Cytotoxicity of extractives from Taiwania cryptomerioides heartwood

Antiproliferative Activity and Molecular Docking Analyses of Sesquiterpene Lactones Obtained from Activity-Directed Isolation of Centaurea saligna (K.Koch) Wagenitz in Neoplastic Cells

Secondary metabolites obtained from plants are among the most commonly encountered chemotherapeutics used in cancer treatment. Plants contain thousands of metabolites; therefore, it is important to reach the compound primarily responsible for activity by fractionating plant extracts through activity-guided isolation. The cytotoxic activities of C. saligna fractions, sub-fractions, and all pure compounds obtained from the plant were investigated in vitro using MCF-7 (human breast cancer), HeLa (human cervical cancer), and PC-3 (prostate cancer) cell lines. Eighteen compounds were isolated from C. saligna, comprising eight sesquiterpene lactones, three flavonoids, five lignans, and two phenolic compounds, with their structures elucidated through 1H-NMR, 13C-NMR, and HMBC spectroscopic techniques. The molecular docking scores of the pure compounds obtained from these sub-fractions were determined using both AutoDock and AutoDock Vina programs. It has been proven that the affinities of linichlorin B and aguerin B for Bcl-2 are higher than those of other compounds, considering the calculated Ki values and placement scores. Notable activities of linichlorin B, cynaropicrin, and aguerin B (with IC50 values of 13.67 μg/ml, 6.79 μg/ml, and 3.46 μg/ml, respectively) were detected in the PC-3 cell line; aguerin B demonstrated activity most comparable to the standard anticancer agent doxorubicin. Likewise, linichlorin B, aguerin B, and cynaropicrin demonstrated notable efficacy in the HeLa and MCF-7 cell lines, as reported by the American National Cancer Institute. Aguerin B, linichlorin B, and cynaropicrin are projected to serve as promising novel chemotherapeutic agents for cancer therapy.

Potential of 6'‑hydroxy justicidin B from Justicia procumbens as a therapeutic agent against coronavirus disease 2019

BACKGROUND

Since the onset of the coronavirus disease 2019 (COVID-19) pandemic, remarkable advances have been made in vaccine development to reduce mortality. However, therapeutic interventions for COVID-19 are comparatively limited despite these intensive efforts. Furthermore, the rapid mutation capability of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a characteristic of its RNA structure, has led to the emergence of multiple variants, necessitating a shift from a predominantly vaccine-centric approach to one that encompasses therapeutic strategies. 6'-Hydroxy justicidin B (6'-HJB), an arylnaphthalene lignan isolated from Justicia procumbens, a traditional Chinese medicine, is known for its antiviral properties.

HYPOTHESIS/PURPOSE

The aim of the present study was to assess the effectiveness and safety of 6'-HJB against SARS-CoV-2 in order to determine its potential as a therapeutic agent against COVID-19.

METHODS

The efficacy of 6'-HJB was evaluated both in vitro using Vero and Calu-3 cell lines and in vivo using ferrets. The safety assessment included toxicokinetics, safety pharmacology, and Good Laboratory Practice (GLP)-compliant toxicity evaluations following single- and repeated-dose toxicity studies in dogs.

RESULTS

The anti-SARS-CoV-2 efficacy of 6'-HJB was evaluated through dose-response curve (DRC) analysis using immunofluorescence; 6'-HJB demonstrated superior inhibition of SARS-CoV-2 growth and lower cytotoxicity than remdesivir. In SARS-CoV-2-infected ferret, 6'-HJB showed efficacy comparable to that of the positive control, Truvada. Further GLP toxicity studies corroborated the safety profile of 6'-HJB. Single-dose and 4-week repeated oral toxicity studies in Beagle dogs demonstrated minimal harmful effects at the highest dosages. The lethal dose of 6'-HJB exceeded 2,000 mg kg-1 in Beagle dogs. Toxicokinetic and GLP safety pharmacology studies demonstrated no adverse effects of 6'-HJB on metabolic processes, respiratory or central nervous systems, or cardiac functions.

CONCLUSION

This research highlights both the antiviral efficacy and safety profile of 6'-HJB, underscoring its potential as a novel COVID-19 treatment option. The potential of 6'-HJB was demonstrated using modern scientific methodologies and standards.

Insecticidal Activity and Molecular Target by Morphological Analysis, RNAseq, and Molecular Docking of the Aryltetralin Lignan Lactone Helioxanthin, Isolated from Taiwania flousiana Gaussen

Botanical insecticides are considered an environmentally friendly approach to insect control because they are easily biodegraded and cause less environmental pollution compared to traditional chemical pesticides. In this study, we reported the insecticidal activities of the ingredients from Taiwania flousiana Gaussen (T. flousiana). Five compounds, namely helioxanthin (C1), taiwanin E (C2), taiwanin H (C3), 7,4'-dimethylamentoflavone (C4), and 7,7″-di-O-methylamentoflavone (C5), were isolated and tested against the second, third, and fourth instar larvae of Aedes aegypti. Our results indicated that all five compounds showed insecticidal activities, and helioxanthin, which is an aryltetralin lignan lactone, was the most effective with LC50 values of 0.60, 2.82, and 3.12 mg/L, respectively, 48 h after application, with its activity against the second instar larvae similar to that of pyrethrin and better than that of rotenone. Further studies found that helioxanthin accumulated in the gastric cecum and the midgut and caused swelling of mitochondria with shallow matrices and fewer or disappeared crista. Additionally, our molecular mechanisms studies indicated that the significantly differentially expressed genes (DEGs) were mainly associated with mitochondria and the cuticle, among which the voltage-dependent anion-selective channel (VDAC) gene was the most down-regulated by helioxanthin, and VDAC is the potential target of helioxanthin by binding to specific amino acid residues (His 122 and Glu 147) via hydrogen bonds. We conclude that aryltetralin lignan lactone is a potential class of novel insecticides by targeting VDAC.

