Isolation and absolute structures of enantiomeric 1,2-bis(4-hydroxy-3-methoxyphenyl)-1,3-propanediol 1-O-glucosides from the bark of Hovenia trichocarpa

Structurally diverse 1,2-diarylpropanes from the fruit of Crataegus pinnatifida and the investigation on their mirror-image ECD spectra with the same absolute configurations

1,2-diarylpropanes are a kind of abundant natural products formed by radical coupling. On account of molecular flexibility, it was challenged in the identifications of relative and absolute configurations of the 1,2-diarylpropanes. In this research, fourteen pairs of enantiomeric 1,2-diarylpropanes (1a/1b-14a/14b), comprising twelve previously undescribed pairs (1a/1b-4a/4b, 6a/6b-10a/10b, and 12a/12b-14a/14b), were isolated from the fruit of Crataegus pinnatifida. Their structures were determined through multiple NMR spectral analyses, empirical NMR rules, X-ray crystallography, and the comparison of experimental ECD spectra with calculated data. In addition, the analysis of ECD spectra revealed that substituent effects could generate an inverted chiroptical response, exhibiting in mirror-image ECD signals. This phenomenon was investigated by conformational analysis, molecular orbital analysis, the transition density matrix and hole/electron distributions. Moreover, a potential experimental rule was proposed for the rapid determination of the absolute configurations of the 1,2-diarylpropanes.

Neuroprotective Alkamides from the Aerial Parts of Achillea alpina L

Three new alkamides, achilleamide B-D (1-3) along with five known alkamides (4-8) were isolated from the aerial parts of Achillea alpina L. Structures were elucidated by spectroscopic analysis. Modified Mosher's method and electronic circular dichroism (ECD) calculations were introduced for the absolute configuration of 3. The neuroprotective effects of all the compounds were evaluated by 6-hydroxydopamine (6-OHDA)-induced cell death in human neuroblastoma SH-SY5Y cells, with concentration for 50 % of maximal effect (EC₅₀ ) values of 3.16-24.75 μM, and the structure-activity relationship was conducted.

Rapid Approaches for Assignment of the Relative Configuration in 1-Oxygenated 1,2-Diarylpropan-3-ols by 1H NMR Spectroscopy

The structural elucidation of chiral molecules with more than one stereocenter is usually a tricky problem. In this paper, efficient ¹H NMR spectroscopic approaches for assigning the erythro and threo configurations of 1-oxygenated 1,2-diarylpropan-3-ols were developed. By analysis of the chemical shift differences of diastereotopic methylene H₂-3 (Δδ₃) in CDCl₃ or the chemical shift differences of H-1 and H-2 (Δδ_1,2) in methanol-d₄, deuterated dimethyl sulfoxide, and acetone-d₆, the configurations of 1-oxygenated 1,2-diarylpropan-3-ols can be rapidly and conveniently determined.

Chemical constituents of the root bark of Ulmus davidiana var. japonica and their potential biological activities

The root bark of Ulmus davidiana var. japonica (Ulmaceae), commonly known as yugeunpi, has been used as a traditional Korean medicine for the treatment of gastroenteric and inflammatory disorders. As part of continuing projects to discover bioactive natural products from traditional medicinal plants with pharmacological potential, phytochemical investigation of the root bark of this plant was carried out. This led to the successful isolation of a new chromane derivative (1) and 22 known compounds: catechin derivatives (2-5), megastigmane glycoside (6), dihydrochalcone glycosides (7 and 8), flavanone glycosides (9 and 10), coumarins (11 and 12), lignan derivatives (13-17), and phenolic compounds (18-23). The structure of the new compound (1) was determined with 1D and 2D NMR spectroscopy and HR-ESIMS, and its absolute configurations were achieved by chemical reactions and the gauge-including atomic orbital (GIAO) NMR chemical shifts calculations. All the isolated compounds were evaluated for their potential biological activities including neuro-protective, anti-neuroinflammatory, and anti-Helicobacter pylori activities. Among the isolates, compounds 1, 8, and 20 displayed stronger potency by causing a greater increase in the production and the activity of nerve growth factor (NGF) in C6 glioma cells (147.04 ± 4.87, 206.27 ± 6.70, and 143.70 ± 0.88%, respectively), whereas compounds 11, 14, and 19 inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated murine microglial cells (IC₅₀ of 18.72, 12.31, and, 21.40 µM, respectively). In addition, compounds 1, 11, 18, and 20 showed anti-H. pylori activity with MIC values of 25 or 50 µM against two strains of H. pylori 51 and 43504. These findings provide scientific evidence that supports the traditional usage of U. davidiana var. japonica root bark in the treatment of gastroenteric and inflammatory disorders.

