Antidiabetogenic oligostilbenoids and 3-ethyl-4-phenyl-3,4-dihydroisocoumarins from the bark of Shorea roxburghii

Phytochemical and pharmacological profile of genus shorea: A review of the recent literature

In tropical Southeast Asia, Shorea is the most economically important tree and the largest genus in the Dipterocarpaceae family. It comprises about 150-200 species, of which majority are distributed in Malaysia, with others found in Sumatra and Borneo (Kalimantan) in Indonesia. Research on the chemical constituents of Shorea plants has been ongoing for many years. To date, a total of 113 different compounds, including 83 stilbenes and their resveratrol oligomers, 18 triterpenes/terpenoids, 7 coumarins 3 flavonoids and 2 steroids have been isolated and successfully elucidated from 26 different species of this genus. The diversity of the stilbene resveratrol oligomers in the Shorea genus is primarily due to the difference in the amount of resveratrol constituent units, which include dimers, trimers and tetramers. In addition to the species' traditional usage in the treatment of illnesses, such as diarrhea, toothaches, skin diseases, ear troubles and wounds, the extracts and secondary metabolite compounds isolated from various parts of the plant species are known to have a very potent antioxidant, antimicrobial, anticancer, anti-diabetic, anti-obesity, antiulcer, hepatoprotective and nephroprotective activities. This review aims to summarize the most recent research made from 1999 to date on the secondary metabolite compounds isolated from different species of genus Shorea, as well as the bioactivity (in vitro and in vivo) of the crude extracts and the isolated secondary metabolite compounds.

The Natural Stilbenoid (-)-Hopeaphenol Inhibits HIV Transcription by Targeting Both PKC and NF-κB Signaling and Cyclin-Dependent Kinase 9

Despite effective combination antiretroviral therapy (cART), people living with HIV (PLWH) continue to harbor replication-competent and transcriptionally active virus in infected cells, which in turn can lead to ongoing viral antigen production, chronic inflammation, and increased risk of age-related comorbidities. To identify new agents that may inhibit postintegration HIV beyond cART, we screened a library of 512 pure compounds derived from natural products and identified (-)-hopeaphenol as an inhibitor of HIV postintegration transcription at low to submicromolar concentrations without cytotoxicity. Using a combination of global RNA sequencing, plasmid-based reporter assays, and enzyme activity studies, we document that hopeaphenol inhibits protein kinase C (PKC)- and downstream NF-κB-dependent HIV transcription as well as a subset of PKC-dependent T-cell activation markers, including interleukin-2 (IL-2) cytokine and CD25 and HLA-DRB1 RNA production. In contrast, it does not substantially inhibit the early PKC-mediated T-cell activation marker CD69 production of IL-6 or NF-κB signaling induced by tumor necrosis factor alpha (TNF-α). We further show that hopeaphenol can inhibit cyclin-dependent kinase 9 (CDK9) enzymatic activity required for HIV transcription. Finally, it inhibits HIV replication in peripheral blood mononuclear cells (PBMCs) infected in vitro and dampens viral reactivation in CD4+ cells from PLWH. Our study identifies hopeaphenol as a novel inhibitor that targets a subset of PKC-mediated T-cell activation pathways in addition to CDK9 to block HIV expression. Hopeaphenol-based therapies could complement current antiretroviral therapy otherwise not targeting cell-associated HIV RNA and residual antigen production in PLWH.

Pharmaceutical Food Science: Search for Bio-Functional Molecules Obtained from Natural Resources to Prevent and Ameliorate Lifestyle Diseases

In this review, our resent pharmaceutical food science research for bio-functional molecules obtained from natural resources that contribute to i) suppression of postprandial blood glucose elevation and/or improvement of glucose tolerance and ii) reduction of visceral fat accumulation and improvement of lipid metabolism were summarized. Based on studies using MONOTORI science, salacinol (1), neokotalanol (4), and trans-tiliroside (20) have been approved or notified by the Consumer Affairs Agency in Japan as functional substances in food with health claims, Food for Specified Health Use and Food with Functional Claims.