Antifungal Activity of Cedrol from Cunninghamia lanceolate var. konishii against Phellinus noxius and Its Mechanism

Phellinus noxius is a highly destructive fungus that causes brown root disease in trees, leading to decay and death. In Taiwan, five prized woods-Taiwania cryptomerioides, Calocedrus macrolepis var. formosana, Cunninghamia lanceolata var. konishii, Chamaecyparis formosensis, and Chamaecyparis obtusa var. formosana-are known for their fragrance and durability. This study aims to explore the anti-brown-root-rot-fungus activity of Cunninghamia lanceolata var. konishii (CL) essential oil (CLOL) and its primary components, while also delving into their mechanisms of action and inhibition pathways. The essential oil (CLOL) from CL wood demonstrated significant efficacy against P. noxius, with an inhibitory concentration (IC50) of 37.5 µg/mL. Cedrol, the major component (78.48%) in CLOL, emerged as a potent antifungal agent, surpassing the reference drug triflumizole. Further assays with cedrol revealed a stronger anti-brown-root-disease activity (IC50 = 15.7 µg/mL) than triflumizole (IC50 = 32.1 µg/mL). Scanning electron microscopy showed deformation and rupture of fungal hyphae treated with CLOL and cedrol, indicating damage to the fungal cell membrane. Cedrol-induced oxidative stress in P. noxius was evidenced by increased reactive oxygen species (ROS) levels, leading to DNA fragmentation, mitochondrial membrane potential reduction, and fungal apoptosis through the mitochondrial pathway. Gel electrophoresis confirmed cedrol-induced DNA fragmentation, whereas TUNEL staining demonstrated increased apoptosis with rising cedrol concentrations. Moreover, protein expression analysis revealed cedrol-triggered release of cytochrome c, activation of caspase-9, and subsequent caspase-3 activation, initiating a caspase cascade reaction. This groundbreaking study establishes cedrol as the first compound to induce apoptosis in P. noxius while inhibiting its growth through oxidative stress, an increase in mitochondrial membrane permeability, and activation of the mitochondrial pathway. The findings offer compelling evidence for cedrol's potential as an effective antifungal agent against the destructive brown root disease caused by P. noxius.

Savinin Triggers Programmed Cell Death of Ray Parenchyma Cells in Heartwood Formation of Taiwania cryptomerioides Hayata

The purpose of this study was to investigate the relationship between lignan biosynthesis and programmed cell death (PCD) of ray parenchyma cells during the heartwood formation of Taiwania (Taiwania cryptomerioides Hayata). Since the PCD of ray parenchyma cells and the synthesis of lignans are the two main processes involved in the formation of heartwood, both of which need to be completed through gene regulation. Based on the results of genomics and bioinformatics analysis, that the PCD of tracheids are induced by genotoxic, and the PCD of ray parenchyma cells is induced by biological factors, such as fungi, bacteria, and viruses, which could induce oxidative stress. According to the results of time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis, lignans are produced in ray parenchyma cells, and the accumulation of savinin and its downstream lignans might be the cause of PCD in ray parenchyma cells. An in vitro experiment further confirmed that the accumulation of savinin could cause protoplasts of Taiwania's xylem to produce taiwanin A, which is the marker of heartwood formation in Taiwania. Resulting in an increase in reactive oxygen species (ROS) content, which could induce oxidative stress in ray parenchyma cells and potentially lead to PCD. Based on these findings, we conclude that accumulation of savinin could be induced PCD of ray parenchyma cells in heartwood formation in Taiwania.

Bioactive Arylnaphthalide Lignans from Justicia depauperata

Eleven previously undescribed arylnaphthalide lignans (1-11) together with seven known compounds were isolated from the whole plant of Justicia depauperata. The structures of 1-11 were elucidated by spectroscopic analysis and mass spectrometry. Compounds 6 (IC₅₀ = 4.1 μM) and 9 (IC₅₀ = 9.5 μM) displayed cytotoxic activity against the KB-3-1 cervical carcinoma cell line. This report provides an insight into the conformational equilibria occurring in the arylnaphthalide lignan constituents of this plant.

Cytotoxicity and Apoptosis Induction of 6,7-Dehydroroyleanone from Taiwania cryptomerioides Bark Essential Oil in Hepatocellular Carcinoma Cells

The objective of the present study is to evaluate the cytotoxicity of Taiwania cryptomerioides essential oil and its phytochemical on the Hep G2 cell line (human hepatocellular carcinoma). Bark essential oil has significant cytotoxicity to Hep G2 cells, and S3 fraction is the most active fraction in cytotoxicity to Hep G2 cells among the six fractions. The diterpenoid quinone, 6,7-dehydroroyleanone, was isolated from the active S3 fraction by bioassay-guided isolation. 6,7-Dehydroroyleanone exhibited significant cytotoxicity in Hep G2 cells, and the efficacy of 6,7-dehydroroyleanone was better than the positive control, etoposide. Apoptosis analysis of Hep G2 cells with different treatments was characterized via flow cytometry to confirm the cell death situation. Etoposide and 6,7-dehydroroyleanone could induce the apoptosis in Hep G2 cells using flow cytometric assay. Results revealed 6,7-dehydroroyleanone from T. cryptomerioides bark essential oil can be a potential phytochemical to develop the anticancer chemotherapeutic agent for the treatment of the human hepatocellular carcinoma.

Asymmetric total synthesis of four bioactive lignans using donor–acceptor cyclopropanes and bioassay of (−)- and (+)-niranthin against hepatitis B and influenza viruses

The total synthesis of four lignans including (−)- and (+)-niranthin has been achieved utilizing cyclopropanes. Based on bioassays of the (+)- and (−)-niranthins using HBV and IFV, we speculated the bioactive site of niranthin against HBV and IFV.

Cytotoxicity, in vivo toxicity, and chemical composition of the hexane extract of Plectranthus amboinicus (Lour.) Spreng

Cancer is a universal health issue, and many anticancer therapeutic drugs have been isolated from natural products. This study analyzed the cytotoxic and apoptotic activity of Plectranthus amboinicus leaf hexane (PALH) extract in MDA-MB-231 (median inhibitory concentration [IC₅₀] = 39.26 μg/mL) and MCF7 (IC₅₀ = 89.05 μg/mL) breast cancer cell lines. Cells appeared rounded and shrunken, indicating morphological changes due to apoptosis induction. The primary constituent of PALH was phenol, 5-methyl-2-(1-methylethyl) (44%). PALH extract treatment increased the percentage of late apoptotic cells in the MDA-MB231 cell line (58% ± 1.5% at 200 μg/mL) compared to the control group, as evidenced by the activated caspase-3 and caspase-7 identified and captured by fluorescence microscopy. The relative migration rate in MDA-MB-231 cells treated with 10 μg/mL of PALH extract for 48 h was significantly lower compared to the control group. Analysis of acute (2000 mg/kg/BW) and subacute (250 and 500 mg/kg/BW) toxicity of PALH extract in mice showed no mortality or adverse effects in the kidney and liver histology compared to the control group. PALH extract can be considered nontoxic as it does not cause any adverse changes and so can be proposed as a potential breast anticancer agent.

