Novel diterpenoids and diterpenoid glycosides from Siegesbeckia orientalis

Kirenol inhibits inflammation challenged by lipopolysaccharide through the AMPK-mTOR-ULK1 autophagy pathway

Kirenol is a bioactive substance isolated from Herba Siegesbeckiae. Although the anti-inflammatory activity of kirenol has been well documented, its role in autophagy remains unknown. The present study aimed to investigate the protective role of kirenol on inflammation challenged by lipopolysaccharide (LPS) in acute lung injury (ALI) cell and mouse models and unravel the underlying mechanisms, with a particular focus on autophagy. For this purpose, an ALI cell and mouse models were established, and the effects of kirenol on the expression of molecules related to inflammation and autophagy were examined. The present results revealed that kirenol could significantly inhibit inflammatory cytokines secretion in cells and in the mice injured by LPS; this effect may be attributed to enhanced autophagy as evidenced by the up-regulation of LC3-II and the down-regulation of p62 both in vitro and in vivo. Phosphorylated AMPK and ULK1 increased, while phosphorylated mTOR decreased in the kirenol-treated ALI cell model. Moreover, inhibition of autophagy using AMPK inhibitor or 3-MA or chloroquine (CQ) reversed the anti-inflammatory and autophagy-enhancement effects of kirenol exposure in vitro, indicating that kirenol could enhance autophagy by activating the AMPK-mTOR-ULK1 pathway. The results of RNA sequencing suggested that kirenol was strongly related to the biological functions of acute inflammatory response and the AMPK signaling pathway. Further in vivo ALI mouse model studies demonstrated the protective role of kirenol against lung inflammation, such as improved histopathology, decreased lung edema, and leukocyte infiltration were abolished by 3-MA. These findings implicate that kirenol can inhibit LPS-induced inflammation via the AMPK-mTOR-ULK1 autophagy pathway.

Kirenol: A promising bioactive metabolite from siegesbeckia species: A detailed review

ETHNOPHARMACOLOGICAL RELEVANCE

Kirenol (Kr) is an ent-pimarane type diterpenoid that has been reported from Siegesbeckiaorientalis, S. pubescens, and S. glabrescens (family Asteraceae). These plants have been used traditionally for treating various ailments such as hypertension, neurasthenia, rheumatoid arthritis, asthma, snakebites, allergic disorders, paralysis, soreness, cutaneous disorders, rubella, menstrual disorders, numbness of limbs, dizziness, headache, and malaria. Importantly, in recent years, Kr has received great attention due to its diversified pharmacological activities.

AIM OF THE STUDY

The current work aims to give an overview on the reported pharmacological activities of Kr. Furthermore, the findings regarding its methods for extraction, quantitative analysis, purification, pharmacokinetics, pharmaceutical and food preparations, biosynthesis, identification, semisynthetic analogues, and toxicity are highlighted to provide a reference and perspective for its further investigation.

METHODS

Electronic databases including ScienceDirect, Web of Knowledge, SCOPUS, Wiley Online Library, Taylor & Francis, PubMed, Springer, JACS, and Google Scholar were searched up to the beginning of 2021 to identify the reported studies.

RESULTS

A total of 93 articles have been reviewed. The reported data suggested that Kr possessed various bioactivities including cytotoxic, apoptotic, anticancer, anti-inflammatory, cardio-protective, anti-photo-aging, anti-adipogenic, antimicrobial, muscle function improvement, fracture and wound healing, and anti-arthritic. In addition, studies revealed that the antioxidative and anti-inflammatory activities of Kr may mediate many of its therapeutic potentials as confirmed by several in-vitro and in-vivo studies.

CONCLUSION

This review provides an updated summary of the recent studies on Kr, including methods for extraction, quantitative analysis, purification, pharmacokinetics, pharmaceutical and food preparations, biosynthesis, and identification, as well as semisynthetic analogues, pharmacological activities, and toxicity. Thus, this work can provide useful considerations for planning and design future research on Kr.

