Inhibitory effects of flavonoids on rabbit heart carbonyl reductase

Cardiorenal dysfunction and hypertrophy induced by renal artery occlusion are normalized by galangin treatment in rats

Galangin is a polyphenolic compound found in Alpinia officinarum and propolis. This study investigated the effect of galangin on blood pressure, the renin angiotensin system (RAS), cardiac and kidney alterations and oxidative stress in two-kidney one-clipped (2K-1C) hypertensive rats. Hypertension was induced in male Sprague Dawley rats (180-220 g), and the rats were given galangin (30 and 60 mg/kg) and losartan (10 mg/kg) for 4 weeks (n = 8/group). Galangin decreased hypertension and cardiac dysfunction and hypertrophy, which was related to the reducing circulation angiotensin converting enzyme (ACE) activity and angiotensin II concentration (p < 0.05). These effects were consistent with the reduced overexpression of angiotensin II receptor type 1 (AT₁R), transforming growth factor beta 1 (TGF-β1) and collagen type I (Col I) protein in cardiac tissue (p < 0.05). Additionally, renal artery occlusion, procedure-induced kidney dysfunction and fibrosis were attenuated in the galangin-treated group. Galangin treatment normalized the overexpression of AT₁R and NADPH oxidase 4 (Nox-4) protein and normalized the downregulation of nuclear factor-erythroid Factor 2-related Factor 2 (Nrf-2) and haem oxygenase 1 (HO-1) in 2K-1C rats (p < 0.05). Galangin exhibited antioxidative effects, as it reduced systemic and tissue oxidative stress markers and increased catalase activity in 2K-1C rats (p < 0.05). In conclusion, galangin attenuated hypertension, renin-angiotensin system activation, cardiorenal damage and oxidative stress induced by renal artery stenosis in rats. These effects might be associated with modulation of the expression of AT₁R, TGF-β1 and Col I protein in the heart as well as AT₁R/Nox-4 and Nrf-2/HO-1 protein in renal tissue in hypertensive rats.

Comparison for quantification of eight components in Alpinia officinarum Hance by using high-performance liquid chromatography coupled with diode array detector and charged aerosol detector with individual and substitute reference compound

An efficient HPLC-DAD-CAD method was developed and compared for simultaneous quantification of four flavonoids and four diarylheptanoids in Alpinia officinarum Hance (A. officinarum) using individual and substitute reference compound. All calibration curves for investigated analytes showed good linear regression (R²> 0.9991). The LODs of investigated compounds for DAD and CAD were 0.15-7.92 ng (0.03-1.58 μg/mL) and 2.91-3.95 ng (0.58-0.79 μg/mL), respectively, whereas the LOQs were 0.52-26.39 ng (0.10-5.28 μg/mL) for DAD, and 9.70-13.18 ng (1.94-2.64 μg/mL) for CAD. Recoveries of all analytes, which ranged from 96.58% to 100.06% for DAD, and from 96.29% to 99.61% for CAD, were acceptable. According to the quantitative results, the eight compounds in A. officinarum can be accurately quantified with individual calibration curves by two detectors. In addition, to overcome the bottleneck of shortage of reference standards, diphenylheptane A and galangin, respectively, were selected for direct or calibrated quantitative determination of other diarylheptanoids and flavonoids in A. officinarum. The results showed the contents of eight components in A. officinarum determined by these methods were similar, which suggested that substitute reference compound was suitable for quantification of its analogues.

Galangin alleviates vascular dysfunction and remodelling through modulation of the TNF-R1, p-NF-κB and VCAM-1 pathways in hypertensive rats

Galangin is a natural flavonoid isolated from ginger, honey and propolis.

AIMS

To investigate the effect of galangin on blood pressure, vascular changes, sympathoexcitation, oxidative stress and inflammation in rats treated with N^G-nitro-l-arginine methyl ester (l-NAME).

MATERIALS AND METHODS

Male Wistar rats (220-250 g) were given l-NAME (0.5 mg/mL in drinking water) to induce hypertension for 5 weeks. They were treated with vehicle, galangin (30 or 60 mg/kg), or amlodipine (10 mg/kg) for the final two weeks (n = 6/group).