Differential Gene Profiling of the Heartwood Formation Process in Taiwania cryptomerioides Hayata Xylem Tissues

Taiwania (Taiwania cryptomerioides) is an important tree species in Taiwan because of the excellent properties of its wood and fascinating color qualities of its heartwood (HW), as well as the bioactive compounds therein. However, limited information is available as to the HW formation of this species. The objective of this research is to analyze the differentially expressed genes (DEGs) during the HW formation process from specific Taiwania xylem tissues, and to obtain genes that might be closely associated with this process. The results indicated that our analyses have captured DEGs representative to the HW formation process of Taiwania. DEGs related to the terpenoid biosynthesis pathway were all up-regulated in the transition zone (TZ) to support the biosynthesis and accumulation of terpenoids. Many DEGs related to lignin biosynthesis, and two DEGs related to pinoresinol reductase (PrR)/pinoresinol lariciresinol reductase (PLR), were up-regulated in TZ. These DEGs together are likely involved in providing the precursors for the subsequent lignan biosynthesis. Several transcription factor-, nuclease-, and protease-encoding DEGs were also highly expressed in TZ, and these DEGs might be involved in the regulation of secondary metabolite biosynthesis and the autolysis of the cellular components of ray parenchyma cells in TZ. These results provide further insights into the process of HW formation in Taiwania.

Taiwanin E Induces Cell Cycle Arrest and Apoptosis in Arecoline/4-NQO-Induced Oral Cancer Cells Through Modulation of the ERK Signaling Pathway

Taiwanin E is a bioactive compound extracted from Taiwania cryptomerioides Hayata. In this research endeavor, we studied the anti-cancer effect of Taiwanin E against arecoline and 4-nitroquinoline-1-oxide-induced oral squamous cancer cells (OSCC), and elucidated the underlying intricacies. OSCC were treated with Taiwanin E and analyzed through MTT assay, Flow cytometry, TUNEL assay, and Western blotting for their efficacy against OSCC. Interestingly, it was found that Taiwanin E significantly attenuated the cell viability of oral cancer cells (T28); however, no significant cytotoxic effects were found for normal oral cells (N28). Further, Flow cytometry analysis showed that Taiwanin E induced G1cell cycle arrest in T28 oral cancer cells and Western blot analysis suggested that Taiwanin E considerably downregulated cell cycle regulatory proteins and activated p53, p21, and p27 proteins. Further, TUNEL and Western blot studies instigated that it induced cellular apoptosis and attenuated the p-PI3K/p-Akt survival mechanism in T28 oral cancer cells seemingly through modulation of the ERK signaling cascade. Collectively, the present study highlights the prospective therapeutic efficacy of Taiwanin E against arecoline and 4-nitroquinoline-1-oxide-induced oral cancer.

Phylogenetically distant group of terpene synthases participates in cadinene and cedrane-type sesquiterpenes accumulation in Taiwania cryptomerioides

Along with the species evolution, plants have evolved ways to produce a different collection of terpenoids to accommodate its biotic and abiotic environment, and terpene synthase (TPS) is one of the major contributors to various terpene compounds. The timber of a monotypic and relictual conifer species of Cupressace, Taiwania cryptomerioides, has excellent durability, and one of the essential factors for Taiwania to resist decay and insect pests is sesquiterpene. Compared to other conifers, Taiwania has much higher abundance of cadinene-type sesquiterpenes, and the presence of cedrene-type sesquiterpenes. To understand sesquiterpene biosynthesis in Taiwania, we functionally characterized 10 T. cryptomerioides TPSs (TcTPSs) in vivo or in planta, which could catalyze sesquiterpene formation and potentially are involved in biosynthesis of diverse sesquiterpenoids in Taiwania. The distant phylogenetic relationship and the intron loss event of TcTPSs correlate to the differentiation of chemical profile Taiwania compared to other conifers. Furthermore, we identified TcTPS3 and TcTPS12 as δ-cadinene synthase, and TcTPS6 as cedrol synthase, which demonstrates the important contributions of dynamic evolution in TPSs to the chemical diversity in plants. Combining with functional characterization and comparison of catalytic residues, we conclude at least three catalytic routes for sesquiterpene biosynthesis in this species, and the skeleton diversity has been expended in T. cryptomeriodes.

Taiwanin C elicits apoptosis in arecoline and 4-nitroquinoline-1-oxide-induced oral squamous cell carcinoma cells and hinders proliferation via epidermal growth factor receptor/PI3K suppression

Oral Squamous Cell Carcinoma (OSSC) is a major life-threatening disease with high incidence in the Southeast Asian countries. Chronic exposure to arecoline causes genetic changes in the epithelial cells of the oral mucosa, induces proliferation through activation of the EGF receptor and promotes downstream COX-2 expression. Taiwanin C, a podophyllotoxin derived from Taiwania cryptomerioides Hayata is known to inhibit COX activity and to hinder PGE2 production in macrophages. In this study a tumor cell line T28 and a non-tumor cell line N28 derived from mice OSCC models were used to study the effect of Taiwanin C on PGE₂ associated COX-2 expression and cell cycle regulators. Taiwanin C activated p21 protein expression, down-regulated cell cycle regulatory proteins, elevated apoptosis and down-regulated p-PI3K/p-Akt survival mechanism in T28 oral cancer cells. Our results therefore emphasize the therapeutic potential of Taiwanin C against arecoline-induced oral cancer.

An Ethnopharmacological, Phytochemical and Pharmacological Review on Lignans from Mexican Bursera spp

The genus Bursera belongs to the family Burseraceae and has been used in traditional Mexican medicine for treating various pathophysiological disorders. The most representative phytochemicals isolated from this genus are terpenoids and lignans. Lignans are phenolic metabolites known for their antioxidant, apoptotic, anti-cancer, anti-inflammatory, anti-bacterial, anti-viral, anti-fungal, and anti-protozoal properties. Though the genus includes more than 100 species, we have attempted to summarize the biological activities of the 34 lignans isolated from selected Mexican Bursera plants.