Guaianolide sesquiterpenes and benzoate esters from the aerial parts of Siegesbeckia orientalis L. and their xanthine oxidase inhibitory activity

Five undescribed (four guaianolide sesquiterpenes and a benzoate ester derivative) and seven known compounds were isolated from the aerial parts of S. orientalis L. Their chemical structures were determined by extensive analysis of HR-ESI-MS and NMR spectroscopic methods. Absolute configurations were elucidated by experimental and TD-DFT calculated ECD spectra. Twelve isolated compounds exhibited potential xanthine oxidase inhibitory activity with IC₅₀ values ranging from 0.76 ± 0.17 μM to 31.80 ± 0.97 μM. Molecular docking studies predicted that the binding energies of all isolated compounds with xanthine oxidase were lower than that of the positive control allopurinol. Benzyl 2-hydroxy-6-O-β-D-glucopyranosylbenzoate and benzyl 2-methoxy-6-O-β-D-glucopyranosylbenzoate displayed not only the best docking score but also the highest in vitro xanthine oxidase inhibitory activity with IC₅₀ values of 0.76 ± 0.17 μM and 0.98 ± 0.26 μM, respectively.

Herba Siegesbeckiae: A review on its traditional uses, chemical constituents, pharmacological activities and clinical studies

ETHNOPHARMACOLOGICAL RELEVANCE

Herba Siegesbeckiae, mainly includes Sigesbeckia orientalis L, Sigesbeckiae pubescens Makino and Sigesbeckiae glabrescens Makino. Herba Siegesbeckiae, also known as 'Xi-Xian Cao' (Chinese: ), has been regarded as an important traditional Chinese medicine since Tang dynasty. The dried aerial parts of Herba Siegesbeckiae are also being used as a herbal medicine in many countries such as Japan, Korea and Vietnam. In China, Herba Siegesbeckiae has been used for the treatment of rheumatic arthralgia with aching and weakness of loins and knees, as well as numbness of limbs.

AIM OF THIS REVIEW

The aim of this review was to provide critical analysis on the scientific evidence to support the traditional uses of Herba Siegesbeckiae. The information available on its in botanical characteristics, traditional uses, chemical constituents, pharmacological activities, clinical studies, toxicity and quality control was summarized to understand the current research and provided the leas for future study.

MATERIALS AND METHODS

The search terms "Herba Siegesbeckiae", "Sigesbeckia orientalis", "Sigesbeckia pubscens" and "Sigesbeckia glabrescens" were used to obtain the information from electronic databases such as Web of Science, China National Knowledge Infrastructure, PubMed, Google Scholar and SciFinder Scholar and other web search instruments (Springer, Yahoo search). The information provided in this review was based on peer-reviewed papers in English and Chinese. Besides, information was also collected from ancient documents.

RESULT

The studies showed that Herba Siegesbeckiae contains sesquiterpenoids, diterpenoids, flavonoids and organic acids, etc. Due to these constituents, it displayed numerous pharmacological activities, such as anti-inflammatory, antitumor, antiallergic, antioxidant, antithrombotic and antibacterial activities. In addition, it showed effects in protecting myocardial and cerebral ischemia injury.

CONCLUSIONS

According to its traditional uses, chemical constituents, pharmacological activities and clinic studies, Herba Siegesbeckiae is regarded as a promising medical plant with various chemical compounds and numerous pharmacological activities. However, fewer experimental studies were focused on toxicity and quantitative study of 3 species. It suggested that further in-depth study of toxicity and quality control were critical for future evaluation of drug efficacy and safety.

Shanpanootols A-F, diterpenoids from Kaempferia pulchra rhizomes collected in Myanmar and their Vpr inhibitory activities

Six new isopimarane diterpenoids, shanpanootols A-F (1-6), along with two known analogues, were isolated from the ethyl acetate-soluble extract of Kaempferia pulchra rhizomes collected in Myanmar. The structures of these compounds were elucidated by extensive spectroscopic techniques such as 1D and 2D NMR and HRESIMS. The absolute configuration of 1 was determined by the modified Mosher method. The new isolates (1-6) were tested for their Vpr inhibitory activities against TREx-HeLa-Vpr cells. Shanpanootols C (3) and E (5) inhibited Vpr at doses of 2.5 and 5 μM, respectively.

