Flavokawain B, the hepatotoxic constituent from kava root, induces GSH-sensitive oxidative stress through modulation of IKK/NF-kappaB and MAPK signaling pathways

A Label-Free Colorimetric Aptasensor for Flavokavain B Detection

Flavokavain B (FKB), a hepatotoxic chalcone from Piper methysticum (kava), has raised safety concerns due to its role in disrupting redox homeostasis and inducing apoptosis in hepatocytes. Conventional chromatographic methods for FKB detection, while sensitive, are costly and impractical for field applications. In this work, DNA aptamers were selected using the library-immobilized method and high-throughput sequencing. Three families of aptamers were obtained, and the best one named FKB-S showed a dissociation constant (KD) of 280 nM using microscale thermophoresis. To demonstrate its practical utility, a rapid and label-free colorimetric aptasensor was developed based on aptamer-induced gold nanoparticle aggregation. This assay achieved a detection limit of 150 nM (43.46 ng/mL) and provided results within 10 min. Compared to traditional chromatographic methods, the aptasensor offers a simple, cost-effective, and equipment-free approach for on-site FKB detection, making it a promising tool for the quality control and safety monitoring of kava-based products in diverse environments.

Toxicity Potential of Nutraceuticals

During the past few decades and especially during and after the COVID-19 pandemic, the use of nutraceuticals has become increasingly popular in both humans and animals due to their easy access, cost-effectiveness, and tolerability with a wide margin of safety. While some nutraceuticals are safe, others have an inherent toxic potential. For a large number of nutraceuticals, no toxicity/safety data are available due to a lack of pharmacological/toxicological studies. The safety of some nutraceuticals can be compromised via contamination with toxic plants, metals, mycotoxins, pesticides, fertilizers, drugs of abuse, etc. Knowledge of pharmacokinetic/toxicokinetic studies and biomarkers of exposure, effect, and susceptibility appears to play a pivotal role in the safety and toxicity assessment of nutraceuticals. Interaction studies are essential to determine efficacy, safety, and toxicity when nutraceuticals and therapeutic drugs are used concomitantly or when polypharmacy is involved. This chapter describes various aspects of nutraceuticals, particularly their toxic potential, and the factors that influence their safety.

The potential of AB-free kava in enabling tobacco cessation via management of abstinence-related stress and insomnia: study protocol for a randomized clinical trial

BACKGROUND

As the primary cause of various preventable illnesses, smoking results in approximately five million premature deaths each year in the US and a multitude of adults living with serious illness. The majority of smokers know the health risks associated with smoking and intend to quit. However, quitting is very difficult partly because of insomnia and stress associated with it. Current tobacco cessation medications are not designed to address these problems, which may have contributed to their limited success in enabling cessation. Novel interventions are thus urgently needed to enhance success rates in tobacco cessation. Based on its historical usage and our preliminary data, kava is such a candidate. Kava, customarily enjoyed by South Pacific Islanders, is known for its relaxing effects, stress-relieving properties, and ability to enhance sleep. In the US, it is marketed and distributed as a dietary supplement due to its recognized calming properties. A pilot trial was performed among active smokers with a one-week ingestion of a kava supplement. The results for the first-time revealed kava's potential in enabling tobacco cessation with effects on a panel of biological signatures. The primary goal of this trial is to replicate kava's effects on the biological signatures of tobacco use, stress, and sleep in addition to its compliance and safety among those who smoke.

METHODS

A double-blind randomized placebo controlled two-arm trial will enroll 76 smokers with intention to quit, who will consume AB-free kava at a dietary supplement dose or placebo, 3 times per day for 4 weeks with two follow-ups.

DISCUSSION

The study will (1) monitor the adherence to and safety of AB-free kava consumption among smokers and evaluate changes in smoking habits, and (2) quantify a panel of non-invasive translatable biomarkers to objectively evaluate AB-free kava's holistic effects on biological signatures associated with tobacco use, stress, and sleep. We hypothesize that AB-free kava is a novel and promising intervention to facilitate tobacco cessation via its holistic effects associated with managing stress and insomnia during abstinence. If the results from this study support our hypothesis, kava could emerge as an affordable and accessible dietary supplement candidate for tobacco cessation.

TRIAL REGISTRATION

registered on 04/14/2023 in ClinicalTrials.gov with the identifier NCT05814055.

Flavokavains A- and B-Free Kava Enhances Resilience against the Adverse Health Effects of Tobacco Smoke in Mice

Tobacco smoke remains a serious global issue, resulting in serious health complications, contributing to the onset of numerous preventive diseases and imposing significant health burdens. Despite regulatory policies and cessation measures aimed at curbing its usage, novel interventions are urgently needed for effective damage reduction. Our preclinical and pilot clinical studies showed that AB-free kava has the potential to reduce tobacco-smoking-induced lung cancer risk, mitigate tobacco dependence, and reduce tobacco use. To understand the scope of its benefits in damage reduction and potential limitations, this study evaluated the effects of AB-free kava on a panel of health indicators in mice exposed to 2-4 weeks of daily tobacco smoke exposure. Our assessments included global transcriptional profiling of the lung and liver tissues, analysis of lung inflammation, evaluation of lung function, exploration of tobacco nicotine withdrawal, and characterization of the causal protein kinase A (PKA) signaling pathway. As expected, tobacco smoke exposure perturbed a wide range of biological processes and compromised multiple functions in mice. Remarkably, AB-free kava demonstrated the ability to globally mitigate tobacco smoke-induced deficits at the molecular and functional levels with promising safety profiles, offering AB-free kava unique promise to mitigate tobacco smoke-related health damages. Further preclinical evaluations are warranted to fully harness the potential of AB-free kava in combating tobacco smoke-related harms in the preparation of its clinical translation.

AB-free kava enhances resilience against the adverse health effects of tobacco smoke in mice

Tobacco smoke remains a serious global issue, resulting in serious health complications, contributing to the onsets of numerous preventive diseases, and imposing significant financial burdens. Despite regulatory policies and cessation measures aimed at curbing its usage, novel interventions are urgently needed for effective damage reduction. Our preclinical and pilot clinical studies showed that AB-free kava has the potential to reduce tobacco smoke-induced lung cancer risk, mitigate tobacco dependence, and reduce tobacco use. To understand the scope of its benefits in damage reduction and potential limitations, this study evaluated the effects of AB-free kava on a panel of health indicators in mice exposed to 2 - 4 weeks of daily tobacco smoke exposure. Our comprehensive assessments included global transcriptional profiling of the lung and liver tissues, analysis of lung inflammation, evaluation of lung function, exploration of tobacco nicotine withdrawal, and characterization of the causal PKA signaling pathway. As expected, Tobacco smoke exposure perturbed a wide range of biological processes and compromised multiple functions in mice. Remarkably, AB-free kava demonstrated the ability to globally mitigate tobacco smoke-induced deficits at the molecular and functional levels with promising safety profiles, offering a unique promise to mitigate tobacco smoke-related health damages. Further pre-clinical evaluation and clinical translation are warranted to fully harness the potential of AB-free kava in combating tobacco smoke-related harms.