KEY FINDINGS

Galangin significantly reduced blood pressure and improved the impairment of endothelium-dependent vasodilation in hypertensive rats. Sympathoexcitation, including enhancement of contractile responses to electrical field stimulation, increases in intensity of tyrosine hydroxylase and plasma norepinephrine concentration in hypertensive rats, was attenuated by galangin treatment. Galangin also reduced systemic and vascular oxidative damage and increased plasma nitric oxide levels in the hypertensive groups. Aortic remodelling accompanied by aortic wall hypertrophy and fibrosis observed in hypertensive rats were alleviated by galangin treatment. Furthermore, galangin exhibited an anti-inflammatory effect by suppressing the upregulation of tumour necrosis factor receptor 1 (TNF-R1), phospho-nuclear factor kappa B (p-NF-κB) and vascular cell adhesion protein 1 (VCAM-1) in aortic tissue and reducing plasma tumour necrosis factor alpha (TNF-α) in l-NAME rats. In conclusion, galangin had antihypertensive effects that were relevant to attenuating endothelial dysfunction, sympathoexcitation and vascular remodelling. These effects might be contributed by antioxidant and anti-inflammatory capacities and modulation of the TNF-R1, p-NF-κB and VCAM-1 pathways in hypertensive rats.

Forest biorefinery: Potential of poplar phytochemicals as value-added co-products

The global forestry industry after experiencing a market downturn during the past decade has now aimed its vision towards the integrated biorefinery. New business models and strategies are constantly being explored to re-invent the global wood and pulp/paper industry through sustainable resource exploitation. The goal is to produce diversified, innovative and revenue generating product lines using on-site bioresources (wood and tree residues). The most popular product lines are generally produced from wood fibers (biofuels, pulp/paper, biomaterials, and bio/chemicals). However, the bark and other tree residues like foliage that constitute forest wastes, still remain largely an underexploited resource from which extractives and phytochemicals can be harnessed as by-products (biopharmaceuticals, food additives and nutraceuticals, biopesticides, cosmetics). Commercially, Populus (poplar) tree species including hybrid varieties are cultivated as a fast growing bioenergy crop, but can also be utilized to produce bio-based chemicals. This review identifies and underlines the potential of natural products (phytochemicals) from Populus species that could lead to new business ventures in biorefineries and contribute to the bioeconomy. In brief, this review highlights the importance of by-products/co-products in forest industries, methods that can be employed to extract and purify poplar phytochemicals, the potential pharmaceutical and other uses of >160 phytochemicals identified from poplar species - their chemical structures, properties and bioactivities, the challenges and limitations of utilizing poplar phytochemicals, and potential commercial opportunities. Finally, the overall discussion and conclusion are made considering the recent biotechnological advances in phytochemical research to indicate the areas for future commercial applications from poplar tree species.

Dihydroquercetin: More than just an impurity?

Dihydroquercetin (taxifolin) is a potent flavonoid found in onions, French maritime bark, milk thistle, tamarind seeds and commercially available semi-synthetic monoHER marketed as Venoruton. This review focuses on the therapeutic promise of dihydroquercetin in major disease states such as cancer, cardiovascular disease and liver disease by reviewing the proposed mechanism(s) of action, including the activation of the antioxidant response element (ARE) and detoxifying phase II enzymes, inhibition of cytochrome P(450) and fatty acid synthase in carcinogenesis. TNF-alpha and NF-ĸB dependent transcription in hepatitis C infections, the scavenging effect of myeloperoxidase (MPO) derived reactive nitrogen species and subsequent effects on cholesterol biosynthesis as well as the effects on apob/apoA-I, HMG-CoA reductase and apoptosis are reviewed. The stereochemistry and pro-oxidant effect of dihydroquercetin are also considered. Although the majority of research on dihydroquercetin to date has focused on the identification of molecular targets in vitro, this review will bring together evidence of the potency and mode of action of dihydroquercetin and will propose a role for the therapeutic potential of flavonoid antioxidants.