Protective Effects of Kirenol against Lipopolysaccharide-Induced Acute Lung Injury through the Modulation of the Proinflammatory NFκB Pathway and the AMPK2-/Nrf2-Mediated HO-1/AOE Pathway

Acute lung injury (ALI) is an acute and life-threatening inflammatory disease of the lung parenchyma that is associated with high mortality worldwide. No therapeutic strategies have been developed for the mitigation of the proinflammatory response that characterizes ALI. Kirenol has anti-inflammatory, antiarthritic, and immunoregulatory effects. In the present study, we investigated the protective effects of kirenol against lipopolysaccharides (LPS)-induced ALI in mice. Kirenol reduced the LPS-induced histopathology changes involving edema and thickening of the interstitial or alveolar walls, infiltration of leukocytes, formation of hyaline membrane. Pretreatment with kirenol reduced leukocytes infiltration in bronchoalveolar lavage fluid (BALF), the alveolar-capillary barrier disruption and lipid peroxidation in lung tissues induced by LPS. Kirenol significantly inhibited the secretion of cytokines, IL-1β, IL6, and TNFα, into the BALF of the mice with LPS-induced ALI through NFκB activation. Moreover, kirenol attenuated the downregulation of the antioxidant enzymes, superoxide dismutase, glutathione peroxidase, and catalase that was induced by LPS. HO-1 expression and the phosphorylation of Nrf2 and AMPK2 were also induced by kirenol. The results indicate that kirenol can be developed as a treatment strategy for ALI, and its effects are induced through the inhibition of the NF-κB proinflammatory pathway and promotion of AMPK2/Nrf2-mediated HO-1 and antioxidant enzymes (AOE) activation.

Diverse diterpenoids and sesquiterpenoids from Siegesbeckia pubescens and their activity against RANKL-induced osteoclastogenesis

Phytochemical investigation of the aerial parts of Siegesbeckia pubescens led to seventeen diterpenoids (1-17) and twelve sesquiterpenoids (18-29). Their structures were varied including twelve ent-pimarane (1-12), three ent-kaurane (13-15), two acyclic diterpenoids (16-17), ten germacrene (18-27), one guaiane (28), and one caryolane (29) sesquiterpenoids. Eight of twenty-nine were new ones (1, 3, 4, 16-18, 23, and 28). Their structures were elucidated by extensive spectroscopic analysis. The absolute configurations of compounds 1 and 2 were identified using X-ray diffraction analysis, and of compounds 18, 23, and 28 were elucidated by the experimental and calculated electronic circular dichroism (ECD) spectra. All the isolated compounds (1-29) were assayed for their inhibition of RANKL-induced osteoclastogenesis in bone marrow macrophages (BMMs). Four sesquiterpenoids 18, 25, 26, and 27 exhibited potent inhibition of osteoclastogenesis with IC₅₀ value of 0.51, 0.80, 0.50, and 0.83 μM, respectively. Here we demonstrated that S. pubescens may be a resource for discovery of anti-osteoporosis agents.

Six novel lignanoids with complex structures from Sigesbeckia glabrescens Makino with their cytotoxic activities

Six new lignanoids, Glalignin A-E (1-5) and Glaneolignin A (6), together with four analogues, (+)-isolariciresinol (7), (+)-syringaresinol (8), dihydrodehydrodiconiferyl alcohol (9) and tribulusamide A (10), were obtained from the aerial parts of Sigesbeckia glabrescens Makino and also isolated for the first time from the Sigesbeckia genus. The structures of these compounds were elucidated by the interpretation of HRESIMS, 1D NMR, 2D NMR data and chemical evidence. The cytotoxic activities of the compounds were evaluated by testing their inhibition in several tumor cells using the MTT assay. New compound 2 and 5 displayed cytotoxicity against the human cancer cell lines human lung adenocarcinoma cells (A549) with IC₅₀ values of 32.89 ± 6.83 and 35.86 ± 6.83 μM.

[Kirenol relieves dextran sulfate sodium-induced ulcerative colitis in mice by inhibiting inflammatory cytokines and inducing CD4+ T lymphocyte apoptosis]

OBJECTIVE

To investigate whether kirenol, the major pharmacologically active compound of the Chinese medicinal herb Herba Siegesbeckiae, can protect mice from dextran sulfate sodium (DSS)-induced ulcerative colitis (UC).

METHODS

C57BL/6 mice with or without kirenol pretreatment were treated with DSS in drinking water for 7 days to induce UC. The symptoms of UC including weight loss, diarrhea and bloody stool were observed daily and graded using the disease activity index (DAI). Colon injury of the mice was assessed by measuring the length of the colon and HE staining of the colon tissue. The levels of inflammatory cytokines produced by the mesenteric lymph nodes (MLNs) lymphocytes were measured using enzyme-linked immunosorbent assay; the apoptosis of the lymphocytes and CD4⁺ T cells was analyzed using flow cytometry.

