Inhibition of ATPase activity of Escherichia coli ATP synthase by polyphenols

We have studied the inhibitory effect of five polyphenols namely, resveratrol, piceatannol, quercetin, quercetrin, and quercetin-3-β-d glucoside on Escherichia coli ATP synthase. Recently published X-ray crystal structures of bovine mitochondrial ATP synthase inhibited by resveratrol, piceatannol, and quercetin, suggest that these compounds bind in a hydrophobic pocket between the γ-subunit C-terminal tip and the hydrophobic inside of the surrounding annulus in a region critical for rotation of the γ-subunit. Herein, we show that resveratrol, piceatannol, quercetin, quercetrin, or quercetin-3-β-d glucoside all inhibit E. coli ATP synthase but to different degrees. Whereas piceatannol inhibited ATPase essentially completely (～0 residual activity), inhibition by other compounds was partial with ～20% residual activity by quercetin, ～50% residual activity by quercetin-3-β-d glucoside, and ～60% residual activity by quercetrin or resveratrol. Piceatannol was the most potent inhibitor (IC₅₀ ～14 μM) followed by quercetin (IC₅₀ ～33 μM), quercetin-3-β-d glucoside (IC₅₀ ～71 μM), resveratrol (IC₅₀ ～94 μM), quercitrin (IC₅₀ ～120 μM). Inhibition was identical in both F₁F_o membrane preparations as well as in isolated purified F₁. In all cases inhibition was reversible. Interestingly, resveratrol and piceatannol inhibited both ATPase and ATP synthesis whereas quercetin, quercetrin or quercetin-3-β-d glucoside inhibited only ATPase activity and not ATP synthesis.     

Substrate specificity in vivo and in vitro in the formation of stilbenes. Biosynthesis of rhaponticin

The biosynthesis of the stilbene glucoside rhaponticin (3,5,3′-trihydroxy-4′-methoxystilbene 3-O-β-d-glucoside), a constituent of rhubarb (Rheum rhaponticum), was localized in the rhizome. Acetate and various phenylpropane derivatives were tested as precursors in feeding experiments. p-Coumaric acid was more efficiently incorporated than isoferulic acid, resveratrol (3,5,4′-trihydroxystilbene) was found to be the best precursor of rhaponticin. In vitro, for the stilbene-synthesizing system an even higher selectivity in favor of the p-hydroxy compound was observed. When various cinnamoyl-CoA derivatives were tested, membrane-bound enzyme preparations from rhizome converted at pH 7.5p-coumaroyl-CoA into resveratrol whereas rhapontigenin was not formed from isoferuloyl-CoA. Caffeoyl-CoA was converted to astringenin, but with lower rates and at a more acidic pH. The stilbene skeleton is, therefore, synthesized from a phenylpropane moiety carrying a 4′-hydroxysubstitution, while further derivatization to the 3′-hydroxy-4′-methoxy structure takes place at the level of stilbenes.     

Biotransformation of piceid in Polygonum cuspidatum to resveratrol by Aspergillus oryzae

Biotransformation of piceid in Polygonum cuspidatum to resveratrol by Aspergillus oryzae was investigated in this study. Resveratrol is widely used in medicine, food, and cosmetic because of its pharmacological properties. However, it has a much lower content in plants compared with its glucoside piceid, which has a much lower bioavailability. Traditionally, the aglycone is acquired by acid or enzymatic hydrolysis of its glucoside, but the violent condition and the acid pollution in hydrolytic reaction and the high cost of the enzyme limit their industrial development. In this paper, fermentation of P. cuspidatum by A. oryzae was successfully performed, during which, piceid was converted to resveratrol with the highest yield of trans-resveratrol 1.35%, 3.6 times higher than that obtained from raw herb by microwave-assisted extraction. Scale-up production was also performed and the yield of trans-resveratrol was 3.1 times higher after 24 h incubation. Therefore, biotransformation is a better method to increase the yield of resveratrol because of its high yield and mild conditions.     

Structure of renifolin and reconfirmation of the structure of pirolatin

The ¹H and ¹³C NMR spectral analysis of the glucoside renifolin, isolated from Pyrola renifolia, demonstrated the so far unknown binding site of the glucose moiety to be at C-8 and hence its structure as 8-β-D-glucosyloxy-2,7-dimethyl-1,4-dihydronaphthalen-5-ol. The earlier reported structure for the glucoside pirolatin, isolated from Pyrola japonica, was also reconfirmed by the ¹³C NMR spectral analysis.     