Chemistry, Biosynthesis and Pharmacology of Viniferin: Potential Resveratrol-Derived Molecules for New Drug Discovery, Development and Therapy

Viniferin is a resveratrol derivative. Resveratrol is the most prominent stilbenoid synthesized by plants as a defense mechanism in response to microbial attack, toxins, infections or UV radiation. Different forms of viniferin exist, including alpha-viniferin (α-viniferin), beta-viniferin (β-viniferin), delta-viniferin (δ-viniferin), epsilon-viniferin (ε-viniferin), gamma-viniferin (γ-viniferin), R-viniferin (vitisin A), and R2-viniferin (vitisin B). All of these forms exhibit a range of important biological activities and, therefore, have several possible applications in clinical research and future drug development. In this review, we present a comprehensive literature search on the chemistry and biosynthesis of and the diverse studies conducted on viniferin, especially with regards to its anti-inflammatory, antipsoriasis, antidiabetic, antiplasmodic, anticancer, anti-angiogenic, antioxidant, anti-melanogenic, neurodegenerative effects, antiviral, antimicrobial, antifungal, antidiarrhea, anti-obesity and anthelminthic activities. In addition to highlighting its important chemical and biological activities, coherent and environmentally acceptable methods for establishing vinferin on a large scale are highlighted to allow the development of further research that can help to exploit its properties and develop new phyto-pharmaceuticals. Overall, viniferin and its derivatives have the potential to be the most effective nutritional supplement and supplementary medication, especially as a therapeutic approach. More researchers will be aware of viniferin as a pharmaceutical drug as a consequence of this review, and they will be encouraged to investigate viniferin and its derivatives as pharmaceutical drugs to prevent future health catastrophes caused by a variety of serious illnesses.

The Natural Stilbenoid (-)-Hopeaphenol Inhibits Cellular Entry of SARS-CoV-2 USA-WA1/2020, B.1.1.7, and B.1.351 Variants

Antivirals are urgently needed to combat the global SARS-CoV-2/COVID-19 pandemic, supplement existing vaccine efforts, and target emerging SARS-CoV-2 variants of concern. Small molecules that interfere with binding of the viral spike receptor binding domain (RBD) to the host angiotensin-converting enzyme II (ACE2) receptor may be effective inhibitors of SARS-CoV-2 cell entry. Here, we screened 512 pure compounds derived from natural products using a high-throughput RBD/ACE2 binding assay and identified (-)-hopeaphenol, a resveratrol tetramer, in addition to vatalbinoside A and vaticanol B, as potent and selective inhibitors of RBD/ACE2 binding and viral entry. For example, (-)-hopeaphenol disrupted RBD/ACE2 binding with a 50% inhibitory concentration (IC50) of 0.11 μM, in contrast to an IC50 of 28.3 μM against the unrelated host ligand/receptor binding pair PD-1/PD-L1 (selectivity index, 257.3). When assessed against the USA-WA1/2020 variant, (-)-hopeaphenol also inhibited entry of a VSVΔG-GFP reporter pseudovirus expressing SARS-CoV-2 spike into ACE2-expressing Vero-E6 cells and in vitro replication of infectious virus in cytopathic effect and yield reduction assays (50% effective concentrations [EC50s], 10.2 to 23.4 μM) without cytotoxicity and approaching the activities of the control antiviral remdesivir (EC50s, 1.0 to 7.3 μM). Notably, (-)-hopeaphenol also inhibited two emerging variants of concern, B.1.1.7/Alpha and B.1.351/Beta in both viral and spike-containing pseudovirus assays with similar or improved activities over the USA-WA1/2020 variant. These results identify (-)-hopeaphenol and related stilbenoid analogues as potent and selective inhibitors of viral entry across multiple SARS-CoV-2 variants of concern.

A review of antidiabetic active thiosugar sulfoniums, salacinol and neokotalanol, from plants of the genus Salacia

During our studies characterizing functional substances from food resources for the prevention and treatment of lifestyle-related diseases, we isolated the active constituents, salacinol (1) and neokotalanol (4), and related thiosugar sulfoniums, from the roots and stems of the genus Salacia plants [Celastraceae (Hippocrateaceae)] such as Salacia reticulata Wight, S. oblonga Wall., and S. chinensis L., and observed their antidiabetic effects. These plant materials have been used traditionally in Ayurvedic medicine as a specific remedy at the early stage of diabetes, and have been extensively consumed in Japan, the United States, and other countries as a food supplement for the prevention of obesity and diabetes. Here, we review our studies on the antidiabetic effects of plants from the genus Salacia, from basic chemical and pharmacological research to their application and development as new functional food ingredients.

