Lignans with Anti-Hepatitis B Virus Activities from Phyllanthus niruri L

Antiviral Activity of Natural Herbs and their Isolated BioactiveCompounds: A Review

Viruses are the cause of many human pathogenesis-related conditions. A serious hazard to public health has been created because of the increase in worldwide travel, fast urbanization, and infectious epidemics. At the same time, no preventative vaccines or antiviral treatments are currently available. Resources for developing new antiviral medications can be found in enhanced natural products and herbal medicines. These natural substances have aided the research on developing preventive vaccines and antiviral treatments. Based primarily on in vitro and in vivo searches, this review aims to explore the antiviral properties of plant extracts and some isolated plant natural products. Only a few antiviral medications have been given clinical approval, while numerous viruses continue to elude adequate immunization. Therefore, developing novel antiviral medicines is crucial, and natural substances make excellent sources for these new drugs. This review highlights various natural herbal drugs possessing antiviral properties.

The antiviral potential of Phyllanthus species: a systematic review

Viral infections and diseases caused by viruses are worldwide problems. According to a WHO report, three to five million people are chronically infected with hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV) each year globally. Since some viruses mutate very quickly, developing antiviral drugs can be a daunting task. Moreover, currently used synthetic drugs are toxic and associated with side effects. Therefore, there is a need to search for alternative natural remedies that have low toxicity, a new mechanism of action, and no major side effects. Phyllanthus plants have traditionally been used to treat viral hepatitis and liver damage in many tropical and subtropical countries worldwide. In this review, we discuss the therapeutic potential of Phyllanthus spp. against HBV, HCV, HIV, herpes simplex virus, and SARS-CoV-2. The inferences from in vitro and in vivo studies and clinical trials validate the use of Phyllanthus in antiviral remedies.

Phyllanthus amarus shoot cultures as a source of biologically active lignans: the influence of selected plant growth regulators

This is the first comprehensive study of the influence of plant growth regulators (PGRs) on the development of shoots and accumulation of biologically active lignans—phyllanthin and hypophyllanthin, in the shoot culture of P. amarus Schum. & Thonn. (Euphorbiaceae) obtained by direct organogenesis. The following PGRs were included in the experiments—cytokinins: kinetin (Kin), 6-benzylaminopurine (BAP), 2-isopentenyladenine (2iP), 1-phenyl-3-(1,2,3-thiadiazol-5-yl)urea, thidiazuron (TDZ) and auxin, indole-3-butyric acid (IBA) and used at various concentrations. Depending on PGRs and their concentrations, differences in the culture response and lignan accumulation were observed. The highest content of the investigated compounds was found in the shoot culture grown on Murashige and Skoog’s (MS) medium supplemented with Kin 0.25 mg/L. The sum of phyllanthin and hypophyllanthin was  ~ 10 mg/g of dry weight (DW), which was similar or even higher than that in the plant material obtained from natural conditions. The results of the research provide new data on the selection of the optimal growth medium for the production of plant material with a significant level of phyllanthin and hypophyllanthin biosynthesis. The obtained data may also be valuable in designing systems for large-scale cultivation of P. amarus shoots with high productivity of hepatoprotective lignans.

Hepatoprotective Native Plants Documented in Brazilian Traditional Medicine Literature: Current Knowledge and Prospects

The native flora of Brazil covers a large biodiversity of plants, some of which have important pharmacological properties. Ethnobotanical studies have established that the folk use of plants for hepatobiliary disorders is very common in Brazil. This review aimed to compile, describe and discuss the main native Brazilian medicinal plants used as hepatoprotective agents listed on 25 books by authors from various regions in the country. Based on the 153 species found, a comprehensive analysis of the most relevant scientific studies is presented, including Piper umbellatum, Echinodorus macrophyllus, Fevillea trilobata and Achyrocline satureioides. Some medicinal plants share both a large number of citations and scientific evidence to corroborate their hepatoprotective effects, including Solanum paniculatum, Baccharis crispa and Phyllanthus niruri, which could be of interest to develop new phytomedicines. Additionally, some active ingredients are indicated as being responsible for the liver protective effects described, particularly phenolic compounds (flavonoids, coumestans and lignans).