Ethnobotany, phytochemistry and pharmacology of Arctotis arctotoides (L.f.) O. Hoffm.: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Arctotis arctotoides (Asteraceae) is part of the genus Arctotis. Arctotis is an African genus of approximately 70 species that occur widely in the African continent with diverse medicinal values. This plant is used for the treatment of indigestion and catarrh of the stomach, epilepsy, topical wounds and skin disorders among the ethnic groups in South Africa and reported to have a wide spectrum of pharmacological properties.

AIM OF THE REVIEW

The aim of the present review is to appraise the botany, traditional uses, phytochemistry, pharmacological potential, analytical methods and safety issues of A. arctotoides. Additionally, this review will help to fill the existing gaps in knowledge and highlight further research prospects in the field of phytochemistry and pharmacology.

MATERIALS AND METHODS

Information on A. arctotoides was collected from various resources, including books on African medicinal herbs and Zulu medicinal plants, theses, reports and the internet databases such as SciFinder, Google Scholar, Pubmed, Scopus, Web of Science, and Mendeley by using a combination of various meaningful keywords. This review surveys the available literature of the species from 1962 to April 2017.

RESULTS

In vitro and in vivo studies of the medicinal properties of A. arctotoides were reviewed. The main isolated and identified compounds were reported as sesquiterpenes, farnesol derivatives, germacranolide, guaianolides and some steroids, of which, nine were reported as antimicrobial. Monoterpenoids and sesquiterpenoids were the predominant essential oil compound classes of the leaves, flowers, stems and roots. The present review revealed potential pharmacological properties such as anti-oxidant, antibacterial, antifungal and anticancer activities of plant extracts as well as isolated compounds. Moreover, the review reports the safety profile (toxicity) of the crude extracts that had been screened on brine shrimps, rats and human cell lines.

CONCLUSIONS

The present review has focused on the phytochemistry, botany, ethnopharmacology, biological activities and toxicological information of A. arctotoides. On the basis of reported data, A. arctotoides has emerged as a good source of natural medicine for the treatment of microbial infections, skin diseases, anti-inflammatory and anticancer agents and also provides new insights for further isolation of new bioactive compounds, especially the discovery of antimicrobial, anti-inflammatory and anticancer novel therapeutic lead drug molecules. Additionally, intensive investigations regarding pharmacological properties, safety assessment and efficacy with their mechanism of action could be future research interests before starting clinical trials for medicinal practices.

Justicia procumbens Extract (DW2008) Selectively Suppresses Th2 Cytokines in Splenocytes and Ameliorates Ovalbumin-Induced Airway Inflammation in a Mouse Model of Asthma

DW2008 is an anhydrous ethanol extract of Justicia procumbens produced by Dong-Wha Pharmaceutical, Inc., Co. as a candidate anti-asthmatic drug. In this study, DW2008 selectively reduced T helper 2 (Th2) cytokines in mouse splenocytes and ameliorated ovalbumin-induced airway inflammation by downregulating pulmonary infiltration of differential inflammatory cells and Th2 cytokines more than a decoction or ethanol extract of J. procumbens did in a mouse asthma model. DW2008 also significantly inhibited airway hyperresponsiveness and reduced the thickness of the airway epithelium. HPLC analysis showed that the major peaks (justicidin A and B) of DW2008 were higher than those of the other extracts. Justicidin A and B significantly suppressed Th2 cytokine levels in mouse spleen cells and exhibited a protective effect in ovalbumin-induced airway inflammation. Our findings indicate that DW2008 effectively inhibits allergic airway inflammatory reactions and airway hyperresponsiveness in a mouse model of asthma, suggesting its potential as an anti-asthmatic agent.

Enantiomeric trans β-aryl-δ-iodo-γ-lactones derived from 2,5-dimethylbenzaldehyde induce apoptosis in canine lymphoma cell lines by downregulation of anti-apoptotic Bcl-2 family members Bcl-xL and Bcl-2

For many years, studies focused on developing new natural or synthetic compounds with antineoplastic activity have attracted the attention of researchers. An interesting group of such compounds seem to be those with both lactone moiety and an aromatic ring which, in addition to antimicrobial or antiviral activity, also exhibit antitumor properties. The study shows antitumor activity of two enantiomeric trans isomers of 5-(1-iodoethyl)-4-(2',5'-dimethylphenyl)dihydrofuran-2-one. Our aim was to determine their antitumor activity manifested as an ability to induce apoptosis in selected canine cancer cell lines as well as to evaluate differences in their strength depending on the configuration of their stereogenic centers. The enantiomers (+)-(4R,5S,6R)-1 and (-)-(4S,5R,6S)-2 were found to induce classical caspase-dependent apoptosis through downregulation of the expression of anti-apoptotic proteins Bcl-xL and Bcl-2. Although the mechanism of apoptosis induction was the same for both enantiomers, they differed in their strength, as stronger antineoplastic activity in vitro was exhibited by isomer (+)-(4R,5S,6R)-1.

Chemical Composition of the Essential Oil of Phyllanthus acidus

The essential oil from the leaves of Phyllanthus acidus (Phyllanthaceae) was obtained by hydrodistillation and its composition determined by GC and GC/MS. Twenty-one compounds were identified, representing 92.8 % of the oil. The most abundant components were t -muurolol (20.4 %), α-cadinol (14.6 %), β-cadinene (8.9 %) and α-muurolene (7.5 %).

Taiwanin E inhibits cell migration in human LoVo colon cancer cells by suppressing MMP-2/9 expression via p38 MAPK pathway

Taiwanin E is a natural compound which is structurally analogous to estrogen II and is abundantly found in Taiwania cryptomerioides. It has been previously reported for its anticancer effects; however, the pharmaceutical effect of Taiwanin E on Human LoVo colon cancer cells is not clear. In this study, we investigated the effects of Taiwanin E on metastasis and the associated mechanism of action on Human LoVo colon cancer cells with respect to the modulations in their cell migration and signaling pathways associated with migration. The results showed that Taiwanin E inhibited cell migration ability correlated with reduced expression and activity of MMP-2 and MMP-9. In addition, Taiwanin E induced activation of p38 through phosphorylation. Inhibition of p38α/β significantly abolished the effect of Taiwanin E on cell migration and MMP-2/-9 activity. Our results conclude that Taiwanin E inhibited cell migration chiefly via p38α MAPK pathway and in a lesser extend via p38β MAPK. The results elucidate the potential of the phytoestrogen natural compound Taiwanin E as a cancer therapeutic agent in inhibiting the cell migration. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 2021-2031, 2017.