Assessment of the anti-diabetic potential of the Cratoxylum formosum subsp. formosum extracts via carbohydrate hydrolyzing enzymes inhibitory activities

Introduction: This research aims to evaluate the anti-diabetic activity of the extracts from different parts of Cratoxylum formosum subsp. formosum.Methods: The in vitro inhibitory activities of the hexane (HEX), dichloromethane (DCM) and ethyl acetate (EtOAc) extracts from the flowers, leaves, roots and stems on pancreatic α-amylase (pAA), Saccharomyces α-glucosidase (SAG), rat intestinal maltase (rIM), and sucrase (rIS) were investigated. Results: The DCM and EtOAc extracts from the flowers (IC50 5.4 ± 1.5 and 10.5 ± 0.6 µg/mL) displayed the similar inhibitory activities as acarbose (IC50 7.2 ± 0.4 µg/mL) in the pAA assay. The inhibitory activities of the DCM and EtOAc extracts from the flowers (IC50 56.7 ± 8.9 and 20.4 ± 0.4 µg/mL), EtOAc extract from leaves (IC50 45.0 ± 3.5 µg/mL), DCM and EtOAc extracts from roots (IC50 35.0 ± 6.7 and 16.7± 3.6 µg/mL), and EtOAc extract from stems (IC50 31.1 ± 7.3 µg/mL) were more potent than acarbose (IC50 431.4 ± 16.7 µg/mL) on SAG inhibitory assay (P<0.05). In the rIM assay, DCM and EtOAc extracts from the flowers (IC50 8.5 ± 0.2 and 12.4 ± 0.3 µg/mL) exhibited stronger inhibitory activity than acarbose (IC50 38.5 ± 7.2 µg/mL) (P<0.05). Moreover, the inhibitory activity of DCM extract from the flowers (IC50 16.9 ± 1.5 µg/ mL) was comparable to the acarbose (IC50 15.5 ± 1.2 µg/mL) on rIS assay. Conclusion: The DCM and EtOAc extracts from the flowers were more active than the leaves, roots and stems in the inhibition of our defined target enzymes.

Shorea roxburghii Leaf Extract Ameliorates Hyperglycemia Induced Abnormalities in High Fat/Fructose and Streptozotocin Induced Diabetic Rats

This study investigated the hypoglycemic effect of the methanol extract of Shorea roxburghii leaves (SRL) in high fat diet/high fructose solution (HFDHF) and streptozotocin (STZ) induced type 2 diabetes mellitus (T2DM) in rats as well as evaluating its ameliorative potentials in altered biochemical and hematological parameters in the treated rats. T2DM was induced in Sprague Dawley (SD) rats by feeding with HFDHF for 4 weeks and administering STZ (35 mg/kg, i. p.). Diabetic rats were given SRL extract at doses of 100 and 400 mg/kg for 30 days. The food and water intake were monitored on a daily basis, while the fasting blood glucose (FBG) levels and body weight were measured weekly. Biochemical and hematological parameters as well as histopathological studies of the pancreas were also evaluated. SRL significantly decreased FBG and improved the body weight, food and water intake of treated diabetic rats. Furthermore, biochemical and hematological parameters including liver and kidney function enzymes, lipid profiles, white blood and red blood cells parameters were markedly ameliorated by SRL. Histopathological analyses of the pancreas indicated reconstitution of β-cells architecture in SRL treated rats. The results of this study suggest that SRL has antidiabetic potential and can be considered for the treatment of T2DM.

Shoreanol A and B, unprecedented oligostilbenoids from the twigs of Shorea obtusa Wall

Chemical investigation of the twigs extract of tropical dipterocarpaceous plant Shorea obtusa Wall led to the isolation of two previously undescribed oligostilbenoids, including a structurally unusual resveratrol aneuploid named shoreanol A (1) and a new resveratrol trimer derivative named shoreanol B (2). Their structures and relative configurations were determined by comprehensive spectroscopic analysis and comparison with previously reported compound. Shoreanol A (1) was identified as a rare natural resveratrol aneuploid possessing a novel carbon skeleton through condensation of three resveratrol monomer and one benzyl moiety, which is the first example in the Dipterocarpaceae. While shoreanol B (2) was characterized to be the first example of stilbene trimer bearing an epoxy group in the genus Shorea.