Anti-inflammatory lignans and phenylethanoid glycosides from the root of Isodon ternifolius (D.Don) Kudô

Five undescribed lignans, three undescribed phenylethanoid glycosides and eight known compounds were isolated from the root of Isodon ternifolius (D.Don) Kudô (Lamiaceae). The structures of all of the isolated constituents were characterized by physical data analyses including NMR, MS and ECD. The anti-inflammatory activities of the isolates were evaluated based on their ability to inhibit NO, PGE2 and TNF-α production in LPS-induced RAW 264.7 macrophage cells. Six phenyl-naphthalene lignans, ternifoliuslignan A, ternifoliuslignan B, ternifoliuslignan C, ternifoliuslignan D, ternifoliuslignan E and 3-carboxy-6,7-dihydroxy-1-(3',4'-dihydroxyphenyl) -naphthalene, can substantially inhibit the release of NO with IC₅₀ values in the range of 9.98-29.14 μM, which are better than the positive reference. These phenyl-naphthalene lignans could markedly decrease the secretions of PGE2 and TNF-α in LPS-induced RAW264.7 cells. Ternifoliuslignan C and ternifoliuslignan D decreased iNOS, COX-2 and NF-κB/p65 protein expression. A preliminary structure-activity relationship among the phenyl-naphthalene lignans for the anti-inflammatory activity was discussed.

Two pairs of phenolic enantiomers from the leaves of Eucommia ulmoides Oliver

Two pairs of new phenolic enantiomers, (+)-eucophenolic A (1a), (-)-eucophenolic B (1b), (-)-eucophenolic C (2a), (+)-eucophenolic D (2b) were isolated from the leaves of Eucommia ulmodies Oliver by chiral enantiomeric resolution. Their structures were elucidated based on extensive spectroscopic analysis. The absolute configurations of 1a/1b and 2a/2b were determined by empirical method and the calculated ECD and OR. All compounds were tested for Hep G2 tumour cell lines. However, no compounds showed potential cytotoxic activities against Hep G2 in vitro.

Enantiomeric Lignans and Neolignans from Phyllanthus glaucus: Enantioseparation and Their Absolute Configurations

Eight pairs of enantiomeric neolignans, norlignans, and sesquineolignans (1a/1b–8a/8b), together with five known neolignans (9a/9b and 10–12), have been isolated from 70% acetone extract of the whole plants of Phyllanthus glaucus Wall. (Euphorbiaceae). The racemic or partial racemic mixtures were successfully separated by chiral HPLC using different types of chiral columns with various mobile phases. Their structures were elucidated on the basis of extensive spectroscopic data. The absolute configurations of 2a/2b were determined by computational analysis of their electronic circular dichroism (ECD) spectrum, and the absolute configurations of other isolates were ascertained by comparing their experimental ECD spectra and optical rotation values with those of structure-relevant compounds reported in literatures. Compounds 4a/4b featured unique sesquineolignan skeletons with a novel 7-4′-epoxy-8′-8′′/7′-2′′ scaffold, consisting of an aryltetrahydronaphthalene and a dihydrobenzofuran moiety. The planar structures of compounds 2, 3, 7, and 8 were documented previously; however, their absolute configurations were established for the first time in this study. The antioxidant activities of 1a/1b–8a/8b were evaluated using DPPH free radical scavenging assay, and the results demonstrated that compounds 1b and 3b showed potent DPPH radical scavenging activities with IC₅₀ values of 5.987 ± 1.212 and 9.641 ± 0.865 μg/mL, respectively.

