Two new aryl naphthalide lignans from Polygala chinensis

Chinensinaphthol and chinensinaphihol methyl ether, two new 1-ary]-2,3-naphthalide lignans, have been isolated from the title plant. Structures (2) and (3) have been established for them by chemical transformations and spectral evidence. Significant quantitative variations in the content of the cyclic and the acyclic lactonic lignans (1–3, 5–7) of P. chinensis have been observed in plant material, collected from the same locality and examined in 3 consecutive years.     

Isolation,structure elucidation and in-vitro evaluation of new trisubstituted Tetrahydrofuran Lignans from Rabdosia lophanthoides var. gerardiana as anti-inflammatory agents

Four new trisubstituted tetrahydrofuran lignans, named (−)-sesaminone-rutinoside (1), (+)-episesaminone-rutinoside (2) and rabdosiacosides B (3) and C (4) were isolated from the air-dried whole herbs of Rabdosia lophanthoides var. gerardiana together with two known compounds, (+)− 1-hydroxypinoresinol-1-β-d-glucoside (5) and rosmarinic acid (6). The structures of these new lignans were elucidated by a combination of mass spectrometry, 1D and 2D NMR experiments including distortionless enhancement by polarization transfer, ¹H–¹H correlation, heteronuclear single quantum coherence, heteronuclear multiple bond correlation, and nuclear Overhauser effect spectroscopies. Both the cell viability and their anti-inflammatory effects of the lignans were further studied. Among them, no significant cytotoxic activity was exhibited. Compound 4 dramatically suppressed LPS-induced nitric oxide release and reduced the release of the pro-inflammatory cytokines TNF-α and IL-6 in a dose-dependent manner. Overall, our findings indicate that compound 4 was noteworthy in reducing LPS-induced inflammatory responses in RAW264.7 macrophages.     

Chemical constituents from Ailanthus altissima (Mill.) Swingle and chemotaxonomic significance

Sixteen compounds were isolated from the root barks of Ailanthus altissima (Mill.) Swingle, including thirteen lignans (1–13), two coumarins (14–15), and one chalcone (16). This is the first report on the occurrence of compounds 1–16 in the genus Ailanthus. Their structures were elucidated on the basis of NMR spectroscopic data. The plant distribution network of all isolated compounds was described to illustrate the significance of taxonomy. The presence of these congenetic lignans (1–13) and their biosynthetic relationships may be used for identification of Ailanthus genus.     

Lignans from the fruit of Schisandra sphenanthera,and their inhibition of HSV-2 and adenovirus

The systematic isolation of the EtOAc extract from Schisandra sphenanthera fruit was performed during a search for HSV-2 and adenovirus inhibitors. Sixteen lignans were obtained, with compound 1 representing a new and rare type of lignan in the genus Schisandra. Their structures were elucidated by spectroscopy and comparison with literature data. Among all the lignans tested for their antiviral activities, compound 14 was the most active against HSV-2 with a selectivity index value up to 29.83. Moreover, the new compound 1, and the known ones (4, 6, 7, 10 and 14) also exhibited moderate inhibition of HSV-2 and adenovirus. To the best of our knowledge, this is the first report that these lignans from Schisandra genus were shown to have modest activity against HSV-2 and adenovirus. Meanwhile, structure–activity relationships of some lignans for the inhibitory activity against HSV-2 and adenovirus were discussed in this study.     

Three new iridoid glycosides isolated from the traditional herb Siphonostegia chinensis with NF-κB inhibitory activity

Siphonoids A–C (1–3), among which siphonoids A-B (1–2) are rare (E)-p-coumaroyl iridoids, were isolated from Siphonostegia chinensis along with ten known iridoids (4–13) and four lignans (14–17). The structures of the compounds were established by 1D- and 2D-NMR spectroscopy and mass spectrometry. Most of the iridoids isolated from S. chinensis were found to possess (E)-p-coumaroyl iridoid subtype skeletons. Hence, this type of iridoid could be regarded as a chemotaxonomic marker of S. chinensis. The inhibition activities for the NF-κB pathway of iridoids (1–6) were detected. The present results showed that compounds 1–2 and 4–6 processed moderate activity towards the inhibition of NF-κB.     

