Bioactive lignans from Peperomia duclouxii

A Comprehensive Study to Unleash the Putative Inhibitors of Serotype2 of Dengue Virus: Insights from an In Silico Structure-Based Drug Discovery

Dengue fever is a mosquito-borne disease that claims the lives of millions of people around the world. A number of factors like disease's non-specific symptoms, increased viral mutation, growing antiviral drug resistance due to reduced susceptibility, unavailability of an effective vaccine for dengue, weak immunity against the virus, and many more are involved. Dengue belongs to the Flaviviridae family of viruses. The two species of the vector transmitting dengue are Aedes aegypti and Aedes albopictus, with the former one being dominant. Serotypes 2 of dengue fever are spread to the human body and cause severe illness. Recently, dengue has imposed an aggressive effect synergistically with the COVID-19 pandemic. As a result, we concentrated our efforts on finding a potential therapeutic. For this, we chose natural compounds to fight dengue fever, which is currently regarded as successful among many drug therapies. Following this, we started the in silico experiment with 922 plant extracts as lead compounds to fight serotype 2. In this study, we used SwissADME for analyzing ligand drug-likeness, pkCSM for designing an ADMET profile, Autodock vina 4.2 and Swissdock tools for molecular docking, and finally Desmond for molecular dynamics simulation. Ultimately 45 were found effective against the 2'O methyltransferase protein of serotype 2. CHEMBL376820 was found as possible therapeutic candidates for inhibiting methyltransferase protein in this thorough analysis. Nevertheless, more in vitro and in vivo research are required to substantiate their potential therapeutic efficacy.

New Anti-Glycative Lignans from the Defatted Seeds of Sesamum indicum

Seven known analogs, along with two previously undescribed lignan derivatives sesamlignans A (1) and B (2), were isolated from a water-soluble extract of the defatted sesame seeds (Sesamum indicum L.) by applying the chromatographic separation method. Structures of compounds 1 and 2 were elucidated based on extensive interpretation of 1D, 2D NMR, and HRFABMS spectroscopic data. The absolute configurations were established by analyzing the optical rotation and circular dichroism (CD) spectrum. Inhibitory effects against the formation of advanced glycation end products (AGEs) and peroxynitrite (ONOO^-) scavenging assays were performed to evaluate the anti-glycation effects of all isolated compounds. Among the isolated compounds, (1) and (2) showed potent inhibition towards AGEs formation, with IC₅₀ values of 7.5 ± 0.3 and 9.8 ± 0.5 μM, respectively. Furthermore, the new aryltetralin-type lignan 1 exhibited the most potent activity when tested in the in vitro ONOO^- scavenging assay.

Norbisabolane-type sesquiterpenoid derivatives, benzofuran lignans and a phenolic glycoside from the roots of Glochidion wilsonii Hutch

Three highly oxygenated norbisabolane sesquiterpenoid glycosides (glochiwilsonosides A-C), five benzofuran lignans (glochiwilsonises A-E) and a phenolic glycoside (glochiwilsophe-noside), together with forty-one known compounds, were isolated from the roots of Glochidion wilsonii Hutch. The chemical structures of the compounds were identified by spectroscopic methods and previous literature data. Glochiwilsonoside A displayed anti-proliferative activity on A-549 and RAW 264.7 cell lines with an IC50 value of 34.5 ± 0.9 μM and CC50 value of 16.0 ± 0.9 μM, respectively. Twenty-three known compounds were reported from the genus Glochidion for the first time, and the chemotaxonomic characteristics of the isolated compounds were also summarized. The bisabolane/norbisabolane-type sesqui-terpenoid derivatives could be used as chemotaxonomic markers for G. wilsonii.