Photosynthesis-related physiology and metabolomics responses of Polygonum lapathifolium in contrasting manganese environments

Manganese (Mn) plays an essential role in plant growth; however, excessive Mn is toxic to plants. Polygonum lapathifolium Linn. was tested as a novel Mn-hyperaccumulating species in our previous study, but the underlying mechanisms of this hyperaccumulation are poorly understood. A hydroponic experiment with (8mmolL-1 ) and without additional Mn (CK) was established to explore the possible mechanisms through the effects on photosynthesis-related physiological characteristics and metabolomics. The results showed that additional Mn increased plant biomass, photosynthesis, and stomatal conductance related to increases in the effective photochemical quantum yield of photosystem II and relative electron transport rate (P <0.05). The results from liquid chromatography-mass spectrometry revealed 56 metabolites differentially accumulated between the plants composing these two groups. Metabolites were enriched in 20 metabolic pathways at three levels (environmental information processing, genetic information processing, and metabolism), of which five metabolic pathways were associated with significant or extremely significant changes (P <0.05). These five enriched pathways were ABC transporters (environmental information processing), aminoacyl-tRNA biosynthesis (genetic information processing), biosynthesis of amino acids , d -arginine and d -ornithine metabolism , and arginine biosynthesis (metabolism). Flavonoids may play a key role in Mn tolerance, as they accumulated more than 490-fold, and the relationship between flavonoids and Mn tolerance needs to be studied in the future.

Characterization of Different Forms of Kava (Piper methysticum) Products by UPLC-MS/MS

There are several forms of kava (Piper methysticum) products available for human consumption, and many factors are known to influence their chemical compositions and therefore their pharmacological properties. Because of the increased popularity of kava intake, a rigorous characterization of their content diversity is prerequisite, particularly due to its known potential to cause hepatotoxicity. To understand the composition diversity of kavalactones and flavokavains in commercial kava products, we developed a UPLC-MS/MS-based analytical method for the quantification of six kavalactones (kavain, dihydrokavain, methysticin, dihydromethysticin, yangonin and desmethoxyyangonin) and two flavokavains (flavokavains A and B) and analyzed their contents in 28 different kava products in the form of capsules, tinctures, traditional aqueous suspensions and dried powders. Our results demonstrated a great variation in terms of the total and relative abundance of the analyzed kavalactones and flavokavains among the analyzed kava preparations. More importantly, the kavalactone abundance in the product label could differ up to 90% from our experimental measurements. Therefore, more rigorous and comprehensive quality control of kava products is required with respect to the content of individual kavalactones and flavokavains. Accurate content information is essential to understand the pharmacological properties and safety of different kava products.

Clinical pharmacokinetics of kavalactones after oral dosing of standardized kava extract in healthy volunteers

ETHNOPHARMACOLOGICAL RELEVANCE

Piper methysticum G. Forst. (Piperaceae), commonly known as kava, has been used as a traditional beverage for centuries for its relaxing properties. Kavalactones are considered to be the major constituents responsible for kava's beneficial effects. Despite the extensive use of kava, clinical pharmacokinetic data is not available in the literature; therefore, the findings of this study will be critical for the dosage calculations for future clinical evaluation of kava.

AIM OF THE STUDY

The aim of the current study is to examine the clinical pharmacokinetics of six major kavalactones following oral dosing of flavokavain A/B-free standardized kava extract capsules in healthy volunteers using two dosage regimens.

MATERIALS AND METHODS

A sensitive, reliable, and specific ultra-high pressure liquid chromatography-mass spectrometry (UPLC-MS/MS) method was developed and validated for the simultaneous quantification of six major kavalactones (kavain, dihydrokavain, methysticin, dihydromethysticin, yangonin, and desmethoxyyangonin) and two flavokavains (A and B) in human plasma. Pharmacokinetic profiles were assessed in ten healthy volunteers after oral doses of standardized kava product, and plasma samples were analyzed for six kavalactones and two flavokavains using the validated UPLC-MS/MS method. Concentration-time data was subjected to pharmacokinetic analysis.

RESULTS

The systemic exposure of the kavalactones was found to be in the following order: dihydrokavain > dihydromethysticin > kavain > methysticin > yangonin. Desmethoxyyangonin was quantifiable only at a couple of time points, while flavokavain A and flavokavain B were not present in any of the plasma samples. Fast absorption of five kavalactones was observed with time to reach the maximum plasma concentration of 1-3 h. A dose proportionality in pharmacokinetics was established from 75 to 225 mg of kavalactone doses. In the multiple-dose study, a significant reduction in the extent of absorption of kavalactones with food was observed.

CONCLUSION

Single and multiple-dose clinical pharmacokinetic studies for kava were performed in healthy volunteers, and higher exposure to the kavalactones was observed after single-dosing (225 mg), while a longer duration of exposure was observed after three times a day (3 x 75 mg) dosing.

An Updated Review on the Psychoactive, Toxic and Anticancer Properties of Kava

Kava (Piper methysticum) has been widely consumed for many years in the South Pacific Islands and displays psychoactive properties, especially soothing and calming effects. This plant has been used in Western countries as a natural anxiolytic in recent decades. Kava has also been used to treat symptoms associated with depression, menopause, insomnia, and convulsions, among others. Along with its putative beneficial health effects, kava has been associated with liver injury and other toxic effects, including skin toxicity in heavy consumers, possibly related to its metabolic profile or interference in the metabolism of other xenobiotics. Kava extracts and kavalactones generally displayed negative results in genetic toxicology assays although there is sufficient evidence for carcinogenicity in experimental animals, most likely through a non-genotoxic mode of action. Nevertheless, the chemotherapeutic/chemopreventive potential of kava against cancer has also been suggested. Both in vitro and in vivo studies have evaluated the effects of flavokavains, kavalactones and/or kava extracts in different cancer models, showing the induction of apoptosis, cell cycle arrest and other antiproliferative effects in several types of cancer, including breast, prostate, bladder, and lung. Overall, in this scoping review, several aspects of kava efficacy and safety are discussed and some pertinent issues related to kava consumption are identified.

Methysticin Acts as a Mechanism-Based Inactivator of Cytochrome P450 2C9

Methysticin is one of the naturally occurring bioactive constituents extracted from Piper methysticum Forst. In the present study, we intended to investigate the inhibitory effect of methysticin on cytochrome P450 (P450) enzymes. Methysticin exhibited time-, concentration-, and NADPH-dependent inhibition on CYP2C9 using diclofenac as a probe substrate. Approximately 85% of CYP2C9 activity was inhibited by methysticin at 50 μM after a 30 min preincubation with human liver microsomes in the presence of NADPH. The kinetic parameters K_I, k_inact, and t_1/2,inact were 13.32 ± 1.35 μM, 0.054 ± 0.005 min^-1, and 12.83 ± 3.23 min, respectively. Sulfaphenazole (competitive inhibitor of CYP2C9) displayed a significant protective effect on methysticin-induced CYP2C9 inactivation. However, the inclusion of catalase/superoxide dismutase or glutathione (GSH) showed no such protection. A carbene intermediate was postulated to be involved in methysticin-induced CYP2C9 inactivation as K₃Fe(CN)₆ recovered 14.96% of CYP2C9 activity. A methysticin-derived ortho-quinone intermediate dependent on NADPH was trapped by GSH, and this intermediate was believed to be involved in CYP2C9 inactivation. CYP1A2, 2C9, and 3A4 were the major enzymes responsible for methysticin bioactivation. Taken together, the present work demonstrated that methysticin was a mechanism-based inactivator of CYP2C9. Both ortho-quinone and carbene intermediates appeared to be involved in the inactivation of CYP2C9 induced by methysticin.