Chemical constituents from the stems of Tripterygium regelii

Phytochemical investigation on the stems of Tripterygium regelii resulted in the isolation of fourteen compounds, including six flavonoids (1–6), seven lignans (7–13), and one cyanogenic glycoside (14). This is the first report of the four dimeric flavonoids bis-8, 8′-catechinylmethane (2), bis (8-epicatechinyl) methane (3), bis-6, 8′-catechinylmethane (4) and montahomobisflavan B (5) from a species of Tripterygium. Previously, these dimeric flavonoids have been mainly identified from species of gymnosperms. This research has shown that the main secondary metabolisms identified in T. regelii were flavonoids and lignans. These data enable this species to be differentiated from T. wilfordii and T. hypoglaucum that contain the triptolide-resembling diterpenoids.     

Anti-hepatitis B virus lignans from the root of Streblus asper

Four new lignans, strebluslignanol F (1), (7′R,8′S,7″R,8″S)-erythro-strebluslignanol G (2), isomagnaldehyde (3) and isostrebluslignanaldehyde (4), along with 12 known lignans (5–16) were isolated from the ethyl acetate-soluble part of MeOH extract of the root of Streblus asper. Their structures were elucidated through various spectroscopic methods, including 1D NMR (¹H NMR, ¹³C NMR), 2D NMR (HMQC, HMBC and NOESY) and HRMS. The stereochemistry at the chiral centers was determined using CD spectra, as well as analyses of coupling constants and optical rotation data. The isolated lignans were evaluated for their anti-HBV activities in vitro using the HBV transfected HepG2.2.15 cell line. The most active lignans, (7′R,8′S,7″R,8″S)-erythro-strebluslignanol G, magnolol, isomagnolol and isolariciresinol, exhibited significant anti-HBV activities with IC₅₀ values of 1.58, 2.03, 10.34 and 3.67 μM, respectively, for HBsAg with no cytotoxicity, and of 3.24, 3.76, 8.83 and 14.67 μM, respectively, for HBeAg with no cytotoxicity. (7′R,8′S,7″R,8″S)-erythro-Strebluslignanol G and magnolol showed significant anti-HBV activities to inhibit the replication of HBV DNA with the IC₅₀ values of 9.02 and 8.67 μM, respectively.     

Antimicrobial lignans derived from the roots of Streblus asper

Four new lignans, (7′R,8′S)-4,4'-Dimethoxy-strebluslignanol (1), 3'-Hydroxy-isostrebluslignaldehyde (2), 3,3'-Methylene-bis(4-hydroxybenzaldehyde) (3), and 4-Methoxy-isomagnaldehyde (4), and six known lignans (5–10), were isolated from the roots of Streblus asper. The structures of these molecules were elucidated through various spectroscopic methods of analysis, including 1D and 2D NMR. The stereochemistry at the chiral centres was determined using the CD spectrum and from coupling constant and optical rotation data. Compounds 1–6 showed good antimicrobial activity against Saccharomyces cerevisiae (ATCC 9763), Bacillus subtilis (ATCC 6633), Pseudomonas aeruginosa (ATCC 9027), Escherichia coli (ATCC 11775), and Staphylococcus aureus (ATCC 25923), with MIC values ranging from 0.0150 to 0.0940 μM.     

A new pyrrolizidine alkaloid and other constituents from the roots of Ligularia achyrotricha (Diels) Ling

Ligularia achyrotricha (Diels) Ling has been used as a traditional Tibetan herbal medicine. Ligulachyroine A (1), a new twelve-membered macrocyclic pyrrolizidine alkaloid with a ketonic group located at C-3 and an hydroxy group linked at C-8, was isolated from the roots of L. achyrotricha. It is particularly noteworthy that the structure of 1 rarely appears in any other naturally occurring twelve-membered macrocyclic pyrrolizidine alkaloid reported to date. Three known lignans (2–4) and eight known coniferyl and sinapyl alcohol derivatives (5–12) were also obtained in this species. Their structures were elucidated through a careful analysis of their IR, MS, and NMR spectra. Compound 1 exhibited moderate activity against HL-60 and SMMC-7721 cells.     