Plant-derived lignans as potential antiviral agents: a systematic review

Medicinal plants are one of the most important sources of antiviral agents and lead compounds. Lignans are a large class of natural compounds comprising two phenyl propane units. Many of them have demonstrated biological activities, and some of them have even been developed as therapeutic drugs. In this review, 630 lignans, including those obtained from medicinal plants and their chemical derivatives, were systematically reviewed for their antiviral activity and mechanism of action. The compounds discussed herein were published in articles between 1998 and 2020. The articles were identified using both database searches (e.g., Web of Science, Pub Med and Scifinder) using key words such as: antiviral activity, antiviral effects, lignans, HBV, HCV, HIV, HPV, HSV, JEV, SARS-CoV, RSV and influenza A virus, and directed searches of scholarly publisher's websites including ACS, Elsevier, Springer, Thieme, and Wiley. The compounds were classified on their structural characteristics as 1) arylnaphthalene lignans, 2) aryltetralin lignans, 3) dibenzylbutyrolactone lignans, 4) dibenzylbutane lignans, 5) tetrahydrofuranoid and tetrahydrofurofuranoid lignans, 6) benzofuran lignans, 7) neolignans, 8) dibenzocyclooctadiene lignans and homolignans, and 9) norlignans and other lignoids. Details on isolation and antiviral activities of the most active compounds within each class of lignan are discussed in detail, as are studies of synthetic lignans that provide structure-activity relationship information.

Anti-hepatitis B activities of Myanmar medicinal plants: a narrative review of current evidence

Hepatitis B is one of the major burdens for health services and is the leading cause of morbidity and mortality from cirrhosis of liver and hepatocellular carcinoma. Current treatment strategies using nucleos(t)ide analogue reverse-transcriptase inhibitors or interferons are targeted for the long-term suppression of hepatitis B DNA. However, functional cure of hepatitis B infection (HBsAg clearance) was difficult to attain with such treatments. Therefore, new treatment strategies or innovative treatments are urgently needed. The new treatments should focus on the potential therapeutic targets such as covalently closed circular DNA which may be important for the HBsAg clearance. Plant based medicines have been used in different traditional medicine practices and these natural products/compounds serve as a good source of information or clues for use in drug discovery and design. Many natural products were found to be effective against hepatitis B virus and some even have better therapeutic activities than currently used compounds. This review summarizes the current evidence of Myanmar medicinal plants in basic and clinical research which shows promising potential for the development of novel therapeutic agents for the treatment of hepatitis B.

Scale-up approach for supercritical fluid extraction with ethanol-water modified carbon dioxide on Phyllanthus niruri for safe enriched herbal extracts

Scaling-up supercritical fluid extraction (SFE) for the extraction of bioactive compounds from herbal plants is challenging, especially with the presence of alcohol-water as co-solvent. Hence, the main objective of this study is to validate the scale-up criteria of SFE process for Phyllanthus niruri (P. niruri), and analyse the extract safety and profitability process at the industrial scale. The study was performed by using supercritical carbon dioxide (SC-CO₂) with ethanol-water co-solvent at two operating conditions (L1: 200 bar, 60 °C and L2: 262 bar, 80 °C). The solvent-to-feed ratio (S/F) scale-up validation experiments were conducted at both operating conditions with feed mass capacity of 0.5 kg. The extraction yields and overall extraction curves obtained were almost similar to the predicted ones, with error of 5.13% and 14.2%, respectively. The safety of scale-up extract was evaluated by using a toxicity test against zebrafish embryo (FETT). The extract exhibited a low toxic effect with the LD₅₀ value of 505.71 µg/mL. The economic evaluation using a detailed profitability analysis showed that the SFE of P. niruri was an economically feasible process, as it disclosed the encouraging values of return on investment (ROI) and net present values (NPV) for all scale-up capacities.

Design, Synthesis and Bioactive Evaluation of Oxime Derivatives of Dehydrocholic Acid as Anti-Hepatitis B Virus Agents

Oxime derivatives of dehydrocholic acid and its esters were designed for anti-hepatitis B virus (HBV) drugs according to principles of assembling active chemical fragments. Twelve compounds were synthesized from dehydrocholic acid by esterification and oxime formation, and their anti-hepatitis B virus (HBV) activities were evaluated with HepG 2.2.15 cells. Results showed that 5 compounds exhibited more effective inhibition of HBeAg than positive control, among them 2b-3 and 2b-1 showed significant anti-HBV activities on inhibiting secretion of HBeAg (IC_{50 (2b-3)} = 49.39 ± 12.78 μM, SI _(2b-3) = 11.03; IC_{50 (2b-1)} = 96.64 ± 28.99 μM, SI _(2b-1) = 10.35) compared to the Entecavir (IC₅₀ = 161.24 μM, SI = 3.72). Molecular docking studies showed that most of these compounds interacted with protein residues of heparan sulfate proteoglycan (HSPG) in host hepatocyte and bile acid receptor.