Ampelopsin E Reduces the Invasiveness of the Triple Negative Breast Cancer Cell Line, MDA-MB-231

Breast cancer is the most common and the second leading cause of cancer-related deaths in women. It has two distinctive hallmarks: rapid abnormal growth and the ability to invade and metastasize. During metastasis, cancer cells are thought to form actin-rich protrusions, called invadopodia, which degrade the extracellular matrix. Current breast cancer treatments, particularly chemotherapy, comes with adverse effects like immunosuppression, resistance development and secondary tumour formation. Hence, naturally-occurring molecules claimed to be less toxic are being studied as new drug candidates. Ampelopsin E, a natural oligostilbene extracted from Dryobalanops species, has exhibited various pharmacological properties, including anticancer and anti-inflammatory activities. However, there is yet no scientific evidence of the effects of ampelopsin E towards metastasis. Scratch assay, transwell migration and invasion assays, invadopodia and gelatin degradation assays, and ELISA were used to determine the effects of ampelopsin E towards the invasiveness of MDA-MB-231 cells. Strikingly in this study, ampelopsin E was able to halt migration, transmigration and invasion in MDA-MB-231 cells by reducing formation of invadopodia and its degradation capability through significant reduction (p < 0.05) in expression levels of PDGF, MMP2, MMP9 and MMP14. In conclusion, ampelopsin E reduced the invasiveness of MDA-MB-231 cells and was proven to be a potential alternative in treating TNBC.

A Review of Biologically Active Natural Products from a Desert Plant Cistanche tubulosa

An Orobanchaceae plant Cistanche tubulosa (SCHENK) WIGHT (Kanka-nikujuyou in Japanese), which is one of the authorized plant resources as Cistanches Herba in both Japanese and Chinese Pharmacopoeias, is a perennial parasitic plant growing on roots of sand-fixing plants. The stems of C. tubulosa have traditionally been used for treatment of impotence, sterility, lumbago, and body weakness as well as a promoting agent of blood circulation. In recent years, Cistanches Herba has also been widely used as a health food supplement in Japan, China, and Southeast Asian countries. Here we review our recent studies on chemical constituents from the stems of C. tubulosa as well as their bioactivities such as vasorelaxtant, hepatoprotective, and glucose tolerance improving effects.

Isolation and characterization of resveratrol oligomers from the stem bark of Hopea ponga (Dennst.) Mabb. And their antidiabetic effect by modulation of digestive enzymes, protein glycation and glucose uptake in L6 myocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Hopea ponga (Dennst.) Mabb. Is used in traditional herbal formulations for diabetes complications. The aim of this study is to evaluate the antidiabetic effect of extracts and compounds from H. ponga.

MATERIALS AND METHODS

Silica gel column chromatography was performed to identify various chemical components of the plant extract. Different extracts of H. ponga and isolated compounds were screened for their antidiabetic effect by modulation of digestive enzymes and protein glycation. The effect of glucose uptake by the compounds and the pathways through which the compounds mediate the glucose uptake potential were confirmed by fluorescent microscopy, flow cytometry and western blot analysis.

RESULTS

Acetone and ethanol extracts of the stem bark of Hopea ponga (Dennst.) Mabb. Afforded six resveratrol oligomers namely, E-resveratrol (1), (-)-ε-viniferin (2), (-)-α-viniferin (3), trihydroxyphenanthrene glucoside (THPG) (4), vaticaphenol A (5), (-)-hopeaphenol (6), along with four phytosterols. The structures were determined on the basis of spectroscopic analyses including nuclear magnetic resonance (NMR) spectroscopy and high resolution mass spectrometry (HRMS) data. Compounds 1-5 and 7-10 were tested for their α-glucosidase, α-amylase and glycation inhibitiory activities. All the resveratrol oligomers (1-5) showed prominent α-glucosidase inhibition with IC₅₀ values, 12.56 ± 1.00, 23.98 ± 1.11, 7.17 ± 1.10, 31.74 ± 0.42 and 16.95 ± 0.39 μM, respectively. Molecular docking studies also supported the observed α-glucosidase inhibition. Compound 3 displayed IC₅₀ values of 4.85 ± 0.06 and 27.10 ± 0.04 μM in α-amylase and glycation inhibitory assays activity. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay revealed that the compounds 3 and 4 were found to be less toxic at a concentration of 100 μM (<10%) and 25 μM (<20%), respectively. The effect of glucose uptake performed by 2-(N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG) in L6 myoblast were measured by fluorescent microscopy and flow cytometry. The compounds 3 and 4 showed 2-NBDG uptake of 49.6% and 38.8% respectively. By examining the molecular pathway through which the compounds elicit their glucose uptake potential, it was observed that both the compounds mainly act via AMPK pathway.