Effect of galangin supplementation on oxidative damage and inflammatory changes in fructose-fed rat liver

The study examined the effects of galangin (GA) on oxidative stress, inflammatory cytokine levels and nuclear factor-kappa B (NF-κB) activation in fructose-fed rat liver. Adult male albino Wistar rats were divided into 4 groups. Groups 1 and 4 received the control diet containing starch as the source of carbohydrate while groups 2 and 3 were fed a diet containing fructose. Groups 3 and 4 additionally received GA (100μg/kg, p.o) from the 15th day. At the end of 60 days, the levels of plasma glucose, insulin and triglycerides, insulin sensitivity indices and oxidative stress markers in the liver were determined. Cytokines of interest were assayed by ELISA and RT-PCR and NF-κB p65 nuclear translocation by Western blot and RT-PCR. Compared to control diet-fed animals, fructose-fed animals developed hyperglycemia, hyperinsulinemia, hypertriglyceridemia and insulin resistance (IR) (all p<0.01). GA prevented the rise in plasma glucose, insulin and triglycerides and improved insulin sensitivity. Tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) levels in plasma and the mRNA and protein levels of TNF-α and transforming growth factor-β1(TGF-β(1)) in liver were significantly higher in fructose-fed rats than control rats. However, treatment with GA downregulated the expression of these cytokines. Translocation of NF-κB into the nucleus was also increased in fructose diet-fed animals, which was prevented by GA. These results suggest that GA prevents oxidative damage and has a downregulatory effect on the inflammatory pathway in liver of fructose-fed rats.

Effect of seasonal variations and collection form on antioxidant activity of propolis from San Juan, Argentina

Propolis was included in the Argentine Food Code as a functional food. The chemical parameters and antioxidant properties of propolis samples from the same colonies of Apis mellifera in San Juan (Cuyo region, Western Argentine) were compared every month for 1 year using two collection methods. Chemical parameters were analyzed by the spectrophotometric method and fingerprinting using high-performance liquid chromatography with ultraviolet detection. The antioxidant activities of propolis samples were measured using model systems including the analysis of the scavenging activities for 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals and the beta-carotene bleaching assay. The results showed that propolis had a higher free radical scavenging and lipid peroxidation inhibitory capacity than butylated hydroxytoluene and quercetin, antioxidants used in the pharmaceutical and food industries. The concentration required to scavenge 50% of free radicals (SC(50)) values differed depending on the sample collection month. Samples collected in November had the highest antioxidant capacity. In all cases, SC(50) values of propolis samples obtained by scraping were similar to those collected from a wire mesh (5 microg/mL for ABTS and 20-30 microg/mL for DPPH radicals). A significant positive correlation was found between the antioxidant capacity and flavonoid content of each analyzed extract. The chemical profiles were very similar. Galangin (3,5,7-trihydroxyflavone), an antioxidant compound, was detected in all samples as a major compound. The chromatographic profile suggests that of Baccharis sp., which would be one of the botanical sources of propolis from western Argentina, and the content of galangin can be used as a parameter for evaluating propolis quality. Our results suggest that Argentine propolis from Cuyo is a promising source of bioactive compounds as ingredients for developing functional foods with a beneficial impact on oxidative stress.

Flavonoid galangin prevents smooth muscle fatigue of pig urinary bladder

There is increasing evidence that the generation of free radicals plays a role in the development of bladder dysfunction. Flavonoids are a group of polyphenolic compounds with broad pharmacological activity. In the present study, the protective effects of the flavonoid galangin on the progressive decrease of bladder smooth muscle contractile responses during repetitive field stimulation (RFS; a model for muscular fatigue) were demonstrated. Pig detrusor strips were mounted for tension recording in organ baths and were subjected to RFS for 90 min at 32 Hz for 15 s every 5 min. The strips were then washed four times with fresh buffer and allowed a period of recovery for 90 min. The 90 min of RFS caused a progressive decrease in maximal contractile response to electrical field stimulation and to muscarinic agonist-induced contractions (34% and 46% decrease, respectively). Galangin (10−7m) prevented the decrease in contractile smooth muscle response of strips to electrical field stimulation during RFS compared with untreated tissues. The antioxidant activity of galangin was assessed by measuring its ability to inhibit the lipid peroxidation induced by iron and ascorbate in rat liver microsomes (IC50 1.7 + 0.12 times 10−6m). If the data are confirmed in-vivo, exogenously administered galangin may be a new approach in the prevention and/or treatment of bladder dysfunction.