In-vitro propagation, callus culture and bioactive lignan production in Phyllanthus tenellus Roxb: a new source of phyllanthin, hypophyllanthin and phyltetralin

This is the first report on identification and quantification of important hepatoprotective and anticancer polyphenolic lignans such as phyllanthin (PH), hypophyllanthin (HPH), niranthin (NH) and phyltetralin (PT) in natural plant and in vitro cultures of Phyllanthus tenellus Roxb. The identification of lignans was carried out by Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS) and quantified using High-Performance Liquid Chromatography (HPLC). In addition, an efficient protocol has been developed for multiple shoot induction in nodal explants of in vitro derived shoots of P. tenellus. Maximum number of shoot regeneration (7.83 ± 0.15) was achieved on medium incorporated with 1.0 mg/l 6-Benzylaminopurine (BAP). The medium containing Indole-3-acetic acid (IAA) 2 mg/l was superior for induction of rooting in in vitro raised shoots. The plantlets were acclimatized to the field condition with 100% survival. The quantitative HPLC analysis showed that the lignan content was variable with the auxins and cytokinins incorporated in the medium. The lignan content was higher in callus grown on Murashige and Skoog (MS) medium + 2.0 mg/l Naphthaleneacetic acid (NAA). The reported protocol can be used for mass propagation and application of biotechnological approaches for improvement of P. tenellus. The results indicate intriguing possibilities for the utilization of P. tenellus plant parts as an alternative source and of callus culture to scale up bioactive lignan production for pharmaceutical applications.

Antiviral Evaluation of Herbal Drugs

The viral infection and resistance to the existing antiviral drugs are alarming, which is a serious public health concern. Medicinal plants are valuable resources for treatment of viral infections and can be used for the management of infections like herpes simplex virus (HSV), human immunodeficiency virus (HIV), influenza, etc. The antiviral screening of plant extracts should be highly selective, specific, and sensitive for bioactivity guided isolation of the active compounds from the plant extracts. The antiviral screening system should be validated for accuracy, reproducibility, simplicity, and cost effectiveness. This chapter highlights on various aspects for screening and evaluation of antiviral natural components including factors affecting antiviral in vivo studies, host cells, organisms, and culture media followed by different virus-specific assays for antiviral screening of natural products.

Discovery of Oxime Ethers as Hepatitis B Virus (HBV) Inhibitors by Docking, Screening and In Vitro Investigation

A series of oxime ethers with C₆-C₄ fragment was designed and virtually bioactively screened by docking with a target, then provided by a Friedel–Crafts reaction, esterification (or amidation), and oximation from p-substituted phenyl derivatives (Methylbenzene, Methoxybenzene, Chlorobenzene). Anti-hepatitis B virus (HBV) activities of all synthesized compounds were evaluated with HepG2.2.15 cells in vitro. Results showed that most of compounds exhibited low cytotoxicity on HepG2.2.15 cells and significant inhibition on the secretion of HBsAg and HBeAg. Among them, compound 5c-1 showed the most potent activity on inhibiting HBsAg secretion (IC₅₀ = 39.93 μM, SI = 28.51). Results of the bioactive screening showed that stronger the compounds bound to target human leukocyte antigen A protein in docking, the more active they were in anti-HBV activities in vitro.