Yangonin treats inflammatory osteoporosis by inhibiting the secretion of inflammatory factors and RANKL expression

OBJECTIVES

As the main cause of osteoporosis, abnormal activity of osteoclasts could disrupt the balance between bone resorption and formation. Moreover, up-regulation of nuclear factor-kappa ligand (RANKL) expression by chronic inflammation-mediated inflammatory factors might contribute to the differentiation of osteoclast precursor cells. Therefore, an anti-inflammatory agent named yangonin was presented for inhibiting osteoclast and relieving inflammatory osteoporosis through down-regulating inflammatory factors.

METHODS

We established a model of macrophage inflammation and then verified the anti-inflammatory effect of yangonin. The inhibitory effect of yangonin on osteoclasts was detected by tartrate-resistant acid phosphatase (TRAP) staining, Western blotting and quantitative real-time PCR (qRT-PCR). Finally, micro-CT, TRAP and hematoxylin-eosin (HE) staining were used to show the effect of yangonin on inflammatory osteoporosis in vivo.

RESULTS

Our results suggested that yangonin was able to reduce the secretion of inflammatory factors, down-regulate osteoclast-related genes such as TRAP, RANKL, cathepsin K (CTSK) and nuclear factor-activated T-cell 1 (NFATc1). Furthermore, it was demonstrated that yangonin could suppress the function of inflammatory cytokines in osteoclast differentiation and reporting, wherein NF-κB, AKT and downstream c-Fos/NFATc1 signaling pathways were involved. In an in vivo study, we implied that yangonin has a relieving effect on inflammatory osteoporosis.

CONCLUSION

Our research shows that yangonin down-regulates inflammatory factors and inhibits the bone-breaking effect of inflammation through NF-κB, AKT and downstream c-Fos/NFATc1 signaling pathways to achieve the purpose of treating inflammatory osteoporosis.

Biological Activity, Hepatotoxicity, and Structure-Activity Relationship of Kavalactones and Flavokavins, the Two Main Bioactive Components in Kava (Piper methysticum)

Kava (Piper methysticum Forst) is a popular and favorable edible medicinal herb which was traditionally used to prepare a nonfermented beverage with relaxant beneficial for both social and recreational purposes. Numerous studies conducted on kava have confirmed the presence of kavalactones and flavokawains, two major groups of bioactive ingredients, in this miraculous natural plant. Expectedly, both kavalactone and flavokawain components exhibited potent antianxiety and anticancer activities, and their structure-activity relationships were also revealed. However, dozens of clinical data revealed the hepatotoxicity effect which is indirectly or directly associated with kava consumption, and most of the evidence currently seems to point the compounds of flavokawains in kava were responsible. Therefore, our aim is to conduct a systematic review of kavalactones and flavokawains in kava including their biological activities, structure-activity relationships, and toxicities, and as a result of our systematic investigations, suggestions on kava and its compounds are supplied for future research.

Kava as a Clinical Nutrient: Promises and Challenges

Kava beverages are typically prepared from the root of Piper methysticum. They have been consumed among Pacific Islanders for centuries. Kava extract preparations were once used as herbal drugs to treat anxiety in Europe. Kava is also marketed as a dietary supplement in the U.S. and is gaining popularity as a recreational drink in Western countries. Recent studies suggest that kava and its key phytochemicals have anti-inflammatory and anticancer effects, in addition to the well-documented neurological benefits. While its beneficial effects are widely recognized, rare hepatotoxicity had been associated with use of certain kava preparations, but there are no validations nor consistent mechanisms. Major challenges lie in the diversity of kava products and the lack of standardization, which has produced an unmet need for quality initiatives. This review aims to provide the scientific community and consumers, as well as regulatory agencies, with a broad overview on kava use and its related research. We first provide a historical background for its different uses and then discuss the current state of the research, including its chemical composition, possible mechanisms of action, and its therapeutic potential in treating inflammatory and neurological conditions, as well as cancer. We then discuss the challenges associated with kava use and research, focusing on the need for the detailed characterization of kava components and associated risks such as its reported hepatotoxicity. Lastly, given its growing popularity in clinical and recreational use, we emphasize the urgent need for quality control and quality assurance of kava products, pharmacokinetics, absorption, distribution, metabolism, excretion, and foundational pharmacology. These are essential in order to inform research into the molecular targets, cellular mechanisms, and creative use of early stage human clinical trials for designer kava modalities to inform and guide the design and execution of future randomized placebo controlled trials to maximize kava's clinical efficacy and to minimize its risks.

The Impact of One-week Dietary Supplementation with Kava on Biomarkers of Tobacco Use and Nitrosamine-based Carcinogenesis Risk among Active Smokers

Tobacco smoking is the primary risk factor for lung cancer, driven by the addictive nature of nicotine and the indisputable carcinogenicity of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) as well as other compounds. The integration of lung cancer chemoprevention with smoking cessation is one potential approach to reduce this risk and mitigate lung cancer mortality. Experimental data from our group suggest that kava, commonly consumed in the South Pacific Islands as a beverage to promote relaxation, may reduce lung cancer risk by enhancing NNK detoxification and reducing NNK-derived DNA damage. Building upon these observations, we conducted a pilot clinical trial to evaluate the effects of a 7-day course of kava on NNK metabolism in active smokers. The primary objective was to compare urinary total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL plus its glucuronides, major metabolites of NNK) before and after kava administration as an indicator of NNK detoxification. Secondary objectives included determining kava's safety, its effects on DNA damage, tobacco use, and cortisol (a biomarker of stress). Kava increased urinary excretion of total NNAL and reduced urinary 3-methyladenine in participants, suggestive of its ability to reduce the carcinogenicity of NNK. Kava also reduced urinary total nicotine equivalents, indicative of its potential to facilitate tobacco cessation. Plasma cortisol and urinary total cortisol equivalents were reduced upon kava use, which may contribute to reductions in tobacco use. These results demonstrate the potential of kava intake to reduce lung cancer risk among smokers.

Herbal Active Ingredients: An Emerging Potential for the Prevention and Treatment of Papillary Thyroid Carcinoma

Papillary thyroid carcinoma (PTC) is the most common subtype of differentiated thyroid cancers in Asian coastal cities, where the patients have increased risk of potentially high or excessive iodine intake. Given the high metastasis and recurrence of patients with BRAF^V600E mutation, the mortality rate of thyroid cancer has recently shown an upward trend. A variety of therapies, including surgery, radiotherapy, and chemotherapy, have been used to treat thyroid cancer, but these therapies still have limitations, including postoperative complications, drug resistance, poor efficacy, or serious side effects. Recent studies have shown the potential of active ingredients derived from herbal medicine in inhibiting PTC via various cell signaling pathways. Some plant-derived compounds, such as apigenin, genistein, and curcumin, are also known to prevent and treat PTC. This article summarizes the recent advances in the structure-functional impact of anti-PTC active ingredients and their effects on PTC cells and tumor microenvironments with an emphasis on their challenges from basic research to clinical practice.