Resveratrol as a Pan-HDAC Inhibitor Alters the Acetylation Status of Jistone Proteins in Human-Derived Hepatoblastoma Cells

The polyphenolic alcohol resveratrol has demonstrated promising activities for the prevention and treatment of cancer. Different modes of action have been described for resveratrol including the activation of sirtuins, which represent the class III histone deacetylases (HDACs). However, little is known about the activity of resveratrol on the classical HDACs of class I, II and IV, although these classes are involved in cancer development or progression and inhibitors of HDACs (HDACi) are currently under investigation as promising novel anticancer drugs. We could show by in silico docking studies that resveratrol has the chemical structure to inhibit the activity of different human HDAC enzymes. In vitro analyses of overall HDAC inhibition and a detailed HDAC profiling showed that resveratrol inhibited all eleven human HDACs of class I, II and IV in a dose-dependent manner. Transferring this molecular mechanism into cancer therapy strategies, resveratrol treatment was analyzed on solid tumor cell lines. Despite the fact that hepatocellular carcinoma (HCC) is known to be particularly resistant against conventional chemotherapeutics, treatment of HCC with established HDACi already has shown promising results. Testing of resveratrol on hepatoma cell lines HepG2, Hep3B and HuH7 revealed a dose-dependent antiproliferative effect on all cell lines. Interestingly, only for HepG2 cells a specific inhibition of HDACs and in turn a histone hyperacetylation caused by resveratrol was detected. Additional testing of human blood samples demonstrated a HDACi activity by resveratrol ex vivo. Concluding toxicity studies showed that primary human hepatocytes tolerated resveratrol, whereas in vivo chicken embryotoxicity assays demonstrated severe toxicity at high concentrations. Taken together, this novel pan-HDACi activity opens up a new perspective of resveratrol for cancer therapy alone or in combination with other chemotherapeutics. Moreover, resveratrol may serve as a lead structure for chemical optimization of bioavailability, pharmacology or HDAC inhibition.     

Locustoside A — A new purine alkaloid glucoside from seeds of Gleditsia japonica

A new purine alkaloid glucoside designated locustoside A has been isolated from the seeds of Gleditsia japonica, which has been used in oriental traditional medicine. The structure was determined as 7-β-d-glucopyranosyl-3-(3-methyl-2-butenyl)-isoguanine by interpretation of spectroscopic data and was confirmed by X-ray crystallographic analysis.     

Grayanoside D,A diterpene glucoside from Leucothoe Grayana

A new diterpenoid glucoside, grayanoside D, has been isolated from Leucothoe grayana. Its structure was elucidated by chemical and spectroscopic means and by correlation with grayanotoxin-XV to be 3-O-(β-D-glucopyranosyl)-(10S)-dihydrograyanotoxin-XV.     

Grayanoside C,a new diterpene glucoside from Leucothoe grayana

A new diterpene glucoside has been isolated from Leucothoe grayana. Its structure was elucidated by X-ray diffraction analysis of a dehydrated product of the aglycone and conversion of the same to leucothol A.     

The 4′-Hydroxyl Group of Resveratrol Is Functionally Important for Direct Activation of PPARα

Long-term moderate consumption of red wine is associated with a reduced risk of developing lifestyle-related diseases such as cardiovascular disease and cancer. Therefore, resveratrol, a constituent of grapes and various other plants, has attracted substantial interest. This study focused on one molecular target of resveratrol, the peroxisome proliferator activated receptor α (PPARα). Our previous study in mice showed that resveratrol-mediated protection of the brain against stroke requires activation of PPARα; however, the molecular mechanisms involved in this process remain unknown. Here, we evaluated the chemical basis of the resveratrol-mediated activation of PPARα by performing a docking mode simulation and examining the structure-activity relationships of various polyphenols. The results of experiments using the crystal structure of the PPARα ligand-binding domain and an analysis of the activation of PPARα by a resveratrol analog 4-phenylazophenol (4-PAP) in vivo indicate that the 4′-hydroxyl group of resveratrol is critical for the direct activation of PPARα. Activation of PPARα by 5 μM resveratrol was enhanced by rolipram, an inhibitor of phosphodiesterase (PDE) and forskolin, an activator of adenylate cyclase. We also found that resveratrol has a higher PDE inhibitory activity (IC₅₀ = 19 μM) than resveratrol analogs trans-4-hydroxystilbene and 4-PAP (IC₅₀ = 27-28 μM), both of which has only 4′-hydroxyl group, indicating that this 4′-hydroxyl group of resveratrol is not sufficient for the inhibition of PDE. This result is consistent with that 10 μM resveratrol has a higher agonistic activity of PPARα than these analogs, suggesting that there is a feedforward activation loop of PPARα by resveratrol, which may be involved in the long-term effects of resveratrol in vivo.     