A New Steroidal Glycoside and Potential Anticancer Cytotoxic Activity of Compounds Isolated from the Bulbs of Lilium Callosum

Callosum A, a new steroidal glycoside, has been isolated from the n-butanol soluble fraction of Lilium callosum, along with five known steroidal glycosides, reported for the first time from Lilium callosum. Their structures were elucidated on the basis of spectroscopic methods and from literature values. All compounds were tested for anticancer cytotoxic activity against GSC-7901, K562, and SPCA-1 cells.

Lignans from the stems of Clematis armandii ("Chuan-Mu-Tong") and their anti-neuroinflammatory activities

ETHNOPHARMACOLOGICAL RELEVANCE

The dried stems of Clematis armandii (Caulis clematidis armandii), named "Chuan-Mu-Tong" in Chinese Pharmacopoeia, have been traditionally used as an herbal remedy mainly for inflammation-associated diseases. The Aim of the study is to identify the potential anti-neuroinflammatory components from Clematis armandii.

MATERIALS AND METHODS

The ethanol extract of "Chuan-Mu-Tong" was suspended in H₂O and exhaustively extracted with CH₂Cl₂. The CH₂Cl₂ fraction was successively subjected to column chromatography (CC) over silica gel, Sephadex LH-20, and semi-preparative HPLC. The structures of the isolated compounds were identified by spectroscopic methods and by comparison with those reported in the literature. Their anti-neuroinflammatory activities were evaluated by inhibitory effects on pro-inflammatory mediators [e.g. nitric oxide (NO) and tumor necrosis factor-alpha (TNF-α)] in lipopolysaccharide (LPS)-activated BV-2 cells.

RESULTS

One new and sixteen known lignans were isolated and characterized. The absolute configuration of the new lignan, (7R,8S)-9-acetyl-dehydrodiconiferyl alcohol (1), was elucidated by a combination of 1D/2D NMR techniques and the Electronic Circular Dichroism (ECD) spectroscopy based on the empirical helicity rules. The anti-neuroinflammatory bioassay showed that compounds 1, (7R,8S)-dehydrodiconiferyl alcohol (2), erythro-guaiacylglycerol-β-coniferyl ether (5), and threo-guaiacylglycerol-β-coniferyl ether (6) displayed significant inhibitory effects on NO production. Among them, neolignans 1 and 2 exhibited more potent activities than the positive control (N(G)-monomethyl-L-arginine, L-NMMA), with an IC₅₀ value of 9.3 and 3.9 μM, respectively. Moreover, both 1 and 2 were also found to concentration-dependently suppress the TNF-α release in LPS-stimulated BV-2 cells.

CONCLUSION

The results revealed that lignans are the major components of "Chuan-Mu-Tong", and their anti-neuroinflammatory activities strongly support the traditional application of this herb medicine on inflammation. Moreover, the dihydrobenzo[b]furan neolignans 1 and 2 as well as Caulis clematidis armandii could be further exploited as new therapeutic agents to treat inflammation-mediated neurodegenerative and aging-associated diseases.

Five new compounds from Rhododendron mariae Hance

Five new compounds (-)-(7R,8S,7'R,8'S)-4,9,4',9'-tetrahydroxy-3,3'-dimethoxy-7,7'-epoxylignan 9-O-β-d-xylopyranoside (1), (-)-(7'R,8'S)-5'-methoxyl(dimeric coniferyl acetate) (2), (+)-(1R,2S)-1,2-bis(4-hydroxy-3-methoxyphenyl)-3-acetyl-1,3-propanediol (3), (-)-3-((2R,3R)-2-ethoxy-3-(hydroxymethyl)-7-methoxy-2,3-dihydrobenzofuran-5-yl)propan-1-ol (4), and (+)-3-((2S,3S)-2-ethoxy-3-(hydroxymethyl)-7-methoxy-2,3-dihydrobenzofuran-5-yl)propan-1-ol (5), together with 12 known compounds, were isolated from an ethanol extract of the dried stems of Rhododendron mariae Hance. Their structures were elucidated by NMR, HR-MS, CD, ORD experiments and chemical methods. Compounds 2, 3, 6, and 17 exhibited significant inhibitory effects on the nitric oxide production in lipopolysaccharide activated C57BL6/J mouse macrophages.