[Structure and function of peroxisomal tetrameric carbonyl reductase]

In this paper, the structure and function of a new tetrameric carbonyl reductase (TCR) is reviewed. TCRs were purified from rabbit and pig heart, using 4-benzoylpyridine as a substrate. Partial peptide sequencing and cDNA cloning of rabbit and pig TCRs revealed that both enzymes belonged to the short-chain dehydrogenase/reductase family and that their subunits consisted of 260 amino acid residues. Rabbit and pig TCRs catalyzed the reduction of alkyl phenyl ketones, alpha-dicarbonyl compounds, quinones and retinals. Both enzymes were potently inhibited by flavonoids and fatty acids. 9,10-Phenanthrenequinone, which is efficiently reduced by rabbit and pig TCRs, mediated the formation of superoxide radical through its redox cycling in pig heart. The C-terminal sequences of rabbit and pig TCRs comprised a type 1 peroxisomal targeting signal (PTS1) Ser-Arg-Leu, suggesting that the enzymes are localized in the peroxisome. In fact, pig TCR was targeted into the peroxisomal matrix, in the case of transfection of HeLa cells with vectors expressing the enzyme. However, when the recombinant pig TCR was directly introduced into HeLa cells, the enzyme was not targeted into the peroxisomal matrix. The crystal structure of recombinant pig TCR demonstrated that the C-terminal PTS1 of each subunit of the enzyme was buried in the interior of the tetrameric molecule. These findings indicate that pig TCR is imported into the peroxisome as a monomer and then forms an active tetramer within this organelle.

Inhibition of carbonyl reductase activity in pig heart by alkyl phenyl ketones

The inhibitory effects of alkyl phenyl ketones on carbonyl reductase activity were examined in pig heart. In this study, carbonyl reductase activity was estimated as the ability to reduce 4-benzoylpyridine to S(-)-alpha-phenyl-4-pyridylmethanol in the cytosolic fraction from pig heart (pig heart cytosol). The order of their inhibitory potencies was hexanophenone > valerophenone > heptanophenone > butyrophenone > propiophenone. The inhibitory potencies of acetophenone and nonanophenone were much lower. A significant relationship was observed between Vmax/Km values for the reduction of alkyl phenyl ketones and their inhibitory potencies for carbonyl reductase activity in pig heart cytosol. Furthermore, hexanophenone was a competitive inhibitor for the enzyme activity. These results indicate that several alkyl phenyl ketones including hexanophenone inhibit carbonyl reductase activity in pig heart cytosol, by acting as substrate inhibitors.

Flavonoids as protectors against doxorubicin cardiotoxicity: Role of iron chelation, antioxidant activity and inhibition of carbonyl reductase

Anthracycline antibiotics (e.g. doxorubicin and daunorubicin) are among the most effective and widely used anticancer drugs. Unfortunately, their clinical use is limited by the dose-dependent cardiotoxicity. Flavonoids represent a potentially attractive class of compounds to mitigate the anthracycline cardiotoxicity due to their iron-chelating, antioxidant and carbonyl reductase-inhibitory effects. The relative contribution of various characteristics of the flavonoids to their cardioprotective activity is, however, not known. A series of ten flavonoids including quercetin, quercitrin, 7-monohydroxyethylrutoside (monoHER) and seven original synthetic compounds were employed to examine the relationships between their inhibitory effects on carbonyl reduction, iron-chelation and antioxidant properties with respect to their protective potential against doxorubicin-induced cardiotoxicity. Cardioprotection was investigated in the neonatal rat ventricular cardiomyocytes whereas the H9c2 cardiomyoblast cells were used for cytotoxicity testing. Iron chelation was examined via the calcein assay and antioxidant effects and site-specific scavenging were quantified by means of inhibition of lipid peroxidation and hydroxyl radical scavenging activity, respectively. Inhibition of carbonyl reductases was assessed in cytosol from human liver. None of the flavonoids tested had better cardioprotective action than the reference cardioprotector, monoHER. However, a newly synthesized quaternary ammonium analog with comparable cardioprotective effects has been identified. No direct correlation between the iron-chelating and/or antioxidant effect and cardioprotective potential has been found. A major role of carbonyl reductase inhibition seems unlikely, as the best two cardioprotectors of the series are only weak reductase inhibitors.