Composition, in vitro Cytotoxicity, Anti-mildew and Anti-wood-decay Fungal Activities of the Fruit Essential Oil of Liquidambar formosana from Taiwan

This study investigated the chemical composition, in vitro cytotoxicity, anti-mildew, and anti-wood-decay fungal activities of the essential oil isolated from the fruit of Liquidambar formosana from Taiwan. The essential oil from the fresh fruit was isolated using hydrodistillation in a Clevenger-type apparatus, and characterized by GC-FID and GC-MS. A total of 45 compounds were identified, representing 98.5% of the essential oil. The main components identified were α-pinene (16.8%), β-caryophyllene (10.1%), τ-muurolol (8.3%), τ-cadinol (7.6%), β-pinene (6.7%), and sabinene (5.7%). The essential oil exhibited cytotoxic activity against human oral, liver, and lung cancer cells. The active source compounds were β-caryophyllene, τ-cadinol, and τ-muurolol. The fruit essential oil was shown to have excellent anti-mildew and anti-wood-decay fungal activities, the active compounds being evaluated as τ-cadinol and τ-muurolol.

Taiwanin C selectively inhibits arecoline and 4-NQO-induced oral cancer cell proliferation via ERK1/2 inactivation

Arecoline, the most abundant alkaloid in betel nut is known to promote abnormal proliferation of epithelial cells by enhancing epidermal growth factor receptor (EGFR) activation and cyclooxygenase-2 (COX2) expression. Taiwanin C, a naturally occurring lignan extracted from Taiwania cryptomerioides, has been found to be a potential inhibitor of COX2 expression. Based on the MTT assay results, taiwanin C was found to be effective in inhibiting the tumorous T28 cell than the non-tumorous N28 cells. The modulations in the expression of relevant proteins were determined to understand the mechanism induced by taiwanin C to inhibit T28 cell proliferation. The levels of activated EGFR and COX2 were found to be abnormally high in the T28 oral cancer cells. However, taiwanin C was found to inhibit the activation of EGFR and regulated other related downstream proteins and thereby inhibited the T28 cell proliferation. In conclusion the results indicate that taiwanin C suppresses COX2-EGFR and enhances P27 pathways to suppress arecoline induced oral cancer cell proliferation via ERK1/2 inactivation. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 62-69, 2017.

Helioxanthin suppresses the cross talk of COX-2/PGE2 and EGFR/ERK pathway to inhibit Arecoline-induced Oral Cancer Cell (T28) proliferation and blocks tumor growth in xenografted nude mice

Helioxanthin, an active compound from Taiwania cryptomerioides Hayata, has been shown to have various biological activities. However, their anticancer effect in oral squamous cell carcinoma has not been well established yet. Helioxanthin inhibited the proliferation of oral squamous cell carcinoma cells in a dose-dependent manner by inducing G2/M phase arrest. Similarly, helioxanthin inhibited cyclooxygenase-2, (COX-2), phosphorylated EGFR, and extracellular-signal-regulated kinases (ERK) protein level and further reduced the nuclear accumulation of phosphorylated epidermal growth factor receptor (pEGFR) and activator protein-1(AP-1) family protein, c-fos. Moreover, helioxanthin at the dose of 20 and 30 mg kg^-1 for 15 days reduced the tumor growth in animal model. This study demonstrated that Helioxanthin exerts its anticancer activity against oral cancer cells by downregulating EGFR/ERK/c-fos signaling pathway to inhibit COX-2 level and by activating cyclin-dependent kinase inhibitor (p27) to further induce G2/M cell cycle arrest. This helioxanthin may serve as a novel candidate for oral cancer prevention. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 2045-2056, 2016.

Optically active stereoisomers of 5-(1-iodoethyl)-4-(4'-isopropylphenyl)dihydrofuran-2-one: The effect of the configuration of stereocenters on apoptosis induction in canine cancer cell lines

Four stereoisomers of δ-iodo-γ-lactones with p-isopropylphenyl substituent at β-position: cis-(4R,5R,6S)-1, cis-(4S,5S,6R)-2, trans-(4R,5S,6R)-3, trans-(4S,5R,6S)-4 with proved antiproliferative activity were subjected to in vitro tests for a better understanding of their anticancer activity. The subject of our interest was a possible relationship between a configuration of chiral centers of the studied lactones and their anticancer potency against a panel of canine cell lines representing hematopoietic (CLBL-1, GL-1, CL-1, CLB70) and mammary gland cancers (P114, CMT-U27, CMT-U309). To determine the anticancer activity of the tested compounds, cell viability and cell metabolic activity were checked using propidium iodide staining and the MTT test. To determine whether the studied compounds cause necrotic or apoptotic cell death, two assays for apoptosis evaluation were performed, annexin V staining and detection of caspase 3/7 activation. Simultaneously, the effects of the compounds on the cell cycle were also examined. The conducted research confirmed the anticancer potential of the tested lactones against canine cancers. The investigated isomers exerted higher activity against canine lymphoma/leukemia cell lines than against mammary tumors, whereas the configuration of stereogenic centers of the examined compounds affected their activity. It has been shown that stereoisomers with 4S configuration (2,4) were more active, and the most potent one was the cis-(4S,5S,6R)-2 isomer. The investigated lactones seemed to initiate the process of apoptosis rather than acting as typical cytostatic agents, as cell death via apoptosis, and no increase in G2-M population in the cell cycle analysis were observed. The presented study demonstrated that all four stereoisomers of δ-iodo-γ-lactones with p-isopropylphenyl substituent at β-position induced apoptosis via a mitochondrial-mediated, caspase-dependent pathway.

Down-regulation of β-catenin and the associated migration ability by Taiwanin C in arecoline and 4-NQO-induced oral cancer cells via GSK-3β activation

Cancer is one of the leading causes of death worldwide, and oral squamous cell carcinoma (OSCC) accounts for almost a sixth of all reported cancers. Arecoline, from areca nut is known to enhance carcinogenesis in oral squamous cells. The objective of this study is to determine the effect of Taiwanin C, from Taiwania cryptomerioides Hayata against Arecoline-associated carcinogenesis. An OSCC model was created in C57BL/6J Narl mice by administrating 0.5 mg mL^-1 arecoline with 0.2 mg mL^-1 4-NQO carcinogen for 8 and 28 wk to mimic the etiology of oral cancer patients in Asia. Mice were sacrificed and two cell lines, T28 from the tumor and N28 cancerous cell line from the surrounding non tumor area, were established. Taiwanin C showed effective anti-tumor activity in nude mice models. Taiwanin C significantly inhibited the cell viability of T28 cells in a dose dependent manner, but did not inflict any effect on N28 normal cells. Taiwanin C treatment inhibited the migration ability of T28 cells in a dose dependent manner as determined by wound healing and migration assays. Taiwanin C also reduced the levels of β-catenin and its downstream metastatic proteins, Tbx3 and c-Myc. Besides, Taiwanin C inhibited the nuclear accumulation of β-catenin and induced β-catenin degradation via proteasome-mediated pathway. Moreover, Taiwanin C enhanced GSK-3β and reduced the p-ser⁹ GSK-3β protein level to inactivate Wnt signaling. Taken together, Taiwanin C blocked the cell migration effects of T28 cells mediated through the activation of GSK-3β to enhance protein degradation and reduce nuclear accumulation of β-catenin. © 2016 Wiley Periodicals, Inc.