CONCLUSION

This is the first report on the isolation of compounds from H. ponga. Altogether, the results of this study reveal the antidiabetic effects of H. ponga extracts and isolated compounds promoting traditional use of this plant in the treatment of diabetes.

One-pot, three-component approach to diarylacetonitriles

Described herein is a novel one-pot, three-component reaction where aldehydes, electron-rich arenes, and TMSCN in the presence of BF₃-OEt₂ allowed direct access to a number of diarylacetonitriles under mild reaction conditions in good to excellent yields.

Cataract Preventive Role of Isolated Phytoconstituents: Findings from a Decade of Research

Cataract is an eye disease with clouding of the eye lens leading to disrupted vision, which often develops slowly and causes blurriness of the eyesight. Although the restoration of the vision in people with cataract is conducted through surgery, the costs and risks remain an issue. Botanical drugs have been evaluated for their potential efficacies in reducing cataract formation decades ago and major active phytoconstituents were isolated from the plant extracts. The aim of this review is to find effective phytoconstituents in cataract treatments in vitro, ex vivo, and in vivo. A literature search was synthesized from the databases of Pubmed, Science Direct, Google Scholar, Web of Science, and Scopus using different combinations of keywords. Selection of all manuscripts were based on inclusion and exclusion criteria together with analysis of publication year, plant species, isolated phytoconstituents, and evaluated cataract activities. Scientists have focused their attention not only for anti-cataract activity in vitro, but also in ex vivo and in vivo from the review of active phytoconstituents in medicinal plants. In our present review, we identified 58 active phytoconstituents with strong anti-cataract effects at in vitro and ex vivo with lack of in vivo studies. Considering the benefits of anti-cataract activities require critical evaluation, more in vivo and clinical trials need to be conducted to increase our understanding on the possible mechanisms of action and the therapeutic effects.

Update on Phytochemistry and Pharmacology of Naturally Occurring Resveratrol Oligomers

Resveratrol oligomers (REVs), a major class of stilbenoids, are biosynthesized by regioselective oxidative coupling of two to eight units of resveratrol monomer. Due to their unique structures and pleiotropic biological activities, natural product chemists are increasingly focusing on REVs in the last few decades. This study presents a detailed and thorough examination of REVs, including chemical structures, natural resources, and biological activities, during the period of 2010–2017. Ninety-two new REVs compounds, including 39 dimers, 23 trimers, 13 tetramers, six resveratrol monomers, six hexamers, four pentamers, and one octamer, have been reported from the families of Dipterocarpaceae, Paeoniaceae, Vitaceae, Leguminosae, Gnetaceae, Cyperaceae, Polygonaceae Gramineae, and Poaceae. Amongst these families, Dipterocarpaceae, with 50 REVs, accounts for the majority, and seven genera of Dipterocarpaceae are involved, including Vatica, Vateria, Shorea, Hopea, Neobalanocarpus, Dipterocarpus, and Dryobalanops. These REVs have shown a wide range of bioactivities. Pharmacological studies have mainly focused on potential efficacy on tumors, bacteria, Alzheimer’s disease, cardiovascular diseases, and others. The information updated in this review might assist further research and development of novel REVs as potential therapeutic agents.