DARK Classics in Chemical Neuroscience: Kava

Kava (kava kava, Piper methysticum) is a common drug-containing plant in the Pacific islands. Kavalactones, its psychoactive compounds, exert potent central nervous system (CNS) action clinically and in animal models. However, the exact pharmacological profiles and mechanisms of action of kava on the brain and behavior remain poorly understood. Here, we discuss clinical and experimental data on kava psychopharmacology and summarize chemistry and synthesis of kavalactones. We also review its societal impact, drug use and abuse potential, and future perspectives on translational kava research.

Rapid detection and validated quantification of psychoactive compounds in complex plant matrices by direct analysis in real time-high resolution mass spectrometry - Application to "Kava" psychoactive pepper products

RATIONALE

Classified by the UNODC as a top 20 plant of concern, Piper methysticum (also known as Kava) is being increasingly abused recreationally for its mind-altering effects. It is of significant forensic relevance to establish methods to rapidly identifyand quantify psychoactive compounds, especially those yet to be scheduled ascontrolled substances and which have exhibited various noteworthy health concerns.

METHODS

Direct analysis in real time high-resolution mass spectrometry (DART-HRMS) demonstrated the ability to detect a range of kavalactones in Pipermethysticum derived products and plant material with no sample preparation. Inaddition, a validated method using calibration curves developed with a deuteratedinternal standard was used for the quantification of the psychoactive moleculeyangonin in various products.

RESULTS

DART-HRMS detected the protonated masses of six major kavalactonesand three flavokavains in 18 commercial Kava products. A method consistent withFDA validation guidelines was established for the quantification of yangonin in thevarious complex matrices. Implementation of this method, with an LLOQ of 5 mg/mL, enabled successful quantification of yangonin in 16 Kava products.Concentrations for solid products ranged from 2.71 to 8.99 mg/g, while that forliquid products ranged from 1.03 to 4.59 mg/mL.

CONCLUSIONS

Rapid identification and quantification of psychoactive smallmolecules in plant material can be accomplished using a validated DART-HRMSprotocol. This work illustrates an approach to qualitative and quantitative analysesof a wide variety of complex matrices derived from plants, and demonstrates thatthe commercially available products analyzed are P. methysticum derived and docontain psychoactive yangonin at quantifiable levels.

Cyclization of flavokawain B reduces its activity against human colon cancer cells

Chalcones are naturally occurring compounds exhibiting biological activity through multiple mechanisms. Flavokawain B is one of chalcones found in kava plant. In our studies, we focused on the anticancer activity of flavokawain B in colorectal cancer cells LoVo and its resistant to doxorubicin subline-LoVo/Dx. Strong cytotoxic activity of flavokawain B and its ability to inhibit the proliferation in both cell lines was detected. These effects accompanied with induction cell cycle arrest in G2/M phase and the presence of SubG1 fraction. Flavokawain B at low concentration led to increase of caspase-3 activity. The chalcone-induced apoptosis was also confirmed by DNA fragmentation. In our work, the conversion of flavokawain B to corresponding flavanone-5,7-dimetoxyflavanone-was shown to be more extensive in cancer than in non-cancer cells. We found that the cyclization of the chalcone was related to the significant decrease in the cytotoxicity. Cell proliferation and cell cycle progression were not impaired significantly in the studied cancer cells incubated with 5,7-dimethoxyflavanone. We did not observe apoptosis in the cells incubated with flavanone. The results from biological studies agreed with the theoretical activity that emerges from structural parameters.

The biosynthetic origin of psychoactive kavalactones in kava

Kava (Piper methysticum) is an ethnomedicinal shrub native to the Polynesian islands with well-established anxiolytic and analgesic properties. Its main psychoactive principles, kavalactones, form a unique class of polyketides that interact with the human central nervous system through mechanisms distinct from those of conventional psychiatric drugs. However, an unknown biosynthetic machinery and difficulty in chemical synthesis hinder the therapeutic use of kavalactones. In addition, kava also produces flavokavains, which are chalconoids with anticancer properties structurally related to kavalactones. Here, we report de novo elucidation of the key enzymes of the kavalactone and flavokavain biosynthetic network. We present the structural basis for the evolutionary development of a pair of paralogous styrylpyrone synthases that establish the kavalactone scaffold and the catalytic mechanism of a regio- and stereo-specific kavalactone reductase that produces a subset of chiral kavalactones. We further demonstrate the feasibility of engineering styrylpyrone production in heterologous hosts, thus opening a way to develop kavalactone-based non-addictive psychiatric therapeutics through synthetic biology.

Kavalactones and Flavokavins Profiles Contribute to Quality Assessment of Kava (Piper methysticum G. Forst.), the Traditional Beverage of the Pacific

Kava (Piper methysticum) is increasingly traded internationally and there is need for a rapid method to analyze kava raw material before export. The objectives of the present study were: (i) to develop a simple and robust protocol for high throughput simultaneous quantification of kavalactones (KLs) and flavokavins (FKs) in kava and (ii) to assess its potential for quality control. Methysticin; dihydromethysticin; kavain; desmethoxyyangonin; dihydrokavain; yangonin; and flavokavin A, B and C were quantified using HPTLC in acetonic extracts of 174 kava varieties. UHPLC analysis was conducted on a subset of six varieties representing the genetic variation of the species. The genetically distinct groups of nobles, two-day and wichmannii varieties were clearly differentiated and multivariate analyses of UHPLC and HPTLC data were congruent. Noble varieties have significantly low FKs/KLs (0.13) and high kavain/flavokavin B (K/FKB = 7.31). Two-day and wichmannii varieties are characterized by high FKs/KLs (0.36, 0.21) and low K/FKB (1.5, 1.7). A high-throughput HPTLC protocol was developed with a total analytical time of 50 min for 20 samples and only 10 mL of mobile phase. The use of acetone, sonication and two different detection wavelengths improves the accuracy compared to previous HPLC studies and confirms that kava varieties exhibit distinct chemotypes clearly differentiated by their FKs/KLs profiles. These results will strengthen the use of Codex Alimentarius regional standards.

A UHPLC-UV Method Development and Validation for Determining Kavalactones and Flavokavains in Piper methysticum (Kava)

An ultra-high-performance liquid chromatographic (UHPLC) separation was developed for six kava pyrones (methysticin, dihydromethysticin (DHM), kavain, dihydrokavain (DHK), desmethoxyyangonin (DMY), and yangonin), two unidentified components, and three Flavokavains (Flavokavain A, B, and C) in Piper methysticum (kava). The six major kavalactones and three flavokavains are completely separated (Rs > 1.5) within 15 min using a HSS T3 column and a mobile phase at 60 °C. All the peaks in the LC chromatogram of kava extract or standard solutions were structurally confirmed by LC-UV-MS/MS. The degradations of yangonin and flavokavains were observed among the method development. The degradation products were identified as cis-isomerization by MS/MS spectra. The isomerization was prevented or limited by sample preparation in a non-alcoholic solvent or with no water. The method uses the six kava pyrones and three flavokavains as external standards. The quantitative calibration curves are linear, covering a range of 0.5⁻75 μg/mL for the six kava pyrones and 0.05⁻7.5 μg/mL for the three flavokavains. The quantitation limits for methysticin, DHM, kavain, DHK, DMY, and yangonin are approximately 0.454, 0.480, 0.277, 0.686, 0.189, and 0.422 μg/mL. The limit of quantification (LOQs) of the three flavokavains are about 0.270, 0.062, and 0.303 μg/mL for flavokavain C (FKC), flavokavain A (FKA), and flavokavain B (FKB). The average recoveries at three different levels are 99.0⁻102.3% for kavalactones (KLs) and 98.1⁻102.9% for flavokavains (FKs). This study demonstrates that the method of analysis offers convenience and adequate sensitivity for determining methysticin, DHM, kavain, DHK, yangonin, DMY, FKA, FKB, and FKC in kava raw materials (root and CO₂ extract) and finished products (dry-filled capsule and tablet).

