RESUMO
The food industry is constantly attempting to develop better products that will have a positive effect on health. Feiraco® and Clesa®, expressed their intention to create novel products using UNICLA® milk as a matrix to develop functional foods. In this respect, ß-cyclodextrin (ß-CD) at 1% was able to reduce the cholesterol concentration in Feiraco-UNICLA® milk products by around 87-85%. Products were fortified with omega-3 from fish oil with α- and ß-CD acting as carriers. It was possible to add around 50% of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) Recommended Dietary Allowances (RDA), with a high diet proportion of fibre and similar organoleptic properties to commercial omega-3 products. 80% of a sensory panel found our formulations satisfactory. The final product was stable, and the bioaccessibilty of the fatty acids added to the milk was around 74%. These results as a whole satisfy the aid of Feiraco® and Clesa® to develop improved products.
Assuntos
Ciclodextrinas , Ácidos Graxos Ômega-3 , Doenças Metabólicas , Animais , Ácidos Docosa-Hexaenoicos/metabolismo , Ácido Eicosapentaenoico , Ácidos Graxos , Ácidos Graxos Ômega-3/metabolismo , Óleos de Peixe , Humanos , Leite/metabolismo , IogurteRESUMO
Androgenetic alopecia (AGA), a hair loss disorder, is a genetic predisposition to sensitive androgens, inflammation, and oxidative stress. Unfortunately, current treatments with synthetic medicines contain a restricted mechanism along with side effects, whereas the bioactive constituents of plant extracts are multifunctional, with fewer side effects. The massive amounts of rice husk and bran are agricultural wastes that may cause pollution and environmental problems. Owing to these rationales, the local rice variety, Bue Bang 3 CMU (BB3CMU), which is grown in northern Thailand, was evaluated for the valuable utilization of rice by-products, husk (BB3CMU-H) and bran (BB3CMU-RB) extracts, for AGA treatment regarding antioxidant, anti-inflammatory, anti-androgenic activities, and the characterization of bioactive compounds. Our study verified that BB3CMU-H had the highest level of polyphenols, contributing to its greater antioxidant activity. Conversely, BB3CMU-RB was the predominant source of tocopherols, resulting in better anti-androgenic activities regarding the downregulation of steroid 5α-reductase genes (SRD5A). Notably, anti-inflammation via the attenuation of nitric oxide productions was observed in BB3CMU-H (0.06 ± 0.13 µM) and BB3CMU-RB (0.13 ± 0.01 µM), which were significantly comparable to diclofenac sodium salt (0.13 ± 0.19 µM). Therefore, the combination of BB3CMU-H and BB3CMU-RB could be utilized in cosmeceutical and pharmaceutical applications for AGA patients.
RESUMO
The potential of naturally occurring polyphenols as nutraceuticals to prevent and/or treat Alzheimer's disease is studied. Five structurally related flavones and four tyrosols were tested in vitro in human amyloid-ß peptide aggregation assays. The most promising compounds were two flavones, scutellarein and baicalein, and two tyrosols hydroxytyrosol and hydroxytyrosol acetate. These compounds caused a dose-dependent reduction of Aß-peptide aggregation up to 90% for the flavones and 100% for the tyrosols, at concentrations of 83.3 µM and 33.3 mM, respectively. The IC50 value obtained for scutellarein was 22.5 µM, and was slightly higher for baicalein, 25.9 µM, while for hydroxytyrosol and hydroxytyrosol acetate they were 0.57 mM and 0.62 mM. Given these results, the compounds were selected to conduct in vivo assays with the Caenorhabditis elegans animal model of Alzheimer's disease. The amyloid anti-aggregation ability of these polyphenols was demonstrated in in vivo aggregation assays in which 1 mM hydroxytyrosol reduced the amyloid plaques in the mutant strain CL2331 by 43%. The neuroprotective effect was evaluated in chemotaxis experiments carried out with transgenic strain CL2355 that expresses the human amyloid-ß peptide in the neurons. The chemotaxis index was improved by 240% when the neuron-impaired animals were treated with 1 mM hydroxytyrosol. The results indicate that the four molecules would be viable candidates to develop nutraceuticals that interfere in amyloid-ß peptide aggregation and, consequently, prevent and/or treat Alzheimer's disease.