Anti-Inflammatory Effects of Vitisinol A and Four Other Oligostilbenes from Ampelopsis brevipedunculata var. Hancei

In this study, the cytotoxicities and anti-inflammatory activities of five resveratrol derivatives-vitisinol A, (+)-ε-viniferin, (+)-vitisin A, (-)-vitisin B, and (+)-hopeaphenol-isolated from Ampelopsis brevipedunculata var. hancei were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and lipopolysaccharide (LPS)-stimulated RAW264.7 cells, respectively. The result from MTT assay analysis indicated that vitisinol A has lower cytotoxicity than the other four well-known oligostilbenes. In the presence of vitisinol A (5 μM), the significant reduction of inflammation product (nitric oxide, NO) in LPS-induced RAW264.7 cells was measured using Griess reaction assay. In addition, the under-expressed inflammation factors cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) in LPS-induced RAW264.7 cells monitored by Western blotting simultaneously suggested that vitisinol A has higher anti-inflammatory effect compared with other resveratrol derivatives. Finally, the anti-inflammatory effect of vitisinol A was further demonstrated on 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced ear edema in mice. As a preliminary functional evaluation of natural product, the anti-inflammatory effect of vitisinol A is the first to be examined and reported by this study.

Quantitative Determination of Stilbenoids and Dihydroisocoumarins in Shorea roxburghii and Evaluation of Their Hepatoprotective Activity

A simultaneous quantitative analytical method for 13 stilbenoids including (-)-hopeaphenol (1), (+)-isohopeaphenol (2), hemsleyanol D (3), (-)-ampelopsin H (4), vaticanols A (5), E (6), and G (7), (+)-α-viniferin (8), pauciflorol A (9), hopeafuran (10), (-)-balanocarpol (11), (-)-ampelopsin A (12), and trans-resveratrol 10-C-β-d-glucopyranoside (13), and two dihydroisocoumarins, phayomphenols A₁ (14) and A₂ (15) in the extract of Shorea roxburghii (dipterocarpaceae) was developed. According to the established protocol, distributions of these 15 polyphenols (1-15) in the bark and wood parts of S. roxburghii and a related plant Cotylelobium melanoxylon were evaluated. In addition, the principal polyphenols (1, 2, 8, 13-15) exhibited hepatoprotective effects against d-galactosamine (d-galN)/lipopolysaccharide (LPS)-induced liver injury in mice at a dose of 100 or 200 mg/kg, p.o. To characterize the mechanisms of action, the isolates were examined in in vitro studies assessing their effects on (i) d-GalN-induced cytotoxicity in primary cultured mouse hepatocytes; (ii) LPS-induced nitric oxide (NO) production in mouse peritoneal macrophages; and (iii) tumor necrosis factor-α (TNF-α)-induced cytotoxicity in L929 cells. The mechanisms of action of these polyphenols (1, 2, and 8) were suggested to be dependent on the inhibition of LPS-induced macrophage activation and reduction of sensitivity of hepatocytes to TNF-α. However, none of the isolates reduced the cytotoxicity caused by d-GalN.

Inhibitory Effects of Oligostilbenoids from the Bark of Shorea roxburghii on Malignant Melanoma Cell Growth: Implications for Novel Topical Anticancer Candidates

Human malignant melanomas remain associated with dismal prognosis due to their resistance to apoptosis and chemotherapy. There is growing interest in plant oligostilbenoids owing to their pleiotropic biological activities, including anti-inflammatory, antioxidant, and anticancer effects. Recent studies have demonstrated that resveratrol, a well-known stilbenoid from red wine, exhibits cell cycle-disrupting and apoptosis-inducing activities on melanoma cells. The objective of our study was to evaluate the anti-melanoma effect of oligostilbenoids isolated from the bark of Shorea roxburghii. Among the isolates, four resveratrol oligomers, i.e., (-)-hopeaphenol, vaticanol B, hemsleyanol D, and (+)-α-viniferin, possessed more potent antiproliferative action than did resveratrol against SK-MEL-28 melanoma cells. Cell cycle analysis revealed that (-)-hopeaphenol, hemsleyanol D, and (+)-α-viniferin arrested cell division cycle at the G1 phase, whereas vaticanol B had little effect on the cell cycle. In addition, cell proliferation assay also revealed that (+)-α-viniferin induced DNA damage followed by induction of apoptosis in SK-MEL-28 cells, which was confirmed by an increased expression of γ-H2AX and cleaved caspase-3, respectively. The compounds vaticanol B, hemsleyanol D, and resveratrol significantly increased the expression of p21, suggesting that they are able to block cell cycle progression. Moreover, these oligostilbenoids downmodulated cylin D1 expression and extracellular signal-regulated kinase (ERK) activation. Furthermore, hemsleyanol D, (+)-α-viniferin, and resveratrol significantly decreased the expression of cyclin B1, which could also suppress cell cycle progression. The present study thus suggests that these plant oligostilbenoids are effective as therapeutic or chemopreventive agents against melanoma.