Anticancer activities of chalcone flavokawain B from Alpinia pricei Hayata in human lung adenocarcinoma (A549) cells via induction of reactive oxygen species-mediated apoptotic and autophagic cell death

Chalcones found in fruits and vegetables have promising cancer chemopreventive properties. This study attempts to identify the anticancer efficacies of chalcone flavokawain B (FKB) in the rhizomes of Alpinia pricei Hayata by examining key molecular events in non-small-cell lung cancer (A549) cells. Our results indicated that in human A549 cells, FKB (0-15 μg/ml) decreases cell viability and colony formation, dysregulates the Bax:B-cell lymphoma 2 ratio and increases apoptotic DNA fragmentation. Mitochondrial (caspase-9/-3 and poly ADP ribose polymerase [PARP]) signaling was found to be involved in FKB-induced apoptosis. In addition, FKB-induced reactive oxygen species (ROS) generation, and N-acetylcysteine attenuated FKB-induced apoptotic cell death. Moreover, FKB triggered autophagy, as evidenced by the improved acidic vesicular organelle formation, lipidated light chain 3 (microtubule-related light chain 3) accumulation, and ATG7 expression and the decreased mammalian target of rapamycin phosphorylation. Furthermore, FKB suppressed ROS-mediated ATG4B expression. Inhibiting autophagy using 3-methyladenine/chloroquine diminished FKB-induced cell death, indicating that autophagy is triggered as a death mechanism by FKB. In summary, FKB has a crucial role in the execution and propagation of ROS-mediated apoptotic and autophagic cell death of lung adenocarcinoma cells.

The Development of a Database for Herbal and Dietary Supplement Induced Liver Toxicity

The growing use of herbal dietary supplements (HDS) in the United States provides compelling evidence for risk of herbal-induced liver injury (HILI). Information on HDS products was retrieved from MedlinePlus of the U.S. National Library of Medicine and the herbal monograph of the European Medicines Agency. The hepatotoxic potential of HDS was ascertained by considering published case reports. Other relevant data were collected from governmental documents, public databases, web sources, and the literature. We collected information for 296 unique HDS products. Evidence of hepatotoxicity was reported for 67, that is 1 in 5, of these HDS products. The database revealed an apparent gender preponderance with women representing 61% of HILI cases. Culprit hepatotoxic HDS were mostly used for weight control, followed by pain and inflammation, mental stress, and mood disorders. Commonly discussed mechanistic events associated with HILI are reactive metabolites and oxidative stress, mitochondrial injury, as well as inhibition of transporters. HDS⁻drug interactions, causing both synergistic and antagonizing effects of drugs, were also reported for certain HDS. The database contains information for nearly 300 commonly used HDS products to provide a single-entry point for better comprehension of their impact on public health.

Isolation and Purification of Potent Growth Inhibitors from Piper methysticum Root

Piper methysticum (kava) root is known to possess promising weed suppressing activity. The present study was conducted to search for potent plant growth inhibitors from the root of this medicinal pepper plant. The ethyl acetate (EtOAc) extract exhibited the strongest reduction on growth of Raphanus sativus (radish) (IC₅₀ shoot and root growth = 172.00 and 51.31 µg/mL respectively) among solvent extracts. From this active extract, nine potent growth inhibitors involved in the inhibitory activities of P. methysticum root were isolated, purified and characterized by column chromatography (CC), gas chromatography-mass spectrometry (GC-MS), electrospray ionization-mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR). The six fractions purified by CC included two flavanones: 5-hydroxy-4′,7-dimethoxyflavanone (C1) and 5,7-dihydroxy-4′-methoxy-6,8-dimethylflavanone (matteucinol, C2) and six kavalactones: 5,6-dehydro-kavain (C3), a mixture of kavain and yagonin (C4), yagonin (C5) and dihydro-5,6-dehydrokavain, 7,8-dihydrokavain, dihydromethysticin and methysticin (C6). The amounts of 5-hydroxy-4′,7-dimethoxyflavanone, matteucinol, 5,6-dehydrokavain and yangonin were 0.76, 2.50, 2.75 and 2.09 mg/g dry weight (DW), respectively. The two flavanones C1 and C2 exhibited the strongest inhibition on shoot elongation (IC₅₀ = 120.22 and 248.03 µg/mL, respectively), whilst the two kavalactone mixtures C4 and C6 showed the highest suppression on root growth of R. sativus (IC₅₀ = 7.70 and 15.67 µg/mL, respectively). This study was the first to report the purification and inhibitory activities of the two flavanones 5-hydroxy-4′,7-dimethoxyflavanone and matteucinol in P. methysticum root. The isolated constituents from P. methysticum root including the flavanones C1 and C2 and the mixtures C4 and C6 may possess distinct modes of action on plant growth. Findings of this study highlighted that the combinations of hexane-ethyl acetate by 9:1 and 8:2 ratios successfully purified flavanones and kavalactones in P. methysticum root.

Toxicity Potential of Nutraceuticals

By the turn of the twenty-first century, the use of nutraceuticals became increasingly popular in both humans and animals due to their easy access, cost-effectiveness, and tolerability with a wide margin of safety. While some nutraceuticals are safe, others have a toxic potential. For a large number of nutraceuticals, no toxicity/safety data are available due to a lack of pharmacological/toxicological studies. The safety of some nutraceuticals can be compromised via contamination with toxic plants, metals, mycotoxins, pesticides, fertilizers, drugs of abuse, etc. Knowledge of pharmacokinetic/toxicokinetic studies appears to play a pivotal role in safety and toxicity assessment of nutraceuticals. Interaction studies are essential to determine efficacy, safety, and toxicity when nutraceuticals and therapeutic drugs are used concomitantly. This chapter describes various aspects of nutraceuticals, particularly their toxic potential, and the factors influencing their safety.

The In Vitro and In Vivo Antiangiogenic Effects of Flavokawain B

Angiogenesis is implicated in the development of a variety of pathological processes, most commonly cancer. It is essential for tumor growth and metastasis, making it an important cancer therapeutic target. Naturally occurring substances have led to the discovery of anticancer agents. Flavokawain B (FKB), a chalcone isolated from the root extracts of kava-kava plant, inhibits proliferation and causes apoptosis in vitro and in vivo of various cancer cell lines. The antimetastatic potential of FKB has also been suggested. In our study, we confirm the antiangiogenic action of FKB in vitro and, for the first time, demonstrate its strong antiangiogenic activity in vivo, using a zebrafish model. Our data show that FKB inhibits human brain endothelial cell (HUVEC) migration and tube formation even at very low and non-toxic concentrations. Moreover, FKB blocks angiogenesis process in zebrafish, with a dramatic reduction of subintestinal vein formation in a dose-dependent manner. Flavokawain B at the concentration of 2.5 μg/mL did not exhibit any toxic effects in zebrafish larvae and caused a markedly or complete obliteration of subintestinal vein formation. Our findings along with previously published data confirm that FKB may form the basis for creating an additional tool in the treatment of cancer and other neovascularization-related diseases. Copyright © 2017 John Wiley & Sons, Ltd.