Chemical constituents from Chonemorpha griffithii

Chemical investigation of the aerial part of Chonemorpha griffithii has led to the isolation of 20 compounds, comprising six lignans (1–6), six triterpenoids (7–12), four phenolic acids (13–16), two flavonoids (17 and 18), one cyclitol (19) and one aliphatic acid (20). Among them, 5′-methoxy-7′-oxomatairesinol (1) was identified to be a new lignan. It is the first report of the presence of those compounds in this genus. Two 24-methyl-29-norcycloartane triterpenoids (10 and 11) were considered as the chemotaxonomic markers for the species C. griffithii.     

Chemical constituents from the roots of Zizyphus jujuba Mill. var. spinosa

One new flavonoid, named (R)-2-hydroxynaringenin (1), along with fifteen known compounds, including six flavonoids (2–7), six lignans (8–13), two phenolic glycosides (14–15) and one alkaloid (16) were isolated from the roots of Zizyphus jujuba Mill. var. spinosa (Bunge) Hu ex H. F. Chou. Their structures were established on the basis of spectroscopic evidence, including 1D and 2D NMR, circular dichroism (CD) curve analysis, and by comparison with literature data. Compounds 2, 3 and 8–16 were found in Z. jujuba Mill. var. spinosa for the first time, while compounds 8, 10 and 13–15 were new to the Rhamnaceae family. In addition, the chemotaxonomic significance of the isolates was discussed in this paper.     

Chemical study of Anthospermum emirnense (Rubiaceae)

Chemical study of the aerial parts of Anthospermum emirnense led to the isolation of one original iridoid glycoside (1) along with six known iridoids (2–7), three lignans (8–10), two flavonoids (11–12), one coumarin (13), two anthraquinones (14–15), two benzoic acids (16–17) and three triterpenoids (18–20). These results are the first chemical data on non-volatile constituents of this genus. The chemotaxonomic significance of these compounds is discussed.     

Chemical constituents isolated from Valeriana officinalis L

Phytochemical investigations on the leaves of Valeriana officinalis L. led to the isolation of 18 compounds, including eight lignans (1–8), three sesquiterpenoids (9–11), five iridoids (12–16), and two aldehydes (17–18) The structure elucidation of isolated compounds was achieved on the basis of NMR and mass spectral data. Among them, three compounds (9–16, 18) are reported from V. officinalis for the first time and one compound (5) was isolated from the genus Valeriana for the first time. In addition, six compounds (2, 4, 6–8, 17) are isolated for the first time from Valerianaceae family. The chemotaxonomic significance of these isolated compounds has also been discussed.     

Chemical constituents of Peperomia tetraphylla (Forst. F.) Hooker et Arnott

Sixteen compounds were isolated from the whole herbs of Peperomia tetraphylla (Forst. F.) Hooker et Arnott by phytochemical methods, including eight flavonoids (1–3, 6, 7, 14–16), three lignans (8–10), three beta sitosterols (4, 5, 11), and two phenolic acids (12, 13). Their structures were identified by the analysis of NMR and MS, as well as the comparisons to the reported data. Among them, 2″-O-xylosylisoswertisin (14) was firstly isolated from the Piperaceae family, as well as ten compounds (1–4, 7, 10–11, 13, 15–16) were isolated from P. tytraphylla for the first time. Moreover, the chemotaxonomic significance of constituents isolated from P. tytraphylla was also discussed.     

Phytochemical and chemotaxonomic studies on Phyllodium pulchellum (Leguminosae)

A phytochemical investigation on the aerial part of Phyllodium pulchellum led to the isolation of 16 compounds including five flavonoids (1–5), three lignans (6–8), four indole alkaloids (9–12), and four other-type compounds (13–16). Their structures were elucidated by their spectroscopic data analysis. Among them, 12 compounds (1, 2, 4–9, and 11–14) are reported from the genus Phyllodium for the first time, while compound 14 was isolated from the Leguminosae family for the first time and compound 11 was firstly reported in the plant kingdom. The chemotaxonomic significance of these compounds was also summarized.     