Two new compounds from Crataegus pinnatifida and their antithrombotic activities

One new sesquiterpene, (1α,4aβ,8aα)-1-isopropanol-4a-methyl-8-methylenedecahydronaphthalene (1), with one new phenylpropanoid, threo-2-(4-hydroxy-3,5-dimethoxyphenyl)-3-(4-hydroxy-3-methoxyphenyl)-3-ethoxypropan-1-ol (2), along with four known phenylpropanoids were isolated from Crataegus pinnatifida. The structures of compounds 1 and 2 were elucidated on the basis of 1D, 2D NMR analyses, and HR-ESI-MS. The antithrombotic activity in vitro of all isolates was assayed, and only compound 1 exhibited potent antithrombotic activity by inhibiting platelet aggregation in rat plasma by 81.4% at 1 mg/ml.

Steroidal and phenolic glycosides from the bulbs of Lilium pumilum DC and their potential Na+/K+ ATPase inhibitory activity

A new steroidal saponin, named pumilum A (1), and a new phenolic glycoside, threo-1-(4′-hydroxy-2′-methoxyphenyl)-2-(2′′,4′′-dihydroxyphenyl)-1,3-propanediol-4′-O-β-D-glucopyranoside (7) were isolated from the methanolic extract of the bulbs of Lilium pumilum DC, along with five known steroidal saponins. Their chemical structures were elucidated on the basis of detailed spectroscopic analysis, including 1D and 2D NMR techniques and chemical methods. In addition, the inhibitory activity of all the isolates on Na⁺/K⁺ ATPase was evaluated.

A new lignan from Oxytropis myriophylla

The 70% alcohol extract of Oxytropis myriophylla (PALL.) DC. (Leguminosae) exhibited high radical scavenging activity (IC(50) value: 88.0 µg mL(-1) and 86.7 µg mL(-1)) on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging assays. Further chemical investigation led the isolation of one new lignan, namely myriophylloside G (1), together with three known compounds. Their structural elucidations of all the compounds were based on extensive spectroscopic methods, including HRESIMS and 2D NMR experiments (HSQC, HMBC and (1)H-(1)HCOSY) and by comparison with reference values.

Further investigation into maple syrup yields 3 new lignans, a new phenylpropanoid, and 26 other phytochemicals