Chemical structure of flavonols in relation to modulation of angiogenesis and immune-endothelial cell adhesion

The antioxidant activity of flavonoids has been suggested to contribute to several health benefits associated with the consumption of fruits and vegetables. Four flavonols - myricetin (M), quercetin (Q), kaempferol (K) and galangin (G), all with different numbers of hydroxyl moieties (-OH) - were examined for their antioxidant activity and cytotoxicity on human umbilical vein endothelial cells (HUVECs) and for their potential antiangiogenic and cell adhesion effects. The relative antioxidant capacity of these flavonols in cell culture medium (cell-free system) and their intracellular antioxidant activity were M = Q > K = G, which correlated respectively with the presence of 3, 2, 1 and 0 moieties of -OH on their B-ring. The higher the numbers of -OH moieties on the B-ring the less toxic the flavonol was to HUVEC, and the LD50 was determined as: M (100 microM) > Q (50 microM) > K (20 microM) > G (10 microM). These flavonols at approximately 0.5 LD50 doses suppressed the vascular endothelial growth factor (VEGF)-stimulated HUVEC tubular structure formation by: M (47%) > Q (37%) > K (15%) > G (14%), which was not linearly associated with their numbers of -OH moieties. However, the magnitude of flavonols' suppression of activated U937 monocytic cells adhesion to HUVEC was associated with the number of -OH moieties on the B-ring. This was prominent when U937 cells were pretreated with these flavonols. In contrast, the numbers of -OH moiety had no apparent influence on the adhesion or expression of adhesion molecules when activated HUVECs were pretreated with these flavonols. The presence of different numbers of -OH moieties on the B-ring of the flavonols may contribute to their antioxidant activity as well as their toxicity and may play an important role in their potency for biological action such as angiogenesis and immune-endothelial cell adhesion, which, respectively, are important processes in the development of cancer and atherosclerosis.

Aldehyde sources, metabolism, molecular toxicity mechanisms, and possible effects on human health

Aldehydes are organic compounds that are widespread in nature. They can be formed endogenously by lipid peroxidation (LPO), carbohydrate or metabolism ascorbate autoxidation, amine oxidases, cytochrome P-450s, or myeloperoxidase-catalyzed metabolic activation. This review compares the reactivity of many aldehydes towards biomolecules particularly macromolecules. Furthermore, it includes not only aldehydes of environmental or occupational concerns but also dietary aldehydes and aldehydes formed endogenously by intermediary metabolism. Drugs that are aldehydes or form reactive aldehyde metabolites that cause side-effect toxicity are also included. The effects of these aldehydes on biological function, their contribution to human diseases, and the role of nucleic acid and protein carbonylation/oxidation in mutagenicity and cytotoxicity mechanisms, respectively, as well as carbonyl signal transduction and gene expression, are reviewed. Aldehyde metabolic activation and detoxication by metabolizing enzymes are also reviewed, as well as the toxicological and anticancer therapeutic effects of metabolizing enzyme inhibitors. The human health risks from clinical and animal research studies are reviewed, including aldehydes as haptens in allergenic hypersensitivity diseases, respiratory allergies, and idiosyncratic drug toxicity; the potential carcinogenic risks of the carbonyl body burden; and the toxic effects of aldehydes in liver disease, embryo toxicity/teratogenicity, diabetes/hypertension, sclerosing peritonitis, cerebral ischemia/neurodegenerative diseases, and other aging-associated diseases.