Crude Extracts, Flavokawain B and Alpinetin Compounds from the Rhizome of Alpinia mutica Induce Cell Death via UCK2 Enzyme Inhibition and in Turn Reduce 18S rRNA Biosynthesis in HT-29 Cells

Uridine-cytidine kinase 2 is an enzyme that is overexpressed in abnormal cell growth and its implication is considered a hallmark of cancer. Due to the selective expression of UCK2 in cancer cells, a selective inhibition of this key enzyme necessitates the discovery of its potential inhibitors for cancer chemotherapy. The present study was carried out to demonstrate the potentials of natural phytochemicals from the rhizome of Alpinia mutica to inhibit UCK2 useful for colorectal cancer. Here, we employed the used of in vitro to investigate the effectiveness of natural UCK2 inhibitors to cause HT-29 cell death. Extracts, flavokawain B, and alpinetin compound from the rhizome of Alpinia mutica was used in the study. The study demonstrated that the expression of UCK2 mRNA were substantially reduced in treated HT-29 cells. In addition, downregulation in expression of 18S ribosomal RNA was also observed in all treated HT-29 cells. This was confirmed by fluorescence imaging to measure the level of expression of 18S ribosomal RNA in live cell images. The study suggests the possibility of MDM2 protein was downregulated and its suppression subsequently activates the expression of p53 during inhibition of UCK2 enzyme. The expression of p53 is directly linked to a blockage of cell cycle progression at G0/G1 phase and upregulates Bax, cytochrome c, and caspase 3 while Bcl2 was deregulated. In this respect, apoptosis induction and DNA fragmentation were observed in treated HT-29 cells. Initial results from in vitro studies have shown the ability of the bioactive compounds of flavokawain B and alpinetin to target UCK2 enzyme specifically, inducing cell cycle arrest and subsequently leading to cancer cell death, possibly through interfering the MDM2-p53 signalling pathway. These phenomena have proven that the bioactive compounds could be useful for future therapeutic use in colon cancer.

Gene Expression Analysis Reveals the Concurrent Activation of Proapoptotic and Antioxidant-Defensive Mechanisms in Flavokawain B-Treated Cervical Cancer HeLa Cells

Flavokawain B (FKB) is known to possess promising anticancer abilities. This is demonstrated in various cancer cell lines including HeLa cells. Cervical cancer is among the most widely diagnosed cancer among women today. Though FKB has been shown to be effective in treating cancer cells, the exact molecular mechanism is still unknown. This study is aimed at understanding the effects of FKB on HeLa cells using a microarray-based mRNA expression profiling and proteome profiling of stress-related proteins. The results of this study suggest that FKB induced cell death through p21-mediated cell cycle arrest and activation of p38. However, concurrent activation of antioxidant-related pathways and iron sequestration pathway followed by activation of ER-resident stress proteins clearly indicate that FKB failed to induce apoptosis in HeLa cells via oxidative stress. This effect implies that the protection of HeLa cells by FKB from H₂O₂–induced cell death is via neutralization of reactive oxygen species.

Hepatotoxicity Induced by "the 3Ks": Kava, Kratom and Khat

The 3Ks (kava, kratom and khat) are herbals that can potentially induce liver injuries. On the one hand, growing controversial data have been reported about the hepatotoxicity of kratom, while, on the other hand, even though kava and khat hepatotoxicity has been investigated, the hepatotoxic effects are still not clear. Chronic recreational use of kratom has been associated with rare instances of acute liver injury. Several studies and case reports have suggested that khat is hepatotoxic, leading to deranged liver enzymes and also histopathological evidence of acute hepatocellular degeneration. Numerous reports of severe hepatotoxicity potentially induced by kava have also been highlighted, both in the USA and Europe. The aim of this review is to focus on the different patterns and the mechanisms of hepatotoxicity induced by “the 3Ks”, while trying to clarify the numerous aspects that still need to be addressed.

In Silico Discovery of Potential Uridine-Cytidine Kinase 2 Inhibitors from the Rhizome of Alpinia mutica

Uridine-cytidine kinase 2 is implicated in uncontrolled proliferation of abnormal cells and it is a hallmark of cancer, therefore, there is need for effective inhibitors of this key enzyme. In this study, we employed the used of in silico studies to find effective UCK2 inhibitors of natural origin using bioinformatics tools. An in vitro kinase assay was established by measuring the amount of ADP production in the presence of ATP and 5-fluorouridine as a substrate. Molecular docking studies revealed an interesting ligand interaction with the UCK2 protein for both flavokawain B and alpinetin. Both compounds were found to reduce ADP production, possibly by inhibiting UCK2 activity in vitro. In conclusion, we have identified flavokawain B and alpinetin as potential natural UCK2 inhibitors as determined by their interactions with UCK2 protein using in silico molecular docking studies. This can provide information to identify lead candidates for further drug design and development.

Kavain Involvement in LPS-Induced Signaling Pathways

Kavain, a compound extracted from the Kava plant, Piper methysticum, is found to be involved in TNF-α expression in human and mouse cells via regulation of transcriptional factors such as NF-kB and LITAF. LITAF is known to activate the transcription of more than 20 cytokines that are involved in a variety of cellular processes and is associated with many inflammatory diseases, including angiogenesis, cancer, arthritis, and more. The modulation of LITAF is expected to positively affect cytokine-mediated diseases. Thus, intensive efforts have been deployed in search of LITAF inhibitors. In this work, we found that, in vitro, Kavain reduced LPS- induced TNF-α secretion in mouse macrophages, mouse bone marrow macrophages (BMM), and human peripheral blood mononuclear cells (HPBMC). We also found that Kavain treatment in RAW264.7 cells deactivated MyD88 and Akt, inhibited LITAF, and reduced the production of TNF-α, IL-27, and MIG in response to LPS. Similarly, it had a significant in vivo anti-inflammatory effect on wild-type (WT) mice that developed Collagen Antibody Induced Arthritis (CAIA). Overall, MyD88 was found to be an important mediator of the LPS-induced inflammatory response that can be distinguished from the NF-κB pathway. We also found that MyD88 is involved in the pathway linking LPS/LITAF to TNF-α. Therefore, given that Kavain modulates LPS-induced signaling pathways leading to cytokine expression, therapeutic interventions involving Kavain in inflammatory diseases are warranted. J. Cell. Biochem. 117: 2272-2280, 2016. © 2016 Wiley Periodicals, Inc.