Effect of plant stilbene precursors on the biosynthesis of resveratrol in Vitis amurensis Rupr. Cell cultures

The biosynthesis of resveratrol after the application of a precursor for biosynthesis, i.e., phenylalanine (Phe), has been studied. The application of Phe has been shown to increase significantly the expression of the phenylalanine-ammonia-lyase (PAL) and stilbene synthase (STS) genes and enhance the production of resveratrol by 8.5 times. Data on resveratrol production after the addition of Phe and coumaric acid (CA) were compared with known analogs.     

Lobodirin: Ein neues chromonglucosid aus Lobodirina cerebriformis

From the lichen Lobodirina cerebriformis (Mont.) Follm. Roccellaceae) a new chromone glucoside lobodirin (I) has been isolated. The structure, 7-0-β-d-triacetylglucosyl-isoeugenitol, was established by hydrolysis to glucose isoeugenitol by synthesis of acetyllobodirin from α-acetobromoglucose and isoeugenitol with subsequent acetylation.     

Comparative studies of polydatin and resveratrol on mutual transformation and antioxidative effect in vivo

BackgroundPolydatin and resveratrol are extractives of radix or rhizoma of Polygonum cuspidatum, and as the glycoside forms, it is a natural precursor of resveratrol.PurposeIn this study, we aimed to explore the mutual transformation between polydatin and resveratrol in rats, and to compare the antioxidative effect of them in vivo.Study designIn this study, we analyzed the serum molar concentration of polydatin and resveratrol after oral administration in rats and evaluated the anti-oxidative stress effects of them using a mouse model.MethodsRats were orally administered polydatin or resveratrol and the concentration of them in serum were analyzed by high performance liquid chromatography (HPLC). Their antioxidative effect was compared in mice with oxidative stress cardiomyopathy induced by doxorubicin (DOX).ResultsThe results showed that polydatin and resveratrol could mutually transform in vivo, the molar concentration of polydatin in serum was always averagely 3.35 and 4.28 times as much as resveratrol after oral administration of polydatin and resveratrol at 200 mg/kg, respectively. Both polydatin and resveratrol could significantly decrease the content of malonydialdehyde (MDA), promote the activities of total superoxide dismutase (T-SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) in plasma, and increase the content of glutathione (GSH) in myocardial tissue. The effect of polydatin surpassed resveratrol, particularly embodied in increasing the activities of T-SOD and CAT, and the content of GSH.ConclusionIt illustrates that polydatin is the main substance in serum after intragastric administration with polydatin or resveratrol, and the mutual transformation between polydatin and resveratrol keeps balance; they both have the ability of antioxidative stress in vivo, and polydatin has a better effect than resveratrol, which hints that polydatin may be a substitute for resveratrol in antioxidant for clinical use.     

Identification of pterostilbene as a phytoalexin from Vitis vinifera leaves

An inducible antifungal compound in grapevine leaves (Vitis vinifera L., cv Cabernet-Sauvignon) has been identified as trans-pterostilbene (3,5-dimethoxy-4′-hydroxy stilbene). It is only a minor component of the phytoalexin response of V. vinifera but its antifungal activity is relatively high by comparison with resveratrol and the viniferins, stress metabolites which have been identified previously in grapevine. Methods for the quantitative analysis of pterostilbene, resveratrol, ε- and α-viniferins by HPLC are described.     

Production of a major stilbene phytoalexin, resveratrol in peanut (Arachis hypogaea) and peanut products: a mini review

As a major stilbene phytoalexin, resveratrol is produced or elicited in several plant species as a part of defense systems protecting plants against diseases. Resveratrol can be present in both the trans- and cis-isomeric forms, and only the trans-form increases the life expectancy and lowers the risk of cardiovascular diseases as the most bioactive form. In addition to the usages for diet and industry, peanut plant (Arachis hypogaea) and peanuts are getting higher attention due to their containment of resveratrol in the kernels and other parts of peanut plant, such as leaves, roots, and peanut shell. Recently, natural resveratrol derived from peanuts has also become a promising nutraceutical agent, promoting human health. Resveratrol has also been detected in peanut products including peanut butters, roasted peanuts, and boiled peanuts. Although, smaller and immature peanuts contain higher levels of resveratrol than mature peanuts, resveratrol in peanuts can also be preserved by cooking or manufacturing processes. Moreover, the amount of resveratrol in peanut plants and peanuts has been found to increase by external stimuli including microbial infection, wounding, UV light irradiation, ultrasonication, yeast extract treatment and by plant stress hormones. In addition, molecular level analysis has confirmed that four resveratrol synthase (RS) genes (RS1, RS2, RS3 and RS4) which catalyze synthesis of resveratrol have been identified in peanuts, and up-regulation of the genes is positively correlated to the increased contents of resveratrol. In this review, we summarize the natural biosynthesis of resveratrol in peanuts and peanut plants, as well as the occurrence of this natural phytoalexin in various peanut products. A brief knowledge on the biosynthetic pathway of resveratrol synthesis has been described. This review also deals on highlighting the effect of various external stimuli (biotic and abiotic stresses) in order to achieve the maximum induction and/or elicitation of resveratrol in peanuts and peanut plants.     