Vasorelaxant effect of the flavonoid galangin on isolated rat thoracic aorta

Here we investigated the effect of the flavonoid galangin in isolated rat thoracic aortic rings. Galangin (0.1-100 microM) induced relaxation in rings pre-contracted with phenylephrine (PE 1 microM) or with KCl (100 mM) or pre-treated with the nitric oxide synthase inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME, 100 microM), the cyclooxygenase inhibitor indomethacin (10 microM) and the adenylate cyclase inhibitor, SQ 22,536 (100 microM). In another set of experiments, rat aortic rings were incubated with galangin (1-100 microM) and the contractile responses to PE (0.001-3 microM) or to KCl (60 mM) were evaluated. We also evaluated the effect of galangin (100 microM) on PE (10 microM)-induced contraction in a Ca2+-free medium. Galangin relaxed aortic rings with or without endothelium. Galangin effect was significantly inhibited by L-NAME. Galangin inhibited the contractile response to PE, either in presence or in absence of external calcium, and to KCl. In the end, we also found that galangin caused nitric oxide (NO) release from aortic rings and abolished the increase in [Ca2+]i triggered by PE or KCl in aortic smooth muscle cells, either in presence and in absence of external Ca2+. Our results suggest that galangin reduces the contractility of rat aortic rings through an endothelium-dependent mechanism, involving NO, and also through an endothelium-independent mechanism, inhibiting calcium movements through cell membranes.

Galangin protects pig detrusor nerves from repetitive field stimulation and anoxia/glucopenia injury

OBJECTIVES

To test the capability of the flavonoid galangin to protect pig urinary bladder from damage due to a period of repetitive field stimulation as well as a period of anoxia/glucopenia and reperfusion.

METHODS

Smooth muscle strips of the pig bladder were mounted for tension recording in small organ baths and the strips underwent either 1.5 hours of repetitive field stimulation at 32 Hz for 15 seconds every 5 minutes or under anoxia/glucopenia and reperfusion conditions. Galangin, at different concentrations, was added to the reperfusion Krebs solution to check the effect of this flavonoid compared with untreated strips under the same conditions. A group of experiments was performed to examine its possible underlying mechanisms.

RESULTS

Repetitive field stimulation for 1.5 hours caused a progressive decrease in the maximal contractile response to electrical field stimulation (34% decrease). Galangin (10(-7) M) partially prevented the progressive decrease in the contractile response. This effect was significantly reduced when verapamil was added to the solution. Galangin significantly improved the response of strips to electrical field stimulation under anoxia/glucopenia and reperfusion conditions compared with untreated tissues.

CONCLUSIONS

Galangin has a protective effect on bladder contractility by an action that at least, in part, depends on l-type calcium channels. Furthermore, galangin protects detrusor nerves against the anoxia/glucopenic and reperfusion damage.

A proteomics approach to identify changes in protein profiles in pre-cancerous colon

The development of colon cancer is characterised by alterations in multiple genetic and epigenetic pathways in colon tissue leading ultimately to deregulation of colon epithelial cells. Early detection is an important factor in decreasing colon cancer deaths. Proteomic techniques were used to identify potential early markers in colon tissue exhibiting pre-cancerous activity that may characterise pathological changes in a chemically induced colon cancer rat model. Protein profiles were assessed in soluble and insoluble fractions prepared from distal colon of rats treated with the colonotropic carcinogen, dimethylhydrazine. Alterations in protein profiles were associated with the presence of aberrant crypt foci, hyperplasia and dysplasia, microanatomical changes, and metabolic changes in rat colon. These changes may have a potential role in the identification of pre-pathological features preceding colon tumorigenesis.

Inhibitory effects of flavonoids on the reduction of progesterone to 20alpha-hydroxyprogesterone in rat liver

The first aim of this study is to characterize the reduction of progesterone in rat liver. Progesterone was mainly reduced to 20alpha-hydroxyprogesterone in the cytosolic fraction of rat liver. The amount of 20alpha-hydroxyprogesterone formed from progesterone in the cytosolic fraction was significantly larger in the males than in the females and this enzyme reaction proceeded not only in the presence of NADPH, but also in the presence of NADH. Furthermore, we attempted to evaluate the inhibitory effects of 15 flavonoids on the NADPH-dependent reduction of progesterone to 20alpha-hydroxyprogesterone in liver cytosol of male rats. The order of the inhibitory potencies was luteolin>apigenin>quercetin>myricetin=fisetin=kaempferol. Other flavonoids exhibited lower inhibitory potencies. Energy-minimized molecular models demonstrated that a planar benzopyrone ring (A and C rings) with a coplanar phenyl ring (B ring) is a structural characteristic determining the inhibitory effects of flavonoids other than isoflavones.