Composition of the Leaf Essential Oil of Phoebe formosana from Taiwan and its in vitro Cytotoxic, Antibacterial, and Antifungal Activities

The essential oil from the leaves of Phoebe formosana from Taiwan was isolated using hydrodistillation in a Clevenger-type apparatus, and characterized by GC-FID and GC-MS. Seventy-one compounds were identified, representing 100% of the oil. The main components identified were α-humulene (16.8%), τ-cadinol (8.9%), α-pinene (8.4%), α-cadinol (8.1%), β-caryophyllene (8.0%), β-phellandrene (6.0%), and β-eudesmol (5.8%). The oil exhibited cytotoxic activity against human lung, liver and oral cancer cells. The active compounds were β-caryophyllene, α-humulene, τ-cadinol, β-eudesmol, and α-cadinol. The antibacterial activity of the oil was tested by the disc diffusion and micro-broth dilution methods against eight bacterial species. The oil exhibited moderate growth suppression against Gram-positive bacteria with inhibition zones of 28 to 36 mm, and MIC values of 250 to 375 μg/mL. The active antibacterial compounds were determined to be τ-cadinol, β-eudesmol, and α-cadinol. The leaf oil displayed excellent antifungal activity with the active compounds determined as α-cadinol, β-eudesmol, τ-cadinol, α-humulene, and β-caryophyllene.

Composition, in vitro Cytotoxic, and Antimicrobial Activities of the Flower Essential Oil of Diospyros discolor from Taiwan

This study investigated the chemical composition, in vitro cytotoxic, and antimicrobial activities of the essential oil isolated from the flower of Diospyros discolor from Taiwan. The essential oil was isolated using hydrodistillation in a Clevenger-type apparatus, and characterized by GC-FID and GC-MS. Twenty-eight compounds were identified, representing 100% of the oil. The main components identified were (2 Z,6 E)-farnesol (35.0%), α-cadinol (10.9%), ( E)-nerolidol (6.9%), α-humulene (6.0%), τ-cadinol (5.6%), β-caryophyllene (5.3%), and τ-muurolol (5.3%). The oil exhibited cytotoxic activity against human colon, liver, and lung cancer cells. The active compounds were β-caryophyllene, α-humulene, τ-cadinol, τ-muurolol, α-cadinol, and (2 Z,6 E)-farnesol. The antimicrobial activity of the oil was tested by the disc diffusion and micro-broth dilution methods against ten microbial species. The oil exhibited moderate to strong growth suppression against Bacillus cereus, Staphylococcus aureus, S. epidermidis, Escherichia coli, Enterobacter aerogenes, and Candida albicans, with inhibition zones of 40 to 52 mm and MIC values of 31.25–62.5 μg/mL, respectively. For the antimicrobial activities of the oil, the active compounds were determined to be α-cadinol, τ-cadinol, τ-muurolol and (2 Z,6 E)-farnesol.

Activation and Inhibition of ATM by Phytochemicals: Awakening and Sleeping the Guardian Angel Naturally

Double-stranded breaks (DSBs) are cytotoxic DNA lesions caused by oxygen radicals, ionizing radiation, and radiomimetic chemicals. Increasing understanding of DNA damage signaling has provided an ever-expanding list of modulators reported to orchestrate DNA damage repair and ataxia telangiectasia mutated (ATM) is the master regulator and main transducer of the DSB response. Increasingly, it is being realized that DNA damage response is a synchronized and branched network that functionalizes different molecular cascades to activate special checkpoints, thus temporarily arresting progression of the cell cycle while damage is being assessed and processed. It is noteworthy that both nutrigenetics and nutrigenomics have revolutionized the field of molecular biology and rapidly accumulating experimental evidence has started to shed light on biological activities of a wide range of phytochemicals reported to modulate cell cycle, DNA repair, cell growth, differentiation and apoptosis as evidenced by cell-based studies. In this review, we have attempted to provide an overview of DNA damage signaling, how ATM signaling regulates tumor necrosis factors-related apoptosis inducing ligand (TRAIL)-induced intracellular network. We also illuminate on how resveratrol, epigallocatechin gallate, curcumin, jaceosidin, cucurbitacin, apigenin, genistein, and others trigger activation of ATM in different cancer cells as well as agents for ATM inactivation. Understanding the interplay of TRAIL-induced intracellular signaling and ATM modulation of downstream effectors is very important. This holds particularly for a reconceptualization of the apparently paradoxical roles and therapeutically targetable for enhancing the response to DNA damage-inducing therapy.

A Combined Transition-Metal-Catalyzed and Photopromoted Process: Synthesis of 2,3-Fused 4-Phenylnaphthalen-1-yl Carboxylates from 1,7-Diaryl-1,6-diynes

2,3-Fused 4-phenylnaphthalen-1-yl carboxylates were synthesized in a step- and atom-economical manner using a ruthenium-catalyzed hydrocarboxylative cyclization of 1,7-diaryl-1,6-diynes and subsequent oxidative photocyclization. The scope of this novel two-step process was demonstrated by the construction of diverse structures from substrates with various tethers and terminal aryl groups. Late-stage CH functionalizations of the arylnaphthalene product further enhance the synthetic potential of the developed process.

Asymmetric total syntheses of megacerotonic acid and shimobashiric acid A

The asymmetric total syntheses of the α-benzylidene-γ-butyrolactone natural products megacerotonic acid and shimobashiric acid A have been accomplished in nine and 11 steps, respectively, from simple, commercially available starting materials. The key step for each synthesis is the (arene)RuCl(monosulfonamide)-catalyzed dynamic kinetic resolution-asymmetric transfer hydrogenation (DKR-ATH) of racemic α,δ-diketo-β-aryl esters to establish the absolute stereochemistry. Intramolecular diastereoselective Dieckmann cyclization forms the lactone core, and ketone reduction/alcohol elimination installs the α-arylidene.