Assuntos
Peptídeos beta-Amiloides/metabolismo , Dieta Mediterrânea , Medicina Tradicional Chinesa/métodos , Polifenóis/metabolismo , Polifenóis/farmacologia , Animais , Caenorhabditis elegans , Modelos Animais de Doenças , HumanosRESUMO
In this work, the increase of the Caenorhabditis elegans (C. elegans) lifespan extension using hyper-branched cyclodextrin-based nanosponges (CD-NS) complexing oxyresveratrol (OXY), and the possible inhibition of C. elegans phosphodiesterase type 4 (PDE4) were evaluated. The titration displacement of fluorescein was used to calculate the apparent complexation constant (KF) between CD-NS and OXY. Moreover, PDE4 was expressed in E. coli, purified and refolded in presence of cyclodextrins (CDs) to study its possible inhibition as pharmacological target of OXY. The apparent activity was characterized and the inhibitory effect of OXY on PDE4 displayed a competitive in vitro inhibition corroborated in silico. A maximum increase of the in vivo life expectancy of about 9.6% of using OXY/CD-NS complexes in comparison with the control was obtained, in contrast to the 6.5% obtained with free OXY. No effect on lifespan or toxicity with CD-NS alone was found. These results as a whole represent new opportunities to use OXY and CD-NS in lifespan products.
Assuntos
Ciclodextrinas , Animais , Caenorhabditis elegans , Suplementos Nutricionais , Escherichia coli , Longevidade , Extratos Vegetais , EstilbenosRESUMO
The complexation of the bioactive compound oxyresveratrol (OXY) with a polymer called cyclodextrin-based nanosponge (CD-NS) and its application was studied.A new methodology is used to calculate, an apparent inclusion complex constant (KFapp) between a ligand and CD-NSs. Moreover, the KFapp of resveratrol was also evaluated and compared. The complex of OXY with the nanosponge ß-CDI 1:4, was studied in vitro using DSC, TGA and FTIR techniques and its drug loading and release behavior were studied. An in vitro digestion showed higher protection of OXY complexed than free OXY. The bioactivity enhancing capacity of OXY was also studied against prostate (PC-3) and colon (HT-29 and HCT-116) cancer cell lines, where it showed stronger cell viability inhibition than the free drug. The findings as a whole represent a new opportunity for studying the complexation of drugs in CD-NSs and the use of oxyresveratrol as an ingredient in nutraceutical products.
Assuntos
Antineoplásicos/química , Nanoestruturas/química , Extratos Vegetais/farmacologia , Estilbenos/farmacologia , beta-Ciclodextrinas/química , Antineoplásicos/farmacologia , Neoplasias do Colo/tratamento farmacológico , Células HCT116 , Humanos , Masculino , Extratos Vegetais/química , Polímeros/química , Neoplasias da Próstata/tratamento farmacológico , Solubilidade , Estilbenos/química , Temperatura , beta-Ciclodextrinas/farmacologiaRESUMO
Betalains are nitrogenous plant pigments known for their high antioxidant capacity. For the first time, this antioxidant nature has been studied in an in vivo system using the model organism Caenorhabditis elegans. The oxidative stress caused in the fluorescent strain TJ375 (hsp-16.2::GFP) was reversed by the presence of both natural and semi-synthetic betalains, with an ED50 value around 25⯵M for betacyanins and up to 10⯵M for betaxanthins, with indicaxanthin, the major pigments in prickly pear fruits, as the most effective betalain. The effect of model betalains on the lifespan of the wild-type N2 strain was carefully studied using the automatic platform "Lifespan Machine". In a search for different approaches to suppress progeny, pop-1 RNAi was used to avoid FUdR use. The presence of betalains in the medium, both as pure compounds and as enriched Opuntia extracts significantly increased the lifespan of C. elegans.