RESULTS

The mice receiving pretreatment with kirenol showed obviously ameliorated symptoms of UC and milder pathological changes in the colon as compared with the control mice. Kirenol treatment significantly down-regulated the secretion of IFN-γ, IL-17A, IL-6 and TNF-α by the MLNs lymphocytes and increased the apoptosis of lymphocytes, especially CD4⁺ T cells in the DSS-treated mice.

CONCLUSIONS

Kirenol can protect against T cell-mediated colon injury in DSS-treated mice possibly by suppressing the secretion of inflammatory mediators and inducing apoptosis of the inflammatory lymphocytes.

A selection of eleven plants used as traditional Polynesian cosmetics and their development potential as anti-aging ingredients, hair growth promoters and whitening products

ETHNOPHARMACOLOGICAL RELEVANCE

In French Polynesia, embellishment of the hair and skin is an important cultural and everyday practice. Yet, little research has focused on traditional preparations used for beautification in this region and their potential development as innovative cosmetic ingredients.

AIM OF THE STUDY

In this present study we aim to assess and compile the ethnocosmetic potential of plants of French Polynesia to select and further study plants showing the most promise to be developed as anti-aging, anti-blemish and hair care products.

MATERIALS AND METHODS

A literature analysis of plants of the IECIC list, present in French Polynesia was conducted. The most interesting plants from a cosmetic development standpoint were selected based on four main criteria, i.e. their traditional use in Polynesian cosmetic-related preparations, their biogeographical status, their phytochemistry of cosmetic interest, and lastly their availability and absence from the UICN list. Furthermore, a preliminary screening of antioxidant and anti-inflammatory activities was also performed on several extracts obtained.

RESULTS

Eleven plants were chosen, and a compilation of multidisciplinary data emphasized each selected plant's potentiality. Traditional allegations showed uses ranging from dermatology such as wound healing or anti-inflammatory properties, to hair growth promoting preparations or even skin ligthening ones. Preliminary screenings were useful in narrowing the number of extracts to study. Literature-based data associated to traditional uses depicted how the remaining plants and plant parts could be developed for targeted cosmetic applications.

CONCLUSIONS

A prospective approach of plants used traditionally for cosmetic purposes in French Polynesia gave insight on their development potential when paired with the appropriate multidisciplinary data. The eleven plants presented show promise in being developed sustainably as natural anti-aging or hair care products and as skin brightening agents.

Comparative Analysis of Chemical Composition, Anti-Inflammatory Activity and Antitumor Activity in Essential Oils from Siegesbeckiaorientalis, S. glabrescens and S. pubescens with an ITS Sequence Analysis

Herba Siegesbeckiae (HS), derived from the aerial parts of three plants, Siegesbeckia orientalis (SO), S. glabrescens (SG), and S. pubescens (SP), has been used for the treatment of inflammatory diseases in China for centuries. In the present study, hydrodistillation was applied to extract essential oils from dried SO, SG, and SP aerial parts, and chemical composition analysis by gas chromatography⁻mass spectrometry (GC-MS) led to the identification of a total of 148 compounds (56 in SO, 62 in SG, and 59 in SP). The main components in the essential oils of SO, SG, and SP differed significantly. In vitro anti-inflammatory activity assays showed that SP essential oils (IC₅₀, 0.97 μg/mL) significantly reduced the ability of lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages to release NO, and the SO essential oil (IC₅₀, 14.99 μg/mL) was better than the others at inhibiting the LPS-induced release of cytokine IL-6. Furthermore, the essential oils exhibited antitumor activities (IC₅₀, 37.72⁻123.16 μg/mL) against Hep3B (liver) and Hela (cervical) cells. Linear regression analysis showed that, caryophyllene oxide peak area percentages showed remarkably high negative correlation coefficients with IC₅₀ values of Hep3B and Hela cytotoxicity, which suggested the contribution of this compound on the cancer cell cytotoxicity of three essential oils. Finally, the ITS1-5.8S-ITS2 region was amplified and sequenced in order to generate genomic reference sequences for each plant. These can be used to identify the origins of the plants, and will assist other research studies related to these three plants.