Essential Oil from the Heartwood of Taiwan fir Ameliorates LPS-induced Inflammatory Response by Inhibiting the Activation of Mitogen-activated Protein Kinase

The essential oil from the heartwood of Taiwan fir (EOTC) was demonstrated to exhibit anti-inflammatory activity in lipopolysaccharide (LPS)-activated mouse macrophages. EOTC reduced nitrite oxide levels and inducible nitrite oxide synthase expression in, and tumor necrosis factor-α and interleukin-6 secretion by, LPS-activated macrophages without affecting cyclooxygenase-2 expression. EOTC reduced the levels of interleukin-1β precursor induced by LPS and decreased the NLRP3 inflammasome-derived interleukin-1β secretion induced by LPS and adenosine triphosphate. In addition, the phosphorylation levels of ERK1/2, JNK1/2, and p38 in LPS-activated macrophages were reduced by EOTC. Furthermore, EOTC was composed of oxygenated sesquiterpenes (68.4%), sesquiterpene hydrocarbons (28.9%) and diterpenes (0.9%). The major compounds of the oxygenated sesquiterpenes were τ-cadinol (23.9%), α-cadinol (21.1%) and cedrol (16.9%). These findings suggest that EOTC may be a candidate for the development of anti-inflammatory agents for preventing and ameliorating inflammation-related diseases.

Hinokinin, an emerging bioactive lignan

Hinokinin is a lignan isolated from several plant species that has been recently investigated in order to establish its biological activities. So far, its cytotoxicity, its anti-inflammatory and antimicrobial activities have been studied. Particularly interesting is its notable anti-trypanosomal activity.

Persea declinata (Bl.) Kosterm Bark Crude Extract Induces Apoptosis in MCF-7 Cells via G0/G1 Cell Cycle Arrest, Bcl-2/Bax/Bcl-xl Signaling Pathways, and ROS Generation

Persea declinata (Bl.) Kosterm is a member of the Lauraceae family, widely distributed in Southeast Asia. It is from the same genus with avocado (Persea americana Mill), which is widely consumed as food and for medicinal purposes. In the present study, we examined the anticancer properties of Persea declinata (Bl.) Kosterm bark methanolic crude extract (PDM). PDM exhibited a potent antiproliferative effect in MCF-7 human breast cancer cells, with an IC₅₀ value of 16.68 µg/mL after 48 h of treatment. We observed that PDM caused cell cycle arrest and subsequent apoptosis in MCF-7 cells, as exhibited by increased population at G₀/G₁ phase, higher lactate dehydrogenase (LDH) release, and DNA fragmentation. Mechanistic studies showed that PDM caused significant elevation in ROS production, leading to perturbation of mitochondrial membrane potential, cell permeability, and activation of caspases-3/7. On the other hand, real-time PCR and Western blot analysis showed that PDM treatment increased the expression of the proapoptotic molecule, Bax, but decreased the expression of prosurvival proteins, Bcl-2 and Bcl-xL, in a dose-dependent manner. These findings imply that PDM could inhibit proliferation in MCF-7 cells via cell cycle arrest and apoptosis induction, indicating its potential as a therapeutic agent worthy of further development.

An improved bioassay facilitates the screening of repellents against cat flea, Ctenocephalides felis (Siphonaptera: Pulicidae)

BACKGROUND

Repellents are a common method for preventing flea bites, making an effective system for flea repellent screening advantageous. We describe an improved technique to facilitate repellent activity screening of numerous plant-based Ctenocephalides felis (cat flea) repellents.

RESULTS

Two long strips of filter paper were impregnated with test compounds (dissolved in ethanol) and ethanol only, respectively. After drying, the two filter papers were glued together along the long side and inserted into a glass tube containing non-fed cat fleas. The distribution of cat fleas in each half of the filter paper was recorded after 30 min to calculate repellency. Results showed that the essential oil of Cinnamomum osmophloeum (from leaf), Taiwania cryptomerioides (from heartwood) and Plectranthus amboinicus (from leaf) exhibits repellent activity against cat fleas in a dose dependent manner. Moreover, the repellent activities against cat fleas of 2% trans-cinnamaldehyde (the main constituent of Ci. osmophloeum essential oil) and 0.5% thymol (the main constituent of P. amboinicus essential oil) are 97.6% and 90.6%, and can persist for up to 4 and 8 h, respectively. These results are comparable to those of 15% DEET.

CONCLUSION

The proposed screening technique can facilitate the pre-screening of numerous flea repellents for further evaluation on animal or human subjects.

Composition and in vitro Anticancer Activities of the Leaf Essential Oil of Neolitsea variabillima from Taiwan

This study investigated the chemical composition and in vitro anticancer activities of the essential oil isolated from the leaf of Neolitsea variabillima. The essential oil was isolated using hydrodistillation in a Clevenger-type apparatus, and characterized by GC-FID and GC-MS. Sixty-seven compounds were identified, representing 100% of the oil. The main components identified were trans-β-ocimene (13.4%), α-cadinol (10.5%), terpinen-4-ol (9.3%), τ-cadinol (9.2%), β-caryophyllene (8.8%), and sabinene (6.7%). The anticancer activities of oil were evaluated. The results showed that the oil exhibited cytotoxic activity against human oral, liver, lung, colon, melanoma, and leukemic cancer cells. The presence of β-caryophyllene, τ-cadinol, and α-cadinol significantly contributed to the anticancer activities of N. variabillima leaf oil.

Highly stereoselective synthesis of (Z)- and (E)-chloro-substituted-α-methylene-γ-butyrolactone by possibly controlling cis- and trans-chloropalladation

A palladium-catalyzed selective synthesis of cis- or trans-chloro-substituted-α-methylene-γ-butyrolactones from single substrate (propiolic acid) has been realized by controlling cis- or trans-chloropalladation. This method is highly effective for building C-Cl, C-O, and C-C bonds into a one-pot procedure because of its good atom and step efficiency.