Design, Synthesis and Evaluation of Novel 1,4-Disubstituted Piperazine-2,5-dione Derivatives as Antioxidants against H2O2-Induced Oxidative Injury via the IL-6/Nrf2 Loop Pathway

Excessive reactive oxygen species (ROS) production leads to oxidative stress in cells, impairing the function of mitochondria and finally inducing cell apoptosis. Considering the essential role of oxidative stress in the pathogenesis of various neurodegenerative diseases and psychiatric disorders, the discovery of novel antioxidants has attracted increasing attention. Herein, a series of novel 1,4-disubstituted piperazine-2,5-dione derivatives were designed, synthesized and evaluated for their antioxidative activity. The results of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay indicated that none of the tested compounds showed significant toxicity to SH-SY5Y cells at concentrations up to 80 μM. Cell counting via flow cytometry revealed that most of the tested compounds could effectively protect SH-SY5Y cells from H₂O₂-induced oxidative damage at 20 μM. Among these compounds, compound 9r exhibited the best antioxidative activity. Further mechanistic investigation indicated that 9r decreased ROS production and stabilized the mitochondrial membrane potential to restrain cell apoptosis, and promoted cell survival via an IL-6/Nrf2 positive-feedback loop. These results suggested the potential of compound 9r as a novel antioxidative candidate for the treatment of diseases caused by oxidative stress.

Natural Bioactive Cinnamoyltyramine Alkylamides and Co-Metabolites

Natural products are a vital source for agriculture, medicine, cosmetic and other fields. Among them alkylamides are a broad and expanding group found in at least 33 plant families. Frequently, they possess a simple carbon skeleton architecture but show broad structural variability and important properties such as immunomodulatory, antimicrobial, antiviral, larvicidal, insecticidal and antioxidant properties, amongst others. Despite to these several and promising biological activities, up to today, only two reviews have been published on natural alkylamides. One focuses on their potential pharmacology application and their distribution in the plant kingdom and the other one on the bioactive alkylamides specifically found in Annona spp. The present review is focused on the plant bioactive cinnamoyltyramine alkylamides, which are subject of several works reported in the literature. Furthermore, the co-metabolites isolated from the same natural sources and their biological activities are also reported.

A new skeleton flavonoid and a new lignan from Portulaca oleracea L. and their activities

A new skeleton flavonoid, identified as (5aR)-10-hydroxy-8-methoxy-5aH,11H-chromeno[2,3-b]chromen-11-one (1), named oleracone G, and a new lignan, confirmed as 8-(4-hydroxy-3-methoxyphenyl)-3-methoxynaphthalen-2-ol (2), named oleralignan B, were isolated from Portulaca oleracea L., and the structures of them were determined using spectroscopic methods including UV, IR, 1D NMR, 2D NMR, and UHPLC-ESI-QTOF/MS. In addition, compounds 1-2 were applied to investigate the anti-inflammatory activities on lipopolysaccharide-stimulated macrophages and scavenging effects in 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical. The results showed that the two compounds at 10 μM and 20 μM could dose-dependently decrease the secretion of interleukin 1β in RAW 264.7 cells by enzyme-linked immunosorbent assay, moreover, presented remarkable antioxidant activities with IC₅₀ values of 27.57, 20.12 μM, respectively.

Chemical Constituents from the Roots and Rhizomes of Asarum heterotropoides var. mandshuricum and the In Vitro Anti-Inflammatory Activity

Anti-inflammatory compounds were investigated from the ethanol extract of the roots and rhizomes of Asarum heterotropoides var. mandshuricum, a traditional Chinese medicine called Xixin and used for pain and inflammatory. Nine new compounds were isolated, including six new lignans, neoasarinin A–C (1–3), neoasarininoside A and B (4 and 5), and asarinin B (7), and one new monoterpene, asarincin A (8), two new amides, asaramid II and III (10 and 11), and one new natural monoterpene, asaricin B (9), along with 37 known compounds (6, 12–47). Their structures and absolute configurations were elucidated on the basis of spectroscopic methods and chemical analyses. This is the first report of the absolute configuration of asarinin A (6). The 8-O-4′ neolignans (1–5) were reported in the genus Asarum for the first time. The 15 compounds 17, 19, 22–25, 28, 31, 36, 40, 42, 43, 45–47 were isolated from the genus Asarum, and compounds 16, 32, 33, 37 and 39 were isolated from A. heterotropoides var. mandshuricum for the first time. Thirty-seven of the isolates were evaluated for anti-inflammatory activity against the release of β-glucuronidase in polymorphonuclear leukocytes (PMNs) induced by the platelet-activating factor (PAF), and compounds 1, 4, 7, 8, 14, 17–19, 22, 24, 25, 29, 30, 32, 33, 40–43, 45, and 46 showed potent anti-inflammatory activities in vitro, with 27.9%–72.6% inhibitions at 10⁻⁵ mol/L. The results of anti-inflammatory assay suggested that lignans obtained from the CHCl₃ extract might be the main active components of Xixin.