Site-selective oxidation, amination and epimerization reactions of complex polyols enabled by transfer hydrogenation

Polyoxygenated hydrocarbons that bear one or more hydroxyl groups comprise a large set of natural and synthetic compounds, often with potent biological activity. In synthetic chemistry, alcohols are important precursors to carbonyl groups, which then can be converted into a wide range of oxygen- or nitrogen-based functionality. Therefore, the selective conversion of a single hydroxyl group in natural products into a ketone would enable the selective introduction of unnatural functionality. However, the methods known to convert a simple alcohol, or even an alcohol in a molecule that contains multiple protected functional groups, are not suitable for selective reactions of complex polyol structures. We present a new ruthenium catalyst with a unique efficacy for the selective oxidation of a single hydroxyl group among many in unprotected polyol natural products. This oxidation enables the introduction of nitrogen-based functional groups into such structures that lack nitrogen atoms and enables a selective alcohol epimerization by stepwise or reversible oxidation and reduction.

Anti-Hyperuricemic, Anti-Inflammatory and Analgesic Effects of Siegesbeckia orientalis L. Resulting from the Fraction with High Phenolic Content

Background

The medicinal plant Siegesbeckia orientalis L. has been commonly used for the treatment of acute arthritis, rheumatism, and gout in Vietnam. However, pharmacological research of this plant associated with gout has not been reported. Anti-hyperuricemic and anti-inflammatory effects were evaluated and observed for the crude ethanol extract (CEE) of S. orientalis. Retention of these biological properties was found in a n-butanol-soluble fraction (BuOH fr.) of the extract, and therefore further biological and chemical investigations were undertaken on the BuOH fr. to support the medical relevance of this plant.

Methods

The aerial part of S. orientalis was obtained in the mountainous region of Vietnam. The crude ethanol extract (CEE) and its BuOH fr. were prepared from the plant materials. Anti-hyperuricemic activities of the CEE and BuOH fr. were tested in vivo using the model oxonate-induced hyperuricemia rats through determination of serum uric acid levels and inhibitory effects on xanthine oxidase (XO) in the rat liver. Anti-inflammatory activities of the BuOH fr. were also evaluated in vivo using carrageenan-induced paw edema and urate-induced synovitis in rats. Active components of the BuOH fr. were characterized by comparison of HPLC retention time (t_R) and spectroscopic data (UV, ¹H–NMR) with those of reference compounds.

Results

The CEE of S. orientalis displayed anti-hyperuricemic activity, and the BuOH fr. was found to be the most active portion of the extract. Further in vivo studies on this fraction showed 31.4% decrease of serum uric acid levels, 32.7% inhibition of xanthine oxidase (XO), 30.4% reduction of paw edema volume, symptomatic relief in urate-induced synovitis and significant analgesic effect at the dose of 120 mg/kg, as compared to the corresponding values of the control groups. Chemical analysis of the BuOH fr. revealed high phenolic content, identified as caffeic acid analogues and flavonones.

Conclusions

This study suggested that anti-hyperuricemic and anti-inflammatory mechanism of S. orientalis is related to XO inhibitory effect of the phenolic components. Our findings support the use of this plant as the treatment of gout and other inflammatory diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-017-1698-z) contains supplementary material, which is available to authorized users.

ent-Strobane and ent-Pimarane Diterpenoids from Siegesbeckia pubescens

Two strobane diterpenoids, strobols A (1) and B (2), 15 new pimarane diterpenoids (3-6 and 8-18), and the known compounds kirenol (19), darutigenol (20), and ent-2β,15,16,19-tetrahydroxypimar-8(14)-ene (7) were isolated from the aerial parts of Siegesbeckia pubescens Makino. The structures of the new compounds were established based on the interpretation of HRESIMS and NMR analysis. The configurations of 1, 6, and 17 were confirmed by X-ray crystallographic data. Compounds 3, 5, and 11 inhibited the migration of MB-MDA-231 breast cancer cells induced by the chemokine epithelial growth factor, with IC₅₀ values of 4.26, 3.45, and 9.70 μM, respectively.

Diterpenoids from Leaves of Rubus Chingii

The leaves of Rubus chingii were examined for their phytochemical composition and anti-yeast activity. In the process, seven diterpenoids (compounds 1–7), including a new natural compound (14β, 16-epoxy-7-pimarene-3α, 15β-diol, 1), were isolated and elucidated. Compound 1 exhibited moderate anti- Candida activity.

