiloganin. On the basis of spectral and chemical evidence, pedicularioside E and F were identified to be 1'-O-beta-D-(3-methoxy-4-hydroxy-beta-phenyl)-ethyl-6'-O-feruloyl- alpha-L-(2-acetyl)-rhamnosyl-(1----3')-4'-acetylglucopyranoside and shanzhisin methyl ester cellobioside, respectively.     

Ionone,iridoid and phenylethanoid glycosides from Ajuga salicifolia

From the aerial parts of Ajuga salicifolia (L.) Schreber, a new ionone glycoside (3beta-hydroxy-7,8-dihydro-4-oxo-beta-ionol-9-O-beta-D-glucopyranoside) was isolated, along with the known compounds, corchoionoside C, 8-O-acetylmioporoside, ajugol, harpagide, 8-O-acetylharpagide, lavandulifolioside and leonosides A and B. This is the first report of the occurrence of ionone glycosides and 8-O-acetylmioporoside in Ajuga species. Ajugol, lavandulifolioside, leonoside A and B were isolated for the first time from Ajuga salicifolia. The structures were elucidated by means of 1D-, 2D-NMR spectroscopy, and HR-MALDI mass spectrometry.     

Lignan, phenolic and iridoid glycosides from Stereospermum cylindricum

A lignan glycoside [(+)-cycloolivil 4'-O-beta-d-glucopyranoside], a phenolic glycoside [3,4-dimethoxyphenyl 1-O-beta-d-xylopyranosyl-(1-->6)-beta-d-glucopyranoside] and a iridoid glycoside (stereospermoside) were isolated from the leaves and branches of Stereospermum cylindricum, together with (+)-cycloolivil, (+)-cycloolivil 6-O-beta-d-glucopyranoside, (-)-olivil, (-)-olivil 4-O-beta-d-glucopyranoside, (-)-olivil 4'-O-beta-d-glucopyranoside, vanilloloside, decaffeoyl-verbascoside, isoverbascoside, 3,4,5-trimethoxyphenyl 1-O-beta-d-xylopyranosyl-(1-->6)-beta-d-glucopyranoside, ajugol, verminoside, and specioside. The structure elucidations were based on spectroscopic evidence.     

New tetraacetylated iridoid glycosides from Sambucus ebulus L. leaves

Two new minor “Valeriana type” iridoid glycosides (1) and (2) along with 3 known flavonol glycosides [quercetin-3-O-β-glucopyranosyl-7-O-α-rhamnopyranoside (3), quercetin-3-O-β-glucopyranoside (4) and isorhamnetin-3-O-β-glucopyranoside (5)] were isolated from Sambucus ebulus L. leaves. Their structures were unambiguously elucidated by means of 1D- and 2D-NMR, and UPLC-TOF MS. Compound 2 is a rare representative of iridoid diglycosides, containing uncommon ribohexo-3-ulopyranosyl sugar moiety.     

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.     

Secoiridoid glycosides from the flower buds of Lonicera japonica

Two secoiridoid glycosides, loniceracetalides A and B, were isolated in very small amounts, together with 10 known iridoid glycosides, from the flower buds of Lonicera japonica. The structures of loniceracetalides A and B were determined by spectroscopic analysis.     

New iridoid glycosides from the fruits of Forsythia suspensa and their hepatoprotective activities

A novel iridoid glycoside trimer named forsydoitriside A (1) and five new iridoid glycosides (2–6) were isolated from the fruits of Forsythia suspensa together with two known compounds (7, 8). These new structures were elucidated by comprehensive spectroscopic data and the comparison of experimental and calculated electronic circular dichroism spectra. Compounds 1–8 were all assayed on acetaminophen-induced HepG2 cell damage. The results exhibited that compounds 2, 3, 5 and 6 possessed strong hepatoprotective activities against the damage in HepG2 cell.