Targeting glucose metabolism for healthy aging

Advancing age is the greatest single risk factor for numerous chronic diseases. Thus, the ability to target the aging process can facilitate improved healthspan and potentially lifespan. Lack of adequate glucoregulatory control remains a recurrent theme accompanying aging and chronic disease, while numerous longevity interventions result in maintenance of glucoregulatory control. In this review, we propose targeting glucose metabolism to enhance regulatory control as a means to ameliorate the aging process. We highlight that calorie restriction improves glucoregulatory control and extends both lifespan and healthspan in model organisms, but we also indicate more practical interventions (i.e., calorie restriction mimetics) are desirable for clinical application in humans. Of the calorie restriction mimetics being investigated, we focus on the type 2 diabetes drug acarbose, an α-glucosidase inhibitor that when taken with a meal, results in reduced enzymatic degradation and absorption of glucose from complex carbohydrates. We discuss alternatives to acarbose that yield similar physiologic effects and describe dietary sources (e.g., sweet potatoes, legumes, and berries) of bioactive compounds with α-glucosidase inhibitory activity. We indicate future research should include exploration of how non-caloric compounds like α-glucosidase inhibitors modify macronutrient metabolism prior to disease onset, which may guide nutritional/lifestyle interventions to support health and reduce age-related disease risk.

Induction of apoptosis and G2/M arrest by ampelopsin E from Dryobalanops towards triple negative breast cancer cells, MDA-MB-231

BACKGROUND

Several compounds isolated from Dryobalanops have been reported to exhibit cytotoxic effects to several cancer cell lines. This study investigated the cytotoxic effects, cell cycle arrest and mode of cell death in ampelopsin E-treated triple negative cells, MDA-MB-231.

METHODS

Cytotoxicity of ampelopsin E, ampelopsin F, flexuosol A, laevifonol, Malaysianol A, Malaysianol D and nepalensinol E isolated from Dryobalanops towards human colon cancer HT-29, breast cancer MDA-MB-231 and MCF-7, alveolar carcinoma HeLa and mouse embryonic fibroblast NIH/3 T3 cells were determined by MTT assay. The cells were treated with the compounds (0.94-30 μM) for 72 h. The mode of cell death was evaluated by using an inverted light microscope and annexin V/PI analysis. Cell cycle analysis was performed by using a flow cytometer.

RESULTS

Data showed that ampelopsin E was most cytotoxic toward MDA-MB-231 with the IC50 (50 % inhibition of cell viability compared to control) of 14.5 ± 0.71 μM at 72 h. Cell shrinkage, membrane blebbing and formation apoptotic bodies characteristic of apoptosis were observed following treatment with ampelopsin E. The annexin V/PI flow cytometric analysis further confirmed that ampelopsin E induced apoptosis in MDA-MB-231 cells. Cell cycle analysis revealed that ampelopsin E induced G2/M phase cell cycle arrest in the cells.

CONCLUSION

Ampelopsin E induced apoptosis and cell cycle arrest in MDA-MB-231 cells. Therefore, ampelopsin E has the potential to be developed into an anticancer agent for treatment of triple negative breast cancer.

Polyphenol compounds and PKC signaling

BACKGROUND

Naturally occurring polyphenols found in food sources provide huge health benefits. Several polyphenolic compounds are implicated in the prevention of disease states, such as cancer. One of the mechanisms by which polyphenols exert their biological actions is by interfering in the protein kinase C (PKC) signaling pathways. PKC belongs to a superfamily of serine-threonine kinase and are primarily involved in phosphorylation of target proteins controlling activation and inhibition of many cellular processes directly or indirectly.

SCOPE OF REVIEW

Despite the availability of substantial literature data on polyphenols' regulation of PKC, no comprehensive review article is currently available on this subject. This article reviews PKC-polyphenol interactions and its relevance to various disease states. In particular, salient features of polyphenols, PKC, interactions of naturally occurring polyphenols with PKC, and future perspective of research on this subject are discussed.