Role of JNK and p38 MAPK in Taiwanin A-induced cell death

AIM

The lignan compound Taiwanin A is cytotoxic for human cancer cells. Taiwanin A has been previously shown to damage microtubules, induce mitotic arrest and cause apoptosis in cancer cells. The goal of the current study is to identify intracellular signaling pathways that are involved in Taiwanin A-mediated apoptosis.

MAIN METHODS

We examined the activation of three mitogen-activated protein kinases (MAPKs), extracellular signal-regulated kinase (ERK), p38 and c-Jun N-terminal kinase (JNK), in HepG2 cells after Taiwanin A treatment. The role of MAPK activation in Taiwanin A-induced apoptosis was examined using Western blotting, caspase activity assays combined with specific MAPK inhibitors and shRNA treatment to knockdown JNK.

KEY FINDINGS

Taiwanin A activated all three MAPKs (ERK, p38 and JNK). Cytotoxicity was blocked by the p38 MAPK inhibitor SB203580 and the JNK inhibitor SP600125 but not by the ERK inhibitor PD98059. A combined treatment of SB203580 and SP600125 showed increased effects on the inhibition of Taiwanin A cytotoxicity, suggesting that both JNK and p38 play a role in Taiwanin A-induced apoptosis. Inhibition of p38 activity reduced Taiwanin A-induced p53 phosphorylation on Ser15. Direct interaction of Taiwanin A-activated p38 and p53 was demonstrated by immunoprecipitation. In addition, inhibition of JNK by SP600125 or silencing of the JNK scaffold protein JIP2 reduced phosphorylation of Bcl-2, which may help to promote anti-apoptotic pathways.

SIGNIFICANCE

We demonstrated for the first time that two distinct apoptotic pathways, the p38-p53 and JNK-Bcl-2 pathways, were triggered by the anti-microtubule compound Taiwanin A.

Composition, Antioxidant, Antimicrobial and Anti-wood-decay Fungal Activities of the Twig Essential Oil of Taiwania cryptomerioides from Taiwan

This study investigated the chemical composition, antioxidant, antimicrobial and anti-wood-decay fungal activities of the essential oil isolated from the twigs of Taiwania cryptomerioides from Taiwan. The essential oil was isolated using hydrodistillation in a Clevenger-type apparatus, and characterized by GC-FID and GC-MS. A total of 35 compounds were identified, representing 100% of the oil. The main components identified were α-cadinol (45.9%), ferruginol (18.9%) and β-eudesmol (10.8%). The antioxidant activity of the oil was tested by the DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging capability test. The results showed an IC50 of 90.8 ± 0.2 μg/mL. The active source compound was ferruginol. The antimicrobial activity of the oil was tested by the disc diffusion and micro-broth dilution methods against ten microbial species. The oil exhibited strong growth suppression against Gram-positive bacteria and yeast with inhibition zones of 45~52 mm and MIC values of 31.25~62.5 μg/mL, respectively. The anti-wood-decay fungal activity of the oil was also evaluated. The oil demonstrated excellent activity against four wood-decay-fungal species. For the antimicrobial and anti-wood-decay fungal activities of the oil, the active source compounds were determined to be α-cadinol, β-eudesmol and ferruginol.

Miscellaneous terpenoid constituents of Abies nephrolepis and their moderate cytotoxic activities

Three monoterpenoids and two triterpenoids were isolated from Abies nephrolepis together with 53 known terpenoids. The structures of the compounds were established by 1D and 2D NMR spectroscopy. The absolute configuration of 3-hydroxycamphane-2-carboxylic acid was established as (1S,2R,3S,4R) by Cu-Kα X-ray crystallography. All 58 isolates were tested for cytotoxic activity against four tumor cells viz. A549 (human lung adenocarcinoma), Colo205 (colon adenocarcinoma), QGY-7703 (human hepatoma) and THP-1 (human monocytic leukemia). α-Cadinol exhibited the best effects on A549, Colo205 and QGY-7703 with IC(50) values of 8.6, 8.1 and 4.6 μg/mL, respectively.

Taiwanin A inhibits MCF-7 cancer cell activity through induction of oxidative stress, upregulation of DNA damage checkpoint kinases, and activation of p53 and FasL/Fas signaling pathways

This study investigates the anti-MCF-7 breast cancer cell effects and the underlying pharmacological activity and mechanism of taiwanin A, a major lignan isolated from Taiwania cryptomerioides. Our results show that taiwanin A time-dependently induced reactive oxygen species level and DNA damage in MCF-7 cells, which were likely activated kinases ataxia telangiectasia mutated (ATM) and checkpoint kinase (Chk). Taiwanin A could also up-regulate p53, phosphorylated p53, p21(Cip1), and p27(Kip1) and down-regulate the G(2)/M checkpoint cyclin-dependent kinase1 (Cdk1)-cyclin A/B, leading to induction of G(2)/M cell-cycle arrest in MCF-7 cells. Blockade of p53 gene expression by siRNA further demonstrated that the cell-cycle arrest induced by taiwanin A was p53-dependent. The FasL/Fas-mediated apoptotic signaling cascade was involved in taiwanin A-induced apoptosis via activation of caspases-10 and -7 (but not caspase-8), and proteolytic cleavage of poly(ADP-ribose) polymerase (PARP). In contrast, mitochondria-initiated apoptotic pathway was not involved. This is the first report to delineate novel mechanism of the action of taiwanin A against MCF-7 cells, suggesting this lignan may have value for development as an anti-breast cancer agent.

Arylnaphthalene lignans from Taiwania cryptomerioides as novel blockers of voltage-gated K+ channels

Lignans are natural phytochemicals which exhibit multiple pharmacological effects such as anti-inflammation, antivirus and anti-tumor activities. Whether they have effects on neural tissues and ion channels is still unknown. The effects of several arylnaphathalene lignans purified from Taiwania cryptomerioides on voltage-gated K(+) (Kv) channels in mouse neuroblastoma N2A cells were examined. These lignans included Taiwanin E, helioxanthin (HXT) and diphyllin. All lignans showed inhibitory effects on Kv channels and HXT was the most potent compound (IC(50)=1.7 μM). The mechanism of HXT block was further investigated. Its action was found to be extracellular but not intracellular. HXT accelerated current decay, caused a left-shift in steady-state inactivation curve but had no effect on voltage-dependence of activation. HXT block was unaffected by intracellular K(+) concentrations. Further, it did not affect ATP-sensitive K(+) channels. Our data therefore suggest that HXT is a potent and specific blocker of Kv channels, possibly with an inhibitory mechanism involving acceleration of slow inactivation.