Peperotetraphin inhibits the proliferation of human prostate cancer cells via induction of cell cycle arrest and apoptosis

Peperotetraphin (methyl rel-(1R,2S,3S)-2,3-bis(7-methoxy-1,3-benzodioxol-5-yl) cyclobutanecarboxylate) was a novel cyclobutane-type norlignan, which was isolated from the whole plant of Peperomia tetraphylla. In this study, we explored its anti-tumor effect and the molecular mechanism in human prostate cancer PC-3 cell lines. Firstly, cell viability was evaluated by Cell Counting Kit (CCK-8) assay. The PC-3 cells were treated with increasing concentrations of peperotetraphin for 24, 48 and 72 h, respectively. The results showed that peperotetraphin inhibited the growth of PC-3 cell in a dose- and time-dependent manner. Next, the cell cycle distributions were analyzed by flow cytometric analysis (FCM), and the data suggested that peperotetraphin could significantly induce cell cycle arrested at the G1-S phase transition. Then, the cell apoptosis was detected by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and annexin V-FITC/PI dual staining analysis, the data confirmed apoptosis-inducing activity of peperotetraphin and the apoptosis rates increased from 3.9 to 32.3 % when treated with increasing concentrations of peperotetraphin from 0 to 50 µM. The expression levels of apoptosis-regulating protein caspase-3, Bax and Bcl-2 were also analyzed by Western blot analysis. The results showed that the expression levels of Bax and the activity of caspase-3 were upregulated, whereas the expression levels of Bcl-2 were downregulated compared with those of the control. These findings demonstrated that peperotetraphin exhibited effective cell growth inhibition by inducing cancer to undergo G1 phase arrest and apoptosis. The results suggested that peperotetraphin might have potential as chemoprevention or anti-tumor agent to prostatic cancer.

New lignans and their biological activities

Lignans, which are widely distributed in higher plants, represent a vast and rather diverse group of phenylpropane derivatives. They have attracted considerable attention due to their pharmacological activities. Some of the lignans have been developed approved therapeutics, and others are considered as lead structures for new drugs. This article is based on our previous review of lignans discovered in the period 2000-2004, and it provides a comprehensive compilation of the 354 new naturally occurring lignans obtained from 61 plant families between 2005 and 2011. We classified five main types according to their structural features, and provided the details of their sources, some typical structures, and diverse biological activities. A tabular compilation of the novel lignans by species is presented at the end. A total of 144 references were considered for this review.

A new sesquilignan glucoside from Uraria sinensis

A new sesquilignan glucoside, urariasinoside A (1), together with eight known compounds, including two lignans, a sesquilignan, a dilignan, and four flavonoid derivatives were isolated from the aerial parts of Uraria sinensis. Their structures were determined on the basis of extensive spectroscopic analyses and comparison with literature data. Compound 1 was evaluated for in vitro cytotoxicity activity against HL-60, SMMC-7721, A549, MCF-7, SW480, and BEAS-2B cell lines.