Kirenol attenuates experimental autoimmune encephalomyelitis by inhibiting differentiation of Th1 and th17 cells and inducing apoptosis of effector T cells

Experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis (MS), is characterized by CNS demyelination mediated by autoreactive T cells. Kirenol, a biologically active substance isolated from Herba Siegesbeckiae, has potent anti-inflammatory activities. Here we investigated effects of kirenol on EAE. Kirenol treatment markedly delayed onset of disease and reduced clinical scores in EAE mice. Kirenol treatment reduced expression of IFN-γ and IL-17A in the serum and proportion of Th1 and Th17 cells in draining lymph nodes. Priming of lymphocytes was reduced and apoptosis of MOG-activated CD4+ T cells was increased in kirenol treated EAE mice. Kirenol treatment of healthy animals did not affect the lymphocytes in these non-immunized mice. Further in vitro studies showed that kirenol inhibited viability of MOG-specific lymphocytes and induced apoptosis of MOG-specific CD4+ T cells in a dose- and time-dependent manner. Kirenol treatment upregulated Bax,downregulated Bcl-2,and increased activation of caspase-3 and release of cytochrome c, indicating that a mitochondrial pathway was involved in kirenol induced apoptosis. Moreover, pretreatment with either a pan-caspase inhibitor z-VAD-fmk or a more specific caspase 3 inhibitor Ac-DEVD-CHO in lymphocytes reduced kirenol induced apoptosis. Our findings implicate kirenol as a useful agent for the treatment of MS.

Kirenol inhibits adipogenesis through activation of the Wnt/β-catenin signaling pathway in 3T3-L1 adipocytes

Kirenol, a natural diterpenoid compound, has been reported to possess anti-oxidant, anti-inflammatory, anti-allergic, and anti-arthritic activities; however, its anti-adipogenic effect remains to be studied. The present study evaluated the effect of kirenol on anti-adipogenesis through the activation of the Wnt/β-catenin signaling pathway. Kirenol prevented intracellular lipid accumulation by down-regulating key adipogenesis transcription factors [peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding proteins α (C/EBPα), and sterol regulatory element binding protein-1c (SREBP-1c)] and lipid biosynthesis-related enzymes [fatty acid synthase (FAS) and acetyl-CoA carboxylase (ACC)], as well as adipocytokines (adiponectin and leptin). Kirenol effectively activated the Wnt/β-catenin signaling pathway, in which kirenol up-regulated the expression of low density lipoprotein receptor related protein 6 (LRP6), disheveled 2 (DVL2), β-catenin, and cyclin D1 (CCND1), while it inactivated glycogen synthase kinase 3β (GSK3β) by increasing its phosphorylation. Kirenol down-regulated the expression levels of PPARγ and C/EBPα, which were up-regulated by siRNA knockdown of β-catenin. Overall, kirenol is capable of inhibiting the differentiation and lipogenesis of 3T3-L1 adipocytes through the activation of the Wnt/β-catenin signaling pathway, suggesting its potential as natural anti-obesity agent.

A new carbamate with cytotoxic activity from the aerial parts of Siegesbeckia pubecens

AIM

To study the chemical constituents of Siegesbeckia pubescens.

METHODS

The chemical constituents were isolated by extraction, crystallization and various chromatographic methods, and the chemical structures were elucidated on the basis of spectral analysis. In addition, the cytotoxic activity of compound 1 was evaluated using human lung cancer cell A 549.

RESULTS

Four compounds were obtained, and their structures were identified as (E)-3-(3-oxobut-1-enyl)phenyl dimethylcarbamate (1), ent-2-oxo-15, 16, 19-trihydroxypimar-8(14)-ene (2), 16-acetylkirenol (3), 3, 7-dimethylquercetin (4).

CONCLUSION

Compound 1 is a new carbamate, and the IC(50) in MTT method of compound 1 was 58 μg·mL(-1).

Discovery of structurally diverse and bioactive compounds from plant resources in China

This review describes the major discoveries of structurally diverse and/or biologically significant compounds from plant resources in China, mainly from the traditional Chinese medicines (TCMs) since the establishment of our research group in 1999. In the past decade, a large array of biologically significant and novel structures has been identified from plant resources (or TCM) in our laboratory. The structural modification of several biologically important compounds led to more than 400 derivatives, some of which exhibited significantly improved activities and provided opportunities to elucidate the structure-activity relationship of the related compound class. These findings are important for drug discovery and help us understand the biological basis for the traditional applications of these plants in TCM.