Phenylpropanoids and some nitrogen-containing constituents from the roots of Isatis indigotica Fort. (Cruciferae)

The present phytochemical investigations of Isatis indigotica Fort. resulted in the isolation of seven lignans (1–7), three aromatic glycosides (8–10), three nucleosides (11–13) and two bis-indole alkaloids (14–15). Among them, compounds 5, 6 and 9 were obtained from this genus for the first time. The chemotaxonomic importance of these compounds was also summarized.     

Chemical constituents from Anemone vitifolia Buch.-Ham. (Ranunculaceae)

A phytochemical investigation of Anemone vitifolia (Buch.-Ham.) led to the isolation of twelve compounds, including six lignans (1–6), four benzoic acid esters (7–10), one norsesquiterpenoid (11) and one lactone (12). The structures of these metabolites were established on the basis of detailed spectroscopic analysis, as well as comparisons with the data available in the literature. Among them, compounds 10 (dimethyl 2-(benzoyloxy)succinate) and 12 (4-hydroxy-5-methyl-γ-butyrolactone) were isolated for the first time as natural products. Compounds 1 and 11, compounds 2, 3, 5–7 and 9, and compounds 4 and 8 were isolated for the first time in family Ranunculaceae, genus Anemone and A. vitifolia respectively. The chemotaxonomic significance of the isolated compounds was discussed.     

Anti-liver fibrotic lignans from the fruits of Schisandra arisanensis and Schisandra sphenanthera

Three new polyoxygenated C₁₈-dibenzocyclooctadiene lignans, arisanschinins M and N (1 and 2) and schisphenin A (3), together with eight related metabolites (4–11), were isolated from the fruits of Schisandra arisanensis and Schisandra sphenanthera, respectively. The structures of 1–3 were elucidated on the basis of extensive spectroscopic and 2D NMR (HSQC, HMBC, and NOESY) analyses. The configuration of the biphenyl moiety in the octadiene ring was determined by circular dichroism (CD). Compound 1 possessed an unprecedented 3-(1-hydroxypropan-2-yl)-3-methyl-1,4-dioxo-2-one lactonide ring system attaching at C-6/C-14. Pharmacological studies revealed that compounds 3, 4, 6, 7, and 10 exhibited significant anti-hepatic fibrosis activity, while 9 and 11 showed cytotoxicity against HSC-T6 cells. The biogenetic pathway for compound 1 was also proposed.     

Sortase A inhibitory metabolites from the roots of Pulsatilla koreana

Three new lignans (3, 4, and 6) along with eight known lignans and phenyl propanoids were isolated from the dried roots of Pulsatilla koreana, an oriental folk medicine. Based upon the results of combined spectroscopic and chemical methods, the structures of new compounds were determined to be lignan glycosides. Included among the known compounds are three compounds (5, 7, and 8) isolated first time from this plant as well as two compounds (2 and 11) previously reported only as synthetic derivatives. These compounds significantly inhibited the action of Sortase A from Streptococcus mutans OMZ65, an isolate from human oral cavity.     

Phenylpropanoids and lignans from Prunus tomentosa seeds as efficient β-amyloid (Aβ) aggregation inhibitors

Alzheimer’s disease (AD) is characterized by the progressive accumulation of extracellular β-amyloid (Aβ) aggregates. Recently, lignans and phenylpropanoids are attracting increasing attention to discovery useful agents of inhibition on Aβ aggregation. In the present study, to develop potential agents for slowing the progression of AD, Prunus tomentosa seeds were selected as a raw material for bioactive compounds, which led to the separation of two pairs of new enantiomeric lignans and phenylpropanoids using chiral HPLC. The planar structures of these compounds were elucidated by spectroscopic data analyses. And their absolute configurations were determined by comparing of experimental and calculated electronic circular dichroism (ECD). The biosynthesis pathway was also discussed. Additionally, the inhibitory activity on Aβ aggregation of all optical pure compounds was tested by thioflavin T (ThT) assay. The isolates (1a, 1b, 2a and 2b) showed more potent inhibitory activity than positive control curcumin with inhibitory rate of 73.89 ± 3.41% 78.69 ± 1.50%, 63.25 ± 2.68%, and 67.13 ± 0.90% at 20 μM, respectively. More importantly, the inhibition profiles were explained by molecular dynamics and docking simulation studies.