Dihydro-5,6-dehydrokavain (DDK) from Alpinia zerumbet: Its Isolation, Synthesis, and Characterization

Dihydro-5,6-dehydrokavain (DDK) is the major and most promising component of the tropical plant Alpinia zerumbet (shell ginger), a species of the ginger family Zingiberaceae. Alpinia zerumbet is known for its human use as a traditional herbal medicine, food, and dietary supplement. With its α-lactone ring, DDK belongs to the large chemical group of kavalactones, which are also found in kava (Piper methysticum), another herbal medicine; DDK is characterized by a double-bond linkage at positions 5,6 and the absence of a double-bond linkage at positions 7,8. This dissociates DDK from other kavalactones with their linkages at positions 7,8 and 5,6 that are both either completely saturated or unsaturated, or may have an unsaturated bond at the position 7,8 as well as a saturated bond at the position 5,6. DDK is easily identified and quantified by HPLC and GC. DDK contents in fresh leaves, stems and rhizomes range from 80 to 410 mg/g, requiring solvent extraction procedures to ensure high DDK yield. This is best achieved by hexane extraction from fresh rhizomes that were previously boiled in water, allowing DDK yields of up to 424 mg/g. Successful synthesis of DDK can be achieved by asymmetric pathways, whereas its simple chemical structure facilitates the synthesis of DDK derivatives by HCl hydrolysis. Thus, all synthesized products may be used for various commercial purposes, including the potential development of promising antiobesity pharmaceutical drugs, preparation of specific and safe dietary supplements, and use as effective natural herbicides or fungicides.

Molecular targeted approaches to cancer therapy and prevention using chalcones

There is an emerging paradigm shift in oncology that seeks to emphasize molecularly targeted approaches for cancer prevention and therapy. Chalcones (1,3-diphenyl-2-propen-1-ones), naturally-occurring compounds with widespread distribution in spices, tea, beer, fruits and vegetables, consist of open-chain flavonoids in which the two aromatic rings are joined by a three-carbon α, β-unsaturated carbonyl system. Due to their structural diversity, relative ease of chemical manipulation and reaction of α, β-unsaturated carbonyl moiety with cysteine residues in proteins, some lead chalcones from both natural products and synthesis have been identified in a variety of screening assays for modulating important pathways or molecular targets in cancers. These pathways and targets that are affected by chalcones include MDM2/p53, tubulin, proteasome, NF-kappa B, TRIAL/death receptors and mitochondria mediated apoptotic pathways, cell cycle, STAT3, AP-1, NRF2, AR, ER, PPAR-γ and β-catenin/Wnt. Compared to current cancer targeted therapeutic drugs, chalcones have the advantages of being inexpensive, easily available and less toxic; the ease of synthesis of chalcones from substituted benzaldehydes and acetophenones also makes them an attractive drug scaffold. Therefore, this review is focused on molecular targets of chalcones and their potential implications in cancer prevention and therapy.

Contemporary Pacific and Western perspectives on `awa (Piper methysticum) toxicology

In 2010, a National Science Foundation project in Hawai`i assembled a collaboration of Pacific indigenous scientists, Hawaiian cultural practitioners and scientists trained in Western pharmacology. The objective of the collaborative project was to study Kava, a culturally significant Pacific beverage, and to address and ultimately transcend, long-standing barriers to communication and collaboration between these groups. Kava is a product of the `awa plant (Piper methysticum) that has been used ceremonially and medicinally throughout the history of Pacific Island cultures, and is now in widespread recreational and nutraceutical use in the US. This project, culminating in 2015, has enriched the participants, led to published work that integrates cultural and Western pharmacologic perspectives and established a paradigm for collaboration. This review paper integrates cultural and Western perspectives on efficacy, toxicity and the future cultural and commercial significance of `awa in the Pacific. Here we present a detailed review of traditional and non-traditional kava usage, medicinal efficacy and potential toxicological concerns. Recent mechanistic data on physiological action and potential pathological reactions are evaluated and interpreted.

Measuring the chemical and cytotoxic variability of commercially available kava (Piper methysticum G. Forster)

Formerly used world-wide as a popular botanical medicine to reduce anxiety, reports of hepatotoxicity linked to consuming kava extracts in the late 1990s have resulted in global restrictions on kava use and have hindered kava-related research. Despite its presence on the United States Food and Drug Administration consumer advisory list for the past decade, export data from kava producing countries implies that US kava imports, which are not publicly reported, are both increasing and of a fairly high volume. We have measured the variability in extract chemical composition and cytotoxicity towards human lung adenocarcinoma A549 cancer cells of 25 commercially available kava products. Results reveal a high level of variation in chemical content and cytotoxicity of currently available kava products. As public interest and use of kava products continues to increase in the United States, efforts to characterize products and expedite research of this potentially useful botanical medicine are necessary.

Flavokawains a and B in kava, not dihydromethysticin, potentiate acetaminophen-induced hepatotoxicity in C57BL/6 mice

Anxiolytic kava products have been associated with rare but severe hepatotoxicity in humans. This adverse potential has never been captured in animal models, and the responsible compound(s) remains to be determined. The lack of such knowledge greatly hinders the preparation of a safer kava product and limits its beneficial applications. In this study we evaluated the toxicity of kava as a single entity or in combination with acetaminophen (APAP) in C57BL/6 mice. Kava alone revealed no adverse effects for long-term usage even at a dose of 500 mg/kg bodyweight. On the contrary a three-day kava pretreatment potentiated APAP-induced hepatotoxicity, resulted in an increase in serum ALT and AST, and increased severity of liver lesions. Chalcone-based flavokawains A (FKA) and B (FKB) in kava recapitulated its hepatotoxic synergism with APAP while dihydromethysticin (DHM, a representative kavalactone and a potential lung cancer chemopreventive agent) had no such effect. These results, for the first time, demonstrate the hepatotoxic risk of kava and its chalcone-based FKA and FKB in vivo and suggest that herb–drug interaction may account for the rare hepatotoxicity associated with anxiolytic kava usage in humans.

Kava blocks 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung tumorigenesis in association with reducing O6-methylguanine DNA adduct in A/J mice

We previously reported the chemopreventive potential of kava against 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)- and benzo(a)pyrene (BaP)-induced lung tumorigenesis in A/J mice during the initiation and postinitiation stages. In this study, we investigated the tumorigenesis-stage specificity of kava, the potential active compounds, and the underlying mechanisms in NNK-induced lung tumorigenesis in A/J mice. In the first experiment, NNK-treated mice were given diets containing kava at a dose of 5 mg/g of diet during different periods. Kava treatments covering the initiation stage reduced the multiplicity of lung adenomas by approximately 99%. A minimum effective dose is yet to be defined because kava at two lower dosages (2.5 and 1.25 mg/g of diet) were equally effective as 5 mg/g of diet in completely inhibiting lung adenoma formation. Daily gavage of kava (one before, during, and after NNK treatment) completely blocked lung adenoma formation as well. Kavalactone-enriched fraction B fully recapitulated kava's chemopreventive efficacy, whereas kavalactone-free fractions A and C were much less effective. Mechanistically, kava and fraction B reduced NNK-induced DNA damage in lung tissues with a unique and preferential reduction in O(6)-methylguanine (O(6)-mG), the highly tumorigenic DNA damage by NNK, correlating and predictive of efficacy on blocking lung adenoma formation. Taken together, these results demonstrate the outstanding efficacy of kava in preventing NNK-induced lung tumorigenesis in A/J mice with high selectivity for the initiation stage in association with the reduction of O(6)-mG adduct in DNA. They also establish the knowledge basis for the identification of the active compound(s) in kava.