Development of a UHPLC-MS/MS method for the quantitation of bioactive compounds in Phyllanthus species and its herbal formulations

Phyllanthus species are extensively used in traditional medicines for the treatment of hepatic diseases due to their bioactive hypophyllanthin and phyllanthin. This work describes the development and validation of an ultra high performance liquid chromatography with tandem mass spectrometry method in polarity switching multiple reaction monitoring mode for the simultaneous detection and quantitation of 23 compounds using ultra-performance liquid chromatography coupled with electrospray-hybrid triple quadrupole-linear ion trap mass spectrometer. The validated parameters showed good linearity (R²  ≥ 0.996), limit of detection (0.05-1.62 ng/mL), limit of quantitation (0.15-4.95 ng/mL), precisions (intra-day: RSD ≤ 2.11%), (inter-day: RSD ≤ 2.91%), stability (RSD ≤ 2.56%) and overall recovery (98.22-104.48%; RSD ≤ 2.93%). The validated method was successfully applied in ethanolic extracts of P. amarus, P. niruri, P. emblica, P. fraternus, fractions of P. amarus and their herbal formulations for quantitation. The maximum content of hypophyllanthin (29.40 mg/g) and phyllanthin (56.60 mg/g) was detected in ethyl acetate fraction of P. amarus. The total content of 23 compounds was abundant in the ethanolic extract of P. emblica fruit. Principal component analysis was used to differentiate the selected Phyllanthus species and their herbal formulations. The results indicated that the present method could be used for quality control of Phyllanthus species and its herbal formulations.

The pharmacological potential of Phyllanthus niruri

INTRODUCTION

Phyllanthus niruri is a traditional shrub of the genus Phyllanthaceae with long-standing Ayurvedic, Chinese and Malay ethnomedical records. Preliminary studies from cell and animal model have provided valuable scientific evidence for its use.

AIM

This review aims to summarize selected scientific evidence on the pharmacological properties of P. niruri over the past 35 years while identifying potential areas of further development of this herb as an economical adjunct.

METHODS

The review covers literature pertaining to the evidence base therapeutic potential of P. niruri spanning from 1980 to 2015 available on PubMed.

RESULTS

Evidence suggests that the extracts of P. niruri possess hepatoprotective, antiviral, antibacterial, hypolipidaemic, hypoglycaemic, analgesic, anti-inflammatory, cardioprotective, anti-urolithiatic and antihyperuricaemic properties due its novel bioactive compounds.

CONCLUSION

Scientific evidence suggests that there is strong pharmacological potential in developing P. niruri as a drug to be used in liver disorders and in antiviral therapy. Despites this, large-scale heterogeneity in study protocol and unstandardized reporting standards limit the ability for valuable comparison and may mask the ability to replicate these studies. Thus interpretation of findings should be performed with caution and further studies should be performed in line with best practices. More cheminformatics, toxicological and mechanistic studies would aid the progress to clinical trial studies.

The Genus Phyllanthus: An Ethnopharmacological, Phytochemical, and Pharmacological Review

The plants of the genus Phyllanthus (Euphorbiaceae) have been used as traditional medicinal materials for a long time in China, India, Brazil, and the Southeast Asian countries. They can be used for the treatment of digestive disease, jaundice, and renal calculus. This review discusses the ethnopharmacological, phytochemical, and pharmacological studies of Phyllanthus over the past few decades. More than 510 compounds have been isolated, the majority of which are lignins, triterpenoids, flavonoids, and tannins. The researches of their remarkable antiviral, antioxidant, antidiabetic, and anticancer activities have become hot topics. More pharmacological screenings and phytochemical investigations are required to support the traditional uses and develop leading compounds.

HPLC–MS/MS method for the determination of four lignans from Phyllanthus urinaria L. in rat plasma and its application

Background: Phyllanthus urinaria L. showed significant hepatoprotective and anti-HBV activities. A sensitive and rapid HPLC–MS/MS method has been developed and validated for the simultaneous determination of hypophyllanthin, phyllanthin, nirtetralin and niranthin from Phyllanthus urinaria L. in rat plasma. The analytes were extracted from rat plasma with n-hexane/isopropanol and diazepam was used as the internal standard. Results: The calibration curves were linear (r > 0.9971) over a concentration range of 2–1000 ng/ml for hypophyllanthin and nirtetralin, and 1–1000 ng/ml for phyllanthin and niranthin. The precision, accuracy, recovery and stability were deemed acceptable. Conclusion: The HPLC–MS/MS method was successfully applied to a PK study of the four lignans in rats after oral administration of Phyllanthus urinaria L. extract.