Inhibitory effect of the plant flavonoid galangin on rat vas deferens in vitro

Flavonoids are phenolic compounds that are widely distributed in higher plants and therefore are ingested by humans and animals with their regular foods, but also have various pharmacological properties. In the present study we have investigated the effect of galangin, a member of the flavonol class, on the contractile response elicited by electrical field stimulation (EFS) in the rat isolated vas deferens. Galangin (10(-8)-3 x 10(-4) M) produced a concentration- dependent inhibition of the EFS-evoked contractile response, with only a minimal inhibitory effect on phenylephrine-induced contractions. The inhibitory effect of galangin was unaffected by atropine (10(-6) M) plus hexamethonium (10(-4) M), a combination of the NK(1) receptor antagonist SR 140333 (10(-7) M), the NK(2) receptor antagonist SR 48968 (10(-6) M) and the NK(3) receptor antagonist SR 142801 (10(-7) M), L-NAME (3 x 10(-4) M), naloxone (10(-6) M) or yohimbine (10(-7) M). However, the vanilloid receptor antagonist capsazepine (10(-5) M) significantly reduced the inhibitory effect of galangin. It is concluded that the galangin inhibits excitatory transmission of the rat vas deferens with a mechanism involving, at least in part, vanilloid receptors.

Cloning, expression and tissue distribution of a tetrameric form of pig carbonyl reductase

In this study, we isolated a cDNA for tetrameric carbonyl reductase (CR) from pig heart. The pig CR showed high amino acid sequence identity (81%) with rabbit NADP(+)-dependent retinol dehydrogenase (NDRD). The purified recombinant pig CR and NDRD were about 100-kDa homotetramers and exhibited high reductase activity towards alkyl phenyl ketones, alpha-dicarbonyl compounds and all-trans-retinal. The identity of NDRD with the tetrameric CR was verified by protein sequencing of CR purified from rabbit heart. Both tetrameric CR and its mRNA were ubiquitously expressed in pig and rabbit tissues. The pig and rabbit enzymes belonged to the short-chain dehydrogenase/reductase family, and their sequences comprise a C-terminal SRL tripeptide, which is a variant of the type 1 peroxisomal targeting signal, SKL. Transfection of HeLa cells with vectors expressing pig CR demonstrated that the enzyme is localized in the peroxisomes. Thus, the tetrameric form of CR represents the first mammalian peroxisomal enzyme that reduces all-trans-retinal as the endogenous substrate.

Effect of the flavonoid galangin on urinary bladder rat contractility in-vitro

Galangin is a flavanol with several biological activities. We have evaluated the effect of galangin on the contractile response elicited by electrical field stimulation (EFS) in the rat isolated urinary bladder. Galangin (10(-8)-10(-4) M) produced a concentration-dependent inhibition of the EFS contractile response without modifying the contractions produced by exogenous acetylcholine (10(-6) M). Blockade of adrenergic and cholinergic nerves with a combination of atropine (10(-6) M), phentolamine (10(-6) M) and propranolol (10(-6) M) or blockade of tachykinin NK1 and NK2 receptors with SR140333 (10(-7) M) and SR48968 (10(-6) M) did not modify the inhibitory effect of galangin. However, verapamil (10(-7) M) significantly reduced the inhibitory effect of galangin. It is concluded that the galangin inhibits EFS-induced contractions of the rat urinary bladder by acting on L-type calcium channels on presynaptic nerves.

Anti-genotoxicity of galangin as a cancer chemopreventive agent candidate

Flavonoids are polyphenolic compounds that are present in plants. They have been shown to possess a variety of biological activities at non-toxic concentrations in organisms. Galangin, a member of the flavonol class of flavonoid, is present in high concentrations in medicinal plants (e.g. Alpinia officinarum) and propolis, a natural beehive product. Results from in vitro and in vivo studies indicate that galangin with anti-oxidative and free radical scavenging activities is capable of modulating enzyme activities and suppressing the genotoxicity of chemicals. These activities will be discussed in this review. Based on our review, galangin may be a promising candidate for cancer chemoprevention.