Maple syrup is made by boiling the sap collected from certain maple ( Acer ) species. During this process, phytochemicals naturally present in tree sap are concentrated in maple syrup. Twenty-three phytochemicals from a butanol extract of Canadian maple syrup (MS-BuOH) had previously been reported; this paper reports the isolation and identification of 30 additional compounds (1-30) from its ethyl acetate extract (MS-EtOAc) not previously reported from MS-BuOH. Of these, 4 compounds are new (1-3, 18) and 20 compounds (4-7, 10-12, 14-17, 19, 20, 22-24, 26, and 28-30) are being reported from maple syrup for the first time. The new compounds include 3 lignans and 1 phenylpropanoid: 5-(3″,4″-dimethoxyphenyl)-3-hydroxy-3-(4'-hydroxy-3'-methoxybenzyl)-4-(hydroxymethyl)dihydrofuran-2-one (1), (erythro,erythro)-1-[4-[2-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-1-(hydroxymethyl)ethoxy]-3,5-dimethoxyphenyl]-1,2,3-propanetriol (2), (erythro,threo)-1-[4-[2-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-1-(hydroxymethyl)ethoxy]-3,5-dimethoxyphenyl]-1,2,3-propanetriol (3), and 2,3-dihydroxy-1-(3,4- dihydroxyphenyl)-1-propanone (18), respectively. In addition, 25 other phenolic compounds were isolated including (threo,erythro)-1-[4-[(2-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-1-(hydroxymethyl)ethoxy]-3-methoxyphenyl]-1,2,3-propanetriol (4), (threo,threo)-1-[4-[(2-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-1-(hydroxymethyl)ethoxy]-3-methoxyphenyl]-1,2,3-propanetriol (5), threo-guaiacylglycerol-β-O-4'-dihydroconiferyl alcohol (6), erythro-1-(4-hydroxy-3-methoxyphenyl)-2-[4-(3-hydroxypropyl)-2,6-dimethoxyphenoxy]-1,3-propanediol (7), 2-[4-[2,3-dihydro-3-(hydroxymethyl)-5-(3-hydroxypropyl)-7-methoxy-2-benzofuranyl]-2,6-dimethoxyphenoxy]-1-(4-hydroxy-3-methoxyphenyl)-1,3-propanediol (8), acernikol (9), leptolepisol D (10), buddlenol E (11), (1S,2R)-2-[2,6-dimethoxy-4-[(1S,3aR,4S,6aR)-tetrahydro-4-(4-hydroxy-3,5-dimethoxyphenyl)-1H,3H-furo[3,4-c]furan-1-yl]phenoxy]-1-(4-hydroxy-3-methoxyphenyl)-1,3-propanediol (12), syringaresinol (13), isolariciresinol (14), icariside E4 (15), sakuraresinol (16), 1,2-diguaiacyl-1,3-propanediol (17), 2,3-dihydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl)-1-propanone (19), 3-hydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl)propan-1-one (20), dihydroconiferyl alcohol (21), 4-acetylcatechol (22), 3',4',5'-trihydroxyacetophenone (23), 3,4-dihydroxy-2-methylbenzaldehyde (24), protocatechuic acid (25), 4-(dimethoxymethyl)pyrocatechol (26), tyrosol (27), isofraxidin (28), and 4-hydroxycatechol (29). One sesquiterpene, phaseic acid (30), which is a known metabolite of the phytohormone abscisic acid, was also isolated from MS-EtOAc. The antioxidant activities of MS-EtOAc (IC(50) = 75.5 μg/mL) and the pure isolates (IC(50) ca. 68-3000 μM) were comparable to that of vitamin C (IC(50) = 40 μM) and the synthetic commercial antioxidant butylated hydroxytoluene (IC(50) = 3000 μM), in the diphenylpicrylhydrazyl radical scavenging assay. The current study advances scientific knowledge of maple syrup constituents and suggests that these diverse phytochemicals may impart potential health benefits to this natural sweetener.

A new pregnane steroid from Poria cum radix pini

A new pregnane steroid and eight known compounds were isolated from Poria cum radix pini. Their structures were identified by spectroscopic data. All the known compounds were isolated from this species for the first time.

Water-soluble constituents from the bark of Elaeagnus pungens and their cytotoxic activities

Three new water-soluble compounds, pungens A-C, along with four known compounds including two phenol glycosides, one secoiso-flavanol and one phenol ether, have been isolated from the bark of Elaeagnus pungens. Among them, pungen C (7) (200 microg/ml) was tested in SGC-7901 and BEL-7404 tumor cell lines, and showed moderate cytotoxic activity. The structures of the new compounds were elucidated on the basis of spectroscopic data and chemical evidence.

Lignans from the stems of Sambucus williamsii and their effects on osteoblastic UMR106 cells