Strategy to rapidly discriminate trace isomeric lignan compounds from Gymnotheca chinensis by probe electrospray ionization tandem mass spectrometry

Probe electrospray ionization (PESI) is a recently developed ionization technique based on electrospray ionization (ESI) that generates electrospray from the tip of a solid needle. High tolerance to salts, requirements of a trace amount of sample and direct ambient sampling- are major advantages of PESI compared with conventional ESI. In this report, three pairs of isomeric lignans bearing tetra-hydrofuran with variable conformations from Gymnotheca chinensis were investigated by probe electrospray tandem mass spectrometry (PESI-MS/MS) in the positive ion mode. The diagnostic characteristics of these compounds were obtained and the isomers could be successfully distinguished by comparison with their breakdown curves, even though the isomers differed only in the conformation of some groups of the isomer pairs. This report provides a rapid and reliable method for the identification of trace amounts of isomeric lignans by PESI-MS/MS. Furthermore, application of PESI and breakdown curves should have value in mass spectrometry studies of isomeric natural products compounds.

Validation of Antiviral Potential of Herbal Ethnomedicine

Natural products are the basis of treatment since the dawn of human civilization, and modern medicine has gradually developed, over the years, by scientific and observational efforts from traditional medicine. Today most of the synthetic drugs showed adverse and unacceptable side effects, however, impressive bioactivities with reduced toxicities were reported for many botanicals against several chronic or difficult-to-treat diseases. A whole range of viral diseases including human immunodeficiency virus/acquired immunodeficiency syndrome, severe acute respiratory syndrome, Rabies, Dengue, and Herpes need effective drugs. Considerable research has been carried out on the pharmacognosy, chemistry, pharmacology, and therapeutics of traditional medicines of diverse cultures, and many pharmaceutical companies have renewed their strategies for antiviral drug development where no effective drugs or vaccine exist. Thus, phytochemicals with antiviral potentials need to be studied in depth with standardization, chemical isolation, effectivity, molecular mechanism, along with in vivo toxicity and efficacy to reduce cost and time. This review will portray the scientific approaches and methodologies used for the development of antiviral leads from traditional medicines against selected genetically and functionally diverse viral infections.

In vitro and in vivo anti-hepatitis B virus activities of the lignan nirtetralin B isolated from Phyllanthus niruri L

ETHNOPHARMACOLOGICAL RELEVANCE

Nirtetralin B, a new lignan first reported by our team, is isolated from Phyllanthus niruri L. This plant has long been used in folk medicine for liver protection and antihepatitis B in many Asian countries. This study was designed to evaluate the anti-hepatitis B virus activity of nirtetralin B using HepG2.2.15 cells and duck hepatitis B virus (DHBV) infected ducks as in vitro and in vivo models.

MATERIALS AND METHODS

Nirtetralin B was isolated from Phyllanthus niruri L. (Euphorbiaceae) by extraction and chromatographic procedures and the anti-hepatitis B virus activity was evaluated both in vitro and in vivo. The human HBV-transfected liver cell line HepG2.2.15 was used in vitro assay. And the in vivo anti-hepatitis B virus activity was evaluated on the expression of HBV replication, HBsAg, HBeAg, ALT and AST on day 0, 7, 14, 17 after nirtetralin B was dosed intragastricly (i.g.) once a day for 14 days at the dosages of 25, 50 and 100mg/kg/day in the duck hepatitis B virus (DHBV) infected ducks.

RESULTS

In the human HBV-transfected liver cell line HepG2.2.15, nirtetralin B effectively suppressed the secretion of the HBV antigens in a dose-dependent manner with IC50 values for HBsAg of 17.4μM, IC50 values for HBeAg of 63.9μM. In DHBV-infected ducklings, nirtetralin B significantly reduced the serum DHBV DNA, HBsAg, HBeAg, ALT and AST. And analysis of the liver pathological changes confirmed the hepatoprotective effect of nirtetralin B.

CONCLUSION

The experimental data demonstrated that nirtetralin B exhibits anti-hepatitis B virus activity both in vitro and in vivo.

In vitro and in vivo anti-hepatitis B virus activities of the lignan niranthin isolated from Phyllanthus niruri L

ETHNOPHARMACOLOGICAL RELEVANCE

Niranthin is a lignan isolated from Phyllanthus niruri L. This plant has long been used in folk medicine for liver protection and antihepatitis B in many Asian countries. This study was designed to evaluate the anti-hepatitis B virus activity of niranthin using HepG2.2.15 cells and duck hepatitis B virus (DHBV) infected ducks as in vitro and in vivo models.