Assuntos
Antioxidantes/farmacologia , Betalaínas/farmacologia , Caenorhabditis elegans/efeitos dos fármacos , Opuntia/química , Extratos Vegetais/farmacologia , Animais , Animais Geneticamente Modificados , Betacianinas/farmacologia , Betalaínas/química , Betalaínas/farmacocinética , Betaxantinas/farmacologia , Caenorhabditis elegans/genética , Caenorhabditis elegans/fisiologia , Frutas/química , Longevidade , Estresse Oxidativo/efeitos dos fármacos , Piridinas/farmacologia , Interferência de RNARESUMO
OBJECTIVE: To assess the impact of an antioxidant preparation with N-acetyl cysteine, alpha lipoic acid and bromelain on endometriosis-associated pelvic pain. STUDY DESIGN: Multicenter, open-label, non-comparative clinical trial in a representative sample of women with endometriosis-associated pelvic pain. RESULTS: In total, 398 patients with a mean age of 34.6⯱â¯7.2 years were treated with a combination of N-acetyl cysteine, alpha lipoic acid and bromelain for 6 months. At baseline, 92.7% of the patients had pain intensity > 4 on the visual analogue scale (VAS); at 3 months of treatment, this percentage decreased to 87.2% (pâ¯=â¯0.074) and at 6 months the percentage was 82.7% (pâ¯<â¯0.05). CONCLUSIONS: Women with endometriosis who wish to become pregnant and are treated with a preparation containing N-acetyl cysteine, alpha lipoic acid and bromelain experienced a significant improvement in endometriosis-associated pelvic pain and required lower intake of rescue analgesics.
Assuntos
Acetilcisteína/uso terapêutico , Antioxidantes/uso terapêutico , Bromelaínas/uso terapêutico , Endometriose/complicações , Dor Pélvica/tratamento farmacológico , Ácido Tióctico/uso terapêutico , Adulto , Combinação de Medicamentos , Feminino , Humanos , Dor Pélvica/etiologia , GravidezRESUMO
The food industry needs cheap, fast and sensitive methods to increase the number of analyses that are routinely carried out; for this reason, new methods are constantly being sought. This paper describes a novel fluorescent nanosensor based on cyclodextrin (CD) to determine ellagic acid (EA). The encapsulation of EA in the presence of borax was studied. Firstly, the complexation of EA-borax was tested. The stoichiometry of the EA-borax complex showed a 1 : 2 complex, with KF1 = 2548 ± 127 M-1 and KF2 = 302 ± 15 M-1. Different CDs were used to obtain a 1 : 1 : 1 CD-EA-borax complex with γ-CD providing the best complexation constant (KF3 = 364 ± 18 M-1). Furthermore, when the accuracy and sensitivity of the nanosensor were tested using a crude blueberry extract, the CD/borax mixture provided an 18 times stronger signal than with the crude extract alone and 7 times stronger than that obtained using borax alone.
Assuntos
Técnicas Biossensoriais/métodos , Boratos/química , Ácido Elágico/química , Análise de Alimentos/métodos , Extratos Vegetais/química , Técnicas Biossensoriais/instrumentação , Mirtilos Azuis (Planta)/química , Ciclodextrinas/química , Fluorescência , Análise de Alimentos/instrumentação , Frutas/química , Concentração de Íons de Hidrogênio , TemperaturaRESUMO
Betalains are natural pigments characteristic of plants of the order Caryophyllales. In this work, the role of betalains in the anti-inflammatory activity described for plant extracts is analysed in terms of the inactivation of the enzymes involved in the biochemical response (lipoxygenase and cyclooxygenase). Pure natural betalains and semi-synthetic analogues are demonstrated to promote a significant reduction of the enzymes activity. Reactions were followed spectrophotometrically and by HPLC-DAD. Phenethylamine-betaxanthin