Three new lignans, sambucunol A (8) ((+)-erythro-1-(4-hydroxy-3-methoxyphenyl)-2-[4-(4-hydroxy-3-methoxycinnamoyloxypropanyl)-2-hydroxyphenoxy]-1, 3-propanediol), sambucunol B (9) ((+)-threo-1-(4-hydroxyl-3-methoxyphenyl)-2-[4-(4-hydroxy-3-methoxy-cinnamoyloxy propanyl)-2-hydroxyphenoxy]-1, 3-propanediol) and buddlenol G (10) (2-{4-[2, 3-dihydro-3-hydroxymethyl-7-hydroxy-5-(4-hydroxy-3-methoxycinnamoyloxypropanyl)-2-benzofuranyl]-2,6-dimethoxyphenoxy}-1-(4- hydroxy-3-methoxyphenyl) -1, 3-propanediol), along with seven known ones, including ( - )-syringaresinol (1), ( - )-pinoresinol (2), 1, 2-bis(4-hydroxy-3-methoxy phenyl)-1, 3-propanediol (3), ( - )-erythro-1-(4-hydroxy-3-methoxyphenyl)-2-[4-(3-hydroxy propanyl)-2-methoxyphenoxy]-1, 3-propanediol (4), ( - )-threo-1-(4-hydroxy-3-methoxyphenyl)-2-[4-(3-hydroxypropanyl)-2-methoxy phenoxy]-1, 3-propanediol (5), ( - )-lariciresinol (6) and ( - )-dihydrodehydrodiconiferyl alcohol (7), were isolated from the 60% ethanol extract of stems of Sambucus williamsii Hance by chromatographic methods. Their structures were established by spectral analysis. The effects of isolated compounds on the osteoblast-like UMR106 cell proliferation and ALP activities were determined. Compounds 2, 7 and 10 showed stimulating effects both on UMR106 cell proliferation and ALP activity. Compounds 1, 3, 6 and 8 stimulated UMR106 cell proliferation, while compounds 4 and 5 induced ALP activity in UMR106 cell.

Lignans from Arctium lappa and Their Inhibition of LPS-Induced Nitric Oxide Production

A new butyrolactone sesquilignan, isolappaol C (1), together with four known lignans, lappaol C (2), lappaol D (3), lappaol F (4), and diarctigenin (5), were isolated from the methanolic extract of the seeds from the Arctium lappa plant. The structure of isolappaol C (1) was determined by spectral analysis including 1D- and 2D-NMR. All the isolates were evaluated for their inhibitory effects on the LPS-induced nitric oxide production using murine macrophage RAW264.7 cells. Lappaol F (4) and diarctigenin (5) strongly inhibited NO production in the LPS-stimulated RAW264.7 cells with IC(50) values of 9.5 and 9.6 microM, respectively.

Constituents from the Bark of Tabebuia impetiginosa

Thirteen new phenolic glycosides were obtained by further study of constituents from the bark of Tabebuia impetiginosa (MART. ex DC) Standley (Bignoniaceae). The structures of these compounds were determined based on NMR, mass spectral and chemical evidence. Most of them have a glycosyl unit esterified by a benzoic acid derivative.

New phenolics from the roots of Symplocos caudata Wall

Three new phenolics, (1S,2R)-1-(4'-O-beta-D-glucopyranosyl-3'-methoxyphenyl)-2-(4''-hydroxy-3''-methoxyphenyl)-1,3-propanediol, symplolignanoside A, and 3,4-dimethoxyphenol beta-D-apiofuranosyl(1-->6)-beta-D-glucopyranoside, along with eight known compounds were isolated from the roots of Symplocos caudata Wall. Their structures were elucidated by spectroscopic and chemical methods.

Phenolic compounds obtained from stems ofcouepia ulei with the potential to induce quinone reductase

Activity-guided fractionation of the EtOAc-soluble extract of the stems of Couepia ulei, using a bioassay based on the induction of quinone reductase (QR) in cultured Hepa 1c1c7 mouse hepatoma cells led to the isolation of two active compounds, a new natural product, erythro-2,3-bis(4-hydroxy-3-methoxyphenyl)-3-ethoxypropan-1-ol (1), and a known compound, evofolin-B (2), along with five inactive compounds all of known structure, viz., betulinic acid, oleanolic acid, pomolic acid, (+/-)-syringaresinol, and ursolic acid. These isolates were identified by analysis of physical and spectral data. Compounds 1 and 2 exhibited QR inducing activity, with observed CD (concentration required to double induction) values of 16.7 and 16.4 microM, respectively.