MATERIALS AND METHODS

Niranthin was isolated from Phyllanthus niruri L. (Euphorbiaceae) by extraction and chromatographic procedures and the anti-hepatitis B virus activity was evaluated both in vitro and in vivo. The human HBV-transfected liver cell line HepG2.2.15 was used in vitro assay. And the in vivo anti-hepatitis B virus activity was evaluated on the expression of HBV replication, HBsAg, HBeAg, ALT and AST on day 0, 7, 14, 17 after niranthin was dosed intragastricly (i.g.) once a day for 14 days at the dosages of 25, 50 and 100 mg/kg/day in the duck hepatitis B virus (DHBV) infected ducks.

RESULTS

In the human HBV-transfected liver cell line HepG2.2.15, the secretion of HBsAg and HBeAg were significantly decreased after treatment with niranthin for 144 h, with IC50 values for HBsAg of 15.6 µM, IC50 values for HBeAg of 25.1 µM. In DHBV-infected ducklings, niranthin significantly reduced the serum DHBV DNA, HBsAg, HBeAg, ALT and AST. Furthermore, analysis of the liver pathological changes confirmed the hepatoprotective effect of niranthin.

CONCLUSION

The experimental data demonstrated that niranthin exhibits anti-hepatitis B virus activity both in vitro and in vivo.

Evaluation of (anti)genotoxic activities of Phyllanthus niruri L. in rat bone marrow using the micronucleus test

Phyllanthus niruri L. (Euphorbiaceae), known as "quebra-pedra" (Portuguese for "stonebreaker"), is an herb used for kidney disorders. In light of its frequent use by the population, the present study aimed to investigate the genotoxic, antigenotoxic and cytotoxic activities of a standardized P. niruri extract in bone marrow rats. Three groups of 12 animals were treated daily by gavage over a period of 30 days, with 50, 150 or 250 mg/kg of P. niruri extract aqueous solution. The control group (n = 12) received tap water. At the end of treatment (day 31), groups were divided into two minor subgroups (n=6/group) and received cyclophosphamide (50 mg/kg, i.p.) or saline 0.9% (i.p.). After 24 hours, we evaluated the frequency of micronucleated polychromatic erythrocytes for each animal (MNPCE) at 1000 PCE. Cytotoxicity was evaluated with the PCE/NCE ratio (NEC = normochromatic erythrocytes). General toxicity was assessed during treatment using the parameters of body weight gain, ration and water consumption. The dry extract did not provoke changes in body weight, weight gain, ration and water intake or changes in the frequency of MNPCE or cytotoxicity in bone marrow. We propose that the P. niruri extract used here showed no genotoxic, antigenotoxic and cytotoxic activities under the experimental conditions.

The lignan (-)-cubebin inhibits vascular contraction and induces relaxation via nitric oxide activation in isolated rat aorta

Cubebin, the most abundant lignan in Piper cubeba, has been described as having several effects as trypanocidal, antimycobacterial, antispasmodic, antimicrobial, anti-inflammatory, and analgesic. This study investigated the vasorelaxant effect produced by (-)-cubebin in isolated rat aortic rings pre-contracted with phenylephrine (Phe), and the possible mechanism involved in this event was evaluated. Endothelium-dependent relaxation was evoked by acetylcholine and (-)-cubebin in intact aortic rings, while endothelium-independent vasorelaxation was elicited by sodium nitroprusside and (-)-cubebin in denuded rings. Cumulative concentration-response curves for Phe (10(-10) -10(-5)  M) were determined for endothelium-intact and endothelium-denuded aortic rings in either the presence or absence of (-)-cubebin. Dose-response curves were also constructed for pre-incubation of vascular rings with Nω-nitro-L-arginine methyl ester (L-NAME) (a non-specific nitric oxide synthase inhibitor), indomethacin (an unspecific cyclooxygenase inhibitor), and 1H-[1,2,4] oxadiazolo [4,3-a]quinoxalin-1-one (ODQ) (a guanylyl cyclase inhibitor). (-)-Cubebin was found to exert a vasorelaxant effect irrespective of the presence of endothelium, which was abolished by pretreatment with L-NAME and ODQ, but not with indomethacin. In addition, (-)-cubebin was able to reduce Phe contraction in the case of intact rings. These results suggest that (-)-cubebin promotes vasorelaxation via NO/cGMP pathway in rat aorta, without prostacyclin involvement.