Characterization of terpenoids from the root of Ceriops tagal with antifouling activity

One new dimeric diterpenoid, 8(14)-enyl-pimar-2'(3')-en-4'(18')-en-15'(16')-endolabr- 16,15,2',3'-oxoan-16-one (1) and five known terpenoids: Tagalsin C (2), Tagalsin I (3), lup-20(29)-ene-3β,28-diol (4), 3-oxolup-20(29)-en-28-oic acid (5) and 28-hydroxylup- 20(29)-en-3-one (6) were isolated from the roots of the mangrove plant Ceriops tagal. Their structures and relative stereochemistry were elucidated by means of extensive NMR, IR and MS analysis. The antifouling activity against larval settlement of the barnacle Balanus albicostatus were evaluated using capsaicin as a positive control. All these terpenoids exhibited antifouling activity against cyprid larvae of the barnacle without significant toxicity. The structure-activity relationship results demonstrated that the order of antifouling activity was diterpenoid (Compound 2) > triterpenoid (Compounds 4, 5 and 6) > dimeric diterpenoid (Compounds 1 and 3). The functional groups on the C-28 position of lupane triterpenoid significantly affect the antifouling activity. The diterpenoid dimmer with two identical diterpenoid subunits might display more potent antifouling activity than one with two different diterpenoid subunits. The stability test showed that Compounds 2, 4, 5 and 6 remained stable over 2-month exposure under filtered seawater.

Simultaneous quantification of eight major constituents in Herba Siegesbeckiae by liquid chromatography coupled with electrospray ionization time-of-flight tandem mass spectrometry

A simple and reliable high-performance liquid chromatography coupled with electrospray ionization time-of-flight tandem mass spectrometry method was developed and validated for the determination of the major diterpenoids and flavonoids in the aerial parts of Herba Siegesbeckiae, including Kirenol, hythiemoside B, ent-16β,17,18-trihydroxy-kauran-19-oic acid, ent-17,18-dihydroxy-kauran-19-oic acid, ent-16β,17-dihydroxy-kauran-19-oic acid, 16α-hydro-ent-kauran-17,19-dioic acid, Rhamnetin, 3',4'-dimethoxy quercetin. The separation of eight compounds was performed on a Waters Symmetry Shield TM RP18 column (250mm×4.6mm i.d., 5μm) with gradient elution using a mobile phase consisting of 0.1% aqueous formic acid and acetonitrile containing 0.1% formic acid in selected ion monitoring mode. All calibration curves showed good linearity (r>0.999) within the test ranges. The precision was evaluated by intra- and inter-day tests, which revealed relative standard deviation (RSD) values less than 3.7%. The recoveries for the quantified compounds were between 97.4 and 101.2% with RSD values below 2.4%. According to the literatures, this study represents the first investigation of the simultaneous analysis of multiple components and the method can be applied to determine the amounts of the major compounds in Herba Siegesbeckiae.

ent-kaurane and ent-pimarane diterpenoids from Siegesbeckia pubescens

Phytochemical investigation of the above-ground parts of Siegesbeckia pubescens yielded 25 diterpenoids, including five new ent-pimarane diterpenoids (1-3, 11, and 12) and four new ent-kaurane diterpenoids (13-16). The structures and relative configurations of the new compounds were elucidated by comprehensive spectroscopic analysis and by comparison of their NMR data with those of related compounds. Single-crystal X-ray diffraction analysis confirmed the structures of 8, 13, and 14. Seven of these diterpenoids were evaluated for cytotoxic activity against HSC-T6, HeLa, and B16 cell lines. Compounds 11 and 14 exhibited moderate cytotoxicity.

ent-Pimarane diterpenoids from Siegesbeckia orientalis and structure revision of a related compound

Six new ent-pimarane diterpenoids, namely, ent-14beta,16-epoxy-8-pimarene-3beta,15alpha-diol (1), 7beta-hydroxydarutigenol (2), 9beta-hydroxydarutigenol (3), 16-O-acetyldarutigenol (4), 15,16-di-O-acetyldarutoside (5), and 16-O-acetyldarutoside (6), were isolated from the ethanol extract of Siegesbeckia orientalis. Their structures were elucidated on the basis of spectroscopic studies, and the absolute configuration of 1 was established by the modified Mosher's method. Furthermore, the structure of ent-12beta,16-epoxy-8-pimarene-2alpha,15beta,19-triol, recently isolated from the same plant, should be revised as ent-14beta,16-epoxy-8-pimarene-2alpha,15alpha,19-triol (10).