MAJOR CONCLUSIONS

Some polyphenols exert their antioxidant properties by regulating the transcription of the antioxidant enzyme genes through PKC signaling. Regulation of PKC by polyphenols is isoform dependent. The activation or inhibition of PKC by polyphenols has been found to be dependent on the presence of membrane, Ca(2+) ion, cofactors, cell and tissue types etc. Two polyphenols, curcumin and resveratrol are in clinical trials for the treatment of colon cancer.

GENERAL SIGNIFICANCE

The fact that 74% of the cancer drugs are derived from natural sources, naturally occurring polyphenols or its simple analogs with improved bioavailability may have the potential to be cancer drugs in the future.

N-Heterocyclic carbene-triggered transition-metal-free synthesis of 2,3-disubstituted benzofuran derivatives

An NHC-triggered, transition-metal-free strategy for the efficient synthesis of 2,3-disubstituted benzofuran derivatives in moderate to excellent yields from aryl or alkyl aldehydes and o-quinone methides has been developed.

Dipeptidyl peptidase-IV inhibitory activity of dimeric dihydrochalcone glycosides from flowers of Helichrysum arenarium

A methanol extract of everlasting flowers of Helichrysum arenarium L. Moench (Asteraceae) was found to inhibit the increase in blood glucose elevation in sucrose-loaded mice at 500 mg/kg p.o. The methanol extract also inhibited the enzymatic activity against dipeptidyl peptidase-IV (DPP-IV, IC50 = 41.2 μg/ml), but did not show intestinal α-glucosidase inhibitory activities. From the extract, three new dimeric dihydrochalcone glycosides, arenariumosides V-VII (2-4), were isolated, and the stereostructures were elucidated based on their spectroscopic properties and chemical evidence. Of the constituents, several flavonoid constituents, including 2-4, were isolated, and these isolated constituents were investigated for their DPP-IV inhibitory effects. Among them, chalconaringenin 2'-O-β-D-glucopyranoside (16, IC50 = 23.1 μM) and aureusidin 6-O-β-D-glucopyranoside (35, 24.3 μM) showed relatively strong inhibitory activities.

Acylated phenylethanoid glycosides, echinacoside and acteoside from Cistanche tubulosa, improve glucose tolerance in mice

Acylated phenylethanoid glycosides, echinacoside (1) and acteoside (2), principal constituents in stems of Cistanche tubulosa (Orobanchaceae), inhibited the increase in postprandial blood glucose levels in starch-loaded mice at doses of 250-500 mg/kg p.o. These compounds (1 and 2) also significantly improved glucose tolerance in starch-loaded mice after 2 weeks of continuous administration at doses of 125 and/or 250 mg/kg/day p.o. without producing significant changes in body weight or food intake. In addition, several constituents from C. tubulosa, including 1 (IC50 = 3.1 μM), 2 (1.2 μM), isoacteoside (3, 4.6 μM), 2'-acetylacteoside (4, 0.071 μM), tubulosides A (5, 8.8 μM) and B (9, 4.0 μM), syringalide A 3-O-α-L-rhamnopyranoside (10, 1.1 μM), campneoside I (13, 0.53 μM), and kankanoside J1 (14, 9.3 μM), demonstrated potent rat lens aldose reductase inhibitory activity. In particular, the potency of compound 4 was similar to that of epalrestat (0.072 μM), a clinical aldose reductase inhibitor.

Antioxidant activity of the stem bark of Shorea roxburghii and its silver reducing power

A detailed study has been performed on the antioxidant activity of the acetone and methanol extracts of the stem bark of the plant, Shorea roxburghii. The total phenolic content and antioxidant activity of the extracts were determined by DPPH, radical scavenging, ferric ion reducing power, hydroxyl radical, ABTS^. radical scavenging and hydrogen peroxide scavenging activities. Reducing efficiency of the S. roxburghii towards silver nanoparticles has been evaluated using surface plasmon resonance and transmission electron microscope. Spherical shapes of particles with 4–50 nm have been reported. Formation of silver nanoparticles ascertains the role of the water soluble phenolic compounds present in S. roxburghii. Both acetone and methanol extracts of S. roxburghii stem bark was found to be a potent antioxidant. This work provides a scientific support for the high antioxidant activity of this plant and thus it may find potential applications in the treatment of the diseases caused by free radical. The extract of this plant could be used as a green reducing agent for the synthesis of Ag nanoparticles.