Resveratrol with antioxidant activity inhibits matrix metalloproteinase via modulation of SIRT1 in human fibrosarcoma cells

AimsResveratrol, a silent information regulator 1 (SIRT1) activator, has been reported to act as an antioxidant contained in red wine and prevent the development of cardiovascular diseases. Histone deacetylase such as SIRT1 is involved in the regulation of lifespan extension. In this study, the effect of resveratrol on matrix metalloproteinases (MMPs) that play an important role in metastasis was examined in human fibrosarcoma cell line, HT1080.Main methodsThe effect of resveratrol on MMPs' activity was evaluated using gelatin zymography. Western blot analysis and RT-PCR assay were used to determine the effect of resveratrol on the expression level of MMP-9, MAPK and SIRT1 proteins and genes, respectively.Key findingsIt was observed that resveratrol exhibited not only antioxidant effects on lipid peroxidation and DNA oxidation but also inhibitory effects on the expression of MMP-2 and 9 in HT1080 cells stimulated with either phorbol myristate acetate or phenazine methosulfate. Furthermore, it was found that treatment with resveratrol decreased the level of MMP-9 expression via down-regulation of p-ERK, c-fos and p65. In addition, the level of SIRT1 gene expression was also enhanced by treatment of resveratrol alone but the level of MMP-9 gene expression was decreased.SignificanceThese results suggest that the activation of SIRT1 in the presence of resveratrol especially inhibits the expression of MMP-9 in HT1080 cells, providing evidence that resveratrol can be a potential candidate for chemoprevention of cancer.     

Influence of calcium influx induced by the calcium ionophore, A23187, on resveratrol content and the expression of CDPK and STS genes in the cell cultures of Vitis amurensis

The present study examines the effect of calcium influx induced by the calcium ionophore (CI) on the biosynthesis of resveratrol and the expression of stilbene synthase (STS) and calcium-dependent protein kinase (CDPK) genes in cell cultures of Vitis amurensis, which have different levels of resveratrol production. The present study utilized the control cell culture V2 of V. amurensis, which contains no more than 0.02?% dry weight (DW) of resveratrol, in addition to rolB transgenic cell cultures VB1 and VB2, which have increased resveratrol contents (0.1–0.8?% DW). Treatment with the CI at a 1?μM concentration significantly increased STS gene expression (6 of 10 analyzed STS genes) and resveratrol production in the control V2 cell culture by fourfold; however, use of the CI at 10?μM significantly decreased resveratrol production by 2–4 fold in all cell cultures tested. In the control V2 grape cell culture, treatment with the CI increased expression of all of the CDPK genes except VaCDPK1a and VaCDPK3a. In the rolB transgenic VB2 grape cell culture treated with the CI, we detected alterations in expression of several CDPK genes, but these changes in gene expression were not significant. Our results indicated that treatment with 1?μM of the CI increased resveratrol content and production in control grape cells by selectively increasing the expression of STS genes. Conversely, the CI treatment did not significantly increase resveratrol content and production, or the expression of CDPK or STS genes in the rolB transgenic cells. Likely, untreated VB2 cells have increased concentrations of cytoplasmic calcium, and therefore, treatment with the CI did not significantly change CDPK expression. These results suggest that the rolB gene has an important role in the regulation of calcium-dependent transduction pathways in transformed cells.     

Structural elucidation and partial synthesis of 3-hydroxyheterodendrin,a cyanogenic glucoside from Acacia sieberiana var. woodii

A new cyanogenic glucoside, isolated from pods of Acacia sieberiana var. woodii, was shown to be (2R)-2- (β-d-glucopyranosyloxy)-3-hydroxy-3-methylbutanenitrile by spectroscopic and chemical methods. The absolute configuration of this glucoside was correlated with that of proacacipetalin by oxymercuration of the latter, followed by borohydride reduction of the product.     

New indanone compounds from Onychium japonicum

A new indanone glucoside pteroside M has been isolated from fronds of Onychium japonicumPteridaceae. The structure of its aglycone pterosin M has been established by ¹³C NMR, PMR spectra and degradation with nitric acid.