Antioxidant catalase rescues against high fat diet-induced cardiac dysfunction via an IKKβ-AMPK-dependent regulation of autophagy

Autophagy, a conservative degradation process for long-lived and damaged proteins, participates in a variety of biological processes including obesity. However, the precise mechanism of action behind obesity-induced changes in autophagy still remains elusive. This study was designed to examine the role of the antioxidant catalase in high fat diet-induced changes in cardiac geometry and function as well as the underlying mechanism of action involved with a focus on autophagy. Wild-type (WT) and transgenic mice with cardiac overexpression of catalase were fed low or high fat diet for 20 weeks prior to assessment of myocardial geometry and function. High fat diet intake triggered obesity, hyperinsulinemia, and hypertriglyceridemia, the effects of which were unaffected by catalase transgene. Myocardial geometry and function were compromised with fat diet intake as manifested by cardiac hypertrophy, enlarged left ventricular end systolic and diastolic diameters, fractional shortening, cardiomyocyte contractile capacity and intracellular Ca²⁺ mishandling, the effects of which were ameliorated by catalase. High fat diet intake promoted reactive oxygen species production and suppressed autophagy in the heart, the effects of which were attenuated by catalase. High fat diet intake dampened phosphorylation of inhibitor kappa B kinase β(IKKβ), AMP-activated protein kinase (AMPK) and tuberous sclerosis 2 (TSC2) while promoting phosphorylation of mTOR, the effects of which were ablated by catalase. In vitro study revealed that palmitic acid compromised cardiomyocyte autophagy and contractile function in a manner reminiscent of fat diet intake, the effect of which was significantly alleviated by inhibition of IKKβ, activation of AMPK and induction of autophagy. Taken together, our data revealed that the antioxidant catalase counteracts against high fat diet-induced cardiac geometric and functional anomalies possibly via an IKKβ-AMPK-dependent restoration of myocardial autophagy. This article is part of a Special Issue entitled: Autophagy and protein quality control in cardiometabolic diseases.

Insulin and IGFs enhance hepatocyte differentiation from human embryonic stem cells via the PI3K/AKT pathway

Human embryonic stem cells (hESCs) can be progressively differentiated into definitive endoderm (DE), hepatic progenitors, and hepatocytes, and thus provide an excellent model system for the mechanistic study of hepatocyte differentiation, which is currently poorly understood. Here, we found that insulin enhanced hepatocyte differentiation from hESC-derived DE. Insulin activated the PI3K/AKT pathway, but not the mitogen-activated protein kinase pathway in the DE cells, and inhibition of the PI3K/AKT pathways by inhibitors markedly inhibited hepatocyte differentiation. In addition, insulin-like growth factor 1 (IGF1) and IGF2 also activated the PI3K/AKT pathway in DE cells and their expression was robustly upregulated during hepatocyte differentiation from DE. Furthermore, inhibition of IGF receptor 1 (IGF1R) by a small molecule inhibitor PPP or knockdown of the IGF1R by shRNA attenuated hepatocyte differentiation. Moreover, simultaneous knockdown of the IGF1R and the insulin receptor with shRNAs markedly reduced the activation of AKT and substantially impaired hepatocyte differentiation. The PI3K pathway specifically enhanced the expression of HNF1 and HNF4 to regulate hepatocyte differentiation from DE. Although inhibition of the PI3K pathway was previously shown to be required for the induction of DE from hESCs, our study revealed a positive role of the PI3K pathway in hepatocyte differentiation after the DE stage, and has advanced our understanding of hepatocyte cell fate determination.

The chalcones cardamonin and flavokawain B inhibit the differentiation of preadipocytes to adipocytes by activating ERK

AIM

We searched for polyphenols capable of inhibiting the lipid accumulation in 3T3-L1 cells, and investigated the mechanisms of two effective chalcones cardamonin and flavokawain B on differentiation of preadipocytes.

METHOD AND RESULTS

We treated 3T3-L1 cells with a panel of 46 polyphenols and measured intracellular lipid accumulation by Sudan II staining. Four of them, including cardamonin and flavokawain B, inhibited lipid accumulation. In the further study, cardamonin and flavokawain B inhibited lipid accumulation by downregulating the expression of CCAAT/enhancer binding protein (C/EBP)-β, C/EBPα, and peroxisome proliferator-activated receptor-γ (PPARγ) at both mRNA and protein levels. Cardamonin and flavokawain B also increased phosphorylation of extracellular signal-regulated kinase (ERK) in the early phase of adipocyte differentiation. PD98059, an ERK inhibitor, restored C/EBPβ, PPARγ expression and intracellular lipid accumulation in adipocytes. Moreover, cardamonin and flavokawain B also modulated the secretion of C-reactive protein, dipeptidyl peptidase IV, interleukin-6, tumor necrosis factor-α and fibroblast growth factor-21 in mature adipocytes.

CONCLUSIONS

These results indicate that ERK activation and consequent downregulation of adipocyte-specific transcription factors are involved in the inhibitory effects of the chalcones cardamonin and flavokawain B on adipocyte differentiation. Moreover, cardamonin and flavokawain B are able to modulate secretion of adipokines in mature adipocytes.

Dietary feeding of Flavokawain A, a Kava chalcone, exhibits a satisfactory safety profile and its association with enhancement of phase II enzymes in mice

Flavokawain A (FKA), a major chalcone in the Kava plant, has recently demonstrated promising anti-cancer activities. A systematic evaluation of FKA's safety profile has not been reported before. In this study, male FVB/N mice were fed with an AIN-76A diet or AIN-76A diet supplemented with 0.6% (6 g/kg food) FKA or 0.6% commercial kava root extract (KRE) for three weeks. Dietary feeding of FKA did not affect food consumption and body weight. Histopathological examination of liver, kidney, colon, lung, heart, spleen, and thymus revealed no signs of FKA-induced toxicity. Biochemical serum analysis and histological examination confirmed normal organ function in FKA-treated mice. The cytotoxicity profile showed FKA had minimal side effects on bone marrow and small intestinal epithelial cells compared with Adriamycin. In addition, oral feeding of FKA increased activities of both glutathione S-transferase and quinone reductase in the liver, lung, prostate and bladder tissues of mice. In comparison, dietary feeding of 0.6% KRE increased liver/body weight ratio and decreased spleen, thymus, and testis/body weight ratios, as well as induced nodular proliferation in liver tissues. Therefore, dietary feeding FKA showed no adverse effects on major organ function and homeostasis in mice, suggesting the potential of FKA for chemoprevention study of human cancers.

Detection of flavokavins (A, B, C) in cultivars of kava (Piper methysticum) using high performance thin layer chromatography (HPTLC)

Kava (Piper methysticum) is used to prepare the traditional beverage of the Pacific islands. In Europe, kava has been suspected to cause hepatoxicity with flavokavin B (FKB) considered as a possible factor. The present study describes an HPTLC protocol for rapid screening of samples. The objectives are: to detect the presence of flavokavins in extracts and to compare the FKB levels in different cultivars. Overall, 172 samples originating from four cultivars groups (noble, medicinal, two-days and wichmannii), were analysed. Results indicate that the ratio FKB/kavalactones is much higher in two-days (0.39) and wichmannii (0.32) compared to nobles (0.09) and medicinal cultivars (0.10). For each group, the ratios flavokavins/kavalactones do not change significantly between roots, stumps or basal stems and among clones, indicating that they are genetically controlled. This protocol has good accuracy and is cost efficient for routine analysis. We discuss how it could be used for quality control.