Natural aristolactams and aporphine alkaloids as inhibitors of CDK1/cyclin B and DYRK1A

In an effort to find potent inhibitors of the protein kinases DYRK1A and CDK1/Cyclin B, a systematic in vitro evaluation of 2,500 plant extracts from New Caledonia and French Guyana was performed. Some extracts were found to strongly inhibit the activity of these kinases. Four aristolactams and one lignan were purified from the ethyl acetate extracts of Oxandra asbeckii and Goniothalamus dumontetii, and eleven aporphine alkaloids were isolated from the alkaloid extracts of Siparuna pachyantha, S. decipiens, S. guianensis and S. poeppigii. Among these compounds, velutinam, aristolactam AIIIA and medioresinol showed submicromolar IC50 values on DYRK1A.

Two New Norlignans and a New Lignanamide from Peperomia tetraphylla

Two new cyclobutane-type norlignans, methyl rel-(1R,2S,3S)-2-(7-methoxy-1,3-benzodioxol-5-yl)-3-(2,4,5-trimethoxyphenyl)cyclobutanecarboxylate (1), and methyl rel-(1R,2R,3S)-2-(7-methoxy-1,3-benzodioxol-5-yl)-3-(2,4,5-trimethoxyphenyl)cyclobutanecarboxylate (2), and a new lignanamide, 3-hydroxy-N-[2-(4-hydroxyphenyl)ethyl]-α-[4-(2-{N-[2-(4-hydroxyphenyl)ethyl]carbamoyl}ethenyl)-3-methoxyphenoxy]-4-methoxycinnamamide 4,8″-ether (3), along with five known amides, 4-8, were obtained from the whole plant of Peperomia tetraphylla. Their structures were elucidated mainly by the analysis of NMR and MS data. The new compounds 1-3 and the known compound 4 were tested for their cytotoxic activities against the HepG2 (human hepatocarcinoma), A549 (human lung cancer), and HeLa (human cervical cancer) cell lines. Compound 4 showed significant cytotoxicity against HepG2 cell lines with an IC(50) value of 9.4 ± 1.0 μM.

Bioactive neolignans and lignans from the bark of Machilus robusta

Sixteen new neolignans and lignans (1-16), together with 12 known analogues, have been isolated from an ethanol extract of the bark of Machilus robusta. Compounds 1 and 2 showed activity against HIV-1 replication in vitro, with IC(50) values of 2.52 and 2.01 μM, respectively. At 10 μM, 6, 8, and 9 reduced dl-galactosamine-induced hepatocyte (WB-F344 cells) damage, and 9 could additionally attenuate rotenone-induced PC12 cell damage. The known compounds (-)-pinoresinol (17) and (+)-lyoniresinol (18) were active against serum deprivation induced PC12 cell damage.

Synthesis and antioxidant capacities of hydroxyl derivatives of cinnamoylphenethylamine in protecting DNA and scavenging radicals

Cinnamoylphenethylamine (CNPA) derivatives including feruloylphenethylamine (FRPA), caffeoylphenethylamine (CFPA), cinnamoyltyramine (CNTA), feruloyltyramine (FRTA) and caffeoyltyramine (CFTA) were synthesized in order to investigate the influence of the number and position of hydroxyl group on Cu(2+)/glutathione (GSH) and 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced oxidation of DNA. The radical-scavenging properties of these CNPA derivatives were also evaluated by trapping 2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonate) cationic radical (ABTS(+•)), 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH) and galvinoxyl radical. In addition, these CNPA derivatives were tested by linoleic acid (LH)-β-carotene-bleaching experiment. The chemical kinetic was employed to treat the results from AAPH-induced oxidation of DNA and gave the order of antioxidant ability as CFTA > CFPA > FRTA > FRPA. CFTA and CFPA also possessed high abilities to inhibit Cu²(+)/GSH-mediated degradation of DNA, whereas FRPA and FRTA can protect LH against the auto-oxidation efficiently. Finally, CFPA and FRPA exhibited high activity in trapping ABTS(+•), DPPH and galvinoxyl radicals. Therefore, the cinnamoyl group bearing ortho-dihydroxyl or hydroxyl with ortho-methoxyl benefited for CNPA derivatives to protect DNA, while hydroxyl in tyramine cannot enhance the radical-scavenging abilities of CNPA derivatives.

New phenanthrenes and stilbenes from Dendrobium loddigesii

New phenanthrenes, loddigesiinols A (1) and B (7), and stilbenes, loddigesiinols C (8) and D (9), were isolated from 80% ethanol extract of Dendrobium loddigesii ROLFE (Orcharedceae) along with known compounds, including five phenanthrenes, three stilbenes, two lignans, and three sterols. Their structures were determined by spectroscopic studies. These compounds were evaluated for their inhibitory activities against nitric oxide (NO) production and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging. Phenanthrenes (1-3, 7) and dihydrophenanthrenes (4-6) showed significant inhibitory activity against NO production. In particular, 2 showed stronger inhibitory activity against NO production than 5 and 6. This suggested that this phenanthrene is a stronger inhibitor of NO production than dihydrophenanthrene. The new phenanthrenes, loddigesiinols A (1) and B (7), significantly inhibited NO production with IC(50) values of 2.6 and 10.9 muM, respectively. One new dihydrostilbene, loddigesiinol D (9), showed weak inhibitory activity against NO production with an IC(50) value of 69.7 microM, but the other new dihydrostilbene, loddigesiinol C (8), did not show this activity at 100 microM.

Synthesis, anti-virus and anti-tumour activities of dibenzylbutyrolactone lignans and their analogues

An efficient synthesis of dibenzylbutyrolactone lignans and their analogues has been developed. Based on a Stobbe condensation of piperonal or veratraldehyde with diethylsuccinate and alkylation with 3,4-methylenedioxybenzyl bromide to give the skeleton of the lignan. The (±)-diacid was resolved with quinine and the functional groups were transformed to obtain three benzylbutyrolactone lignans and seven analogues. Four natural lignans were prepared by this method, and five lignans were synthesised for the first time. The synthesised compounds were evaluated for anti-HIV, anti-HSV, and anti-tumour activities. Results showed that the dibenzylbutyrolactone lignans and their analogues were inactive against HIV Tat transactivation and HSV-1 in vitro, but some compounds displayed significant activity against MDA-MB-435 human breast cancer cell.

A new furofuran lignan from Isodon japonicus

A new sesamin type furofuran lignan, (-)-sesamin-2,2'-diol (1), along with two known flavonoids (2 and 3) and three phenolic compounds (4-6) were isolated from the aerial parts of Isodon japonicus. The structures of these compounds were determined by analysis of spectroscopic data (1D-, 2D-NMR, HRMS and CD) and by comparison of the data with those of related metabolites.

C-glycosyl flavones from Peperomia blanda

The methanol extract from aerial parts of the Peperomia blanda (Piperaceae) yielded two C-glycosyl-flavones. Their structures were elucidated on the basis of extensive spectroscopic analysis, including 1D and 2D NMR, chemical transformation and comparison with the related known compounds. The structure of the new flavonoids were established as 4'-methoxy-vitexin 7-O-beta-D-xylopyranoside (1) (7-O-beta-D-xylopyranosyl-8-C-beta-D-glucopyranosyl-4'-methoxy-apigenin) and vicenin-2 (2). The antioxidant activity of both compounds was investigated using the DPPH assay. Both compounds showed only modest activity, with IC50 values of 357.2 microM for 1, and 90.5 microM for 2.

Trypanocidal tetrahydrofuran lignans from Peperomia blanda

Five tetrahydrofuran lignans and two known flavones were isolated from the aerial parts of Peperomia blanda. The structures of the isolated lignans were elucidated by interpretation of their spectroscopic data, including by gHMQC and gHMBC. The relative and absolute configurations of the isolates were determined from NOESY interactions and optical properties, respectively. Four of the lignans were diastereomeric whilst one was of mixed biosynthetic origin. All but one of the lignans exhibited high in vitro trypanocidal activity when assayed against epimastigotes of Trypanosoma cruzi strain Y.