Antifouling metabolites from the mangrove plant Ceriops tagal

The new diterpene methoxy-ent-8(14)-pimarenely-15-one (1) and three known metabolites: ent-8(14)-pimarene-15R,16-diol (2), stigmasterol (3) and beta-sitosterol (4), were isolated from the roots of the mangrove plant Ceriops tagal. Their structures and relative stereochemistry were elucidated by means of extensive NMR, IR and MS analysis. Compounds 1, 2, 3 and 4 exhibited significant antifouling activities against cyprid larvae of the barnacle Balanus albicostatus Pilsbry, with EC(50) values of 0.32 +/- 0.01, 0.04 +/- 0.00,4.05 +/- 0.15 and 18.47 +/- 0.40 microg/cm(2), respectively, whereas their toxicities towards cyprids were very low, with LC(50 )values all above 10 microg/cm(2).

Bioactive plants from Argentina and Bolivia

Antibacterial and molluscicidal activities of methanol and chloroform extracts of 16 plant species belonging to the families Compositae and Melastomataceae were evaluated. The chloroform extract of Vernonanthura tweediana and the methanol extract of Senecio santelisis resulted to be very toxic to brine shrimp nauplii (LC(50)=1 microg/ml). Chloroform extracts of S. santelisis and Senecio leucostachys as well as the methanol extract of Wedelia subvaginata displayed molluscicidal effects on Biomphalaria peregrina showing LC(100)<100 microg/ml. Moderate antibacterial action was produced by the chloroform extracts of Flaveria bidentis, Grindelia scorzonerifolia and Vernonia incana against two strains of Staphylococcus aureus.

PTP1B inhibitory activity of kaurane diterpenes isolated from Siegesbeckia glabrescens

Protein tyrosine phosphatase 1B (PTP1B) is considered as a therapeutic target for the treatment of diabetes and obesity. In our preliminary screening study, a MeOH extract of the aerial part of Siegesbeckia glabrescens was found to inhibit PTP1B activity at 30 microg/mL. Bioassay-guided fractionation led to the isolation of two active diterpenes, ent-16betaH, 17-isobutyryloxy-kauran-19-oic acid (1) and ent-16betaH, 17-acetoxy-18-isobutyryloxy-kauran-19-oic acid (2), along with ent- 16betaH, 17-hydroxykauran-19-oic acid (3). Compounds 1 and 2 inhibited the PTP1B activity with IC50 values of 8.7 +/- 0.9 and 30.6 +/- 2.1 microM, respectively. Kinetic studies suggest that both 1 and 2 are non-competitive inhibitors of PTP1B. However, compound 3 substituted with a hydroxyl group at C-17 in kaurane-type showed no inhibitory effects towards PTP1B.

Immunosuppressive Activity of the Ethanol Extract ofSiegesbeckia orientalis on the Immune Responses to Ovalbumin in Mice

The in vitro and in vivo immunosuppressive activity of the ethanol extract of Siegesbeckia orientalis (EESO) was studied on the immune responses in mice. EESO significantly suppressed concanavalin A (Con A)- and lipopolysaccharide (LPS)-stimulated splenocyte proliferation in vitro in a concentration-dependent manner. ICR Mice were immunized subcutaneously with ovalbumin (OVA) on days 0 and 14. Beginning on the day of immunization, the mice were administered intraperitoneally with EESO at a single dose of 0.25, 0.5, and 1.0 mg at intervals of 7 days. On day 28, OVA-specific antibodies in serum, and mitogen- and OVA-induced splenocyte proliferation were measured. EESO significantly suppressed Con A-, LPS- and OVA-induced splenocyte proliferation in the OVA-immunized mice in a dose-dependent manner. The OVA-specific serum IgG, IgG1, and IgG2b levels in the OVA-immunized mice were also significantly reduced by EESO. Moreover, reducing effect on the IgG1 antibody of EESO at the dose of 1.0 mg was more significant than that of cyclosporin A (CsA; positive drug). The results suggest that EESO could suppress the cellular and humoral response to ovalbumin in mice, and deserve further investigations to be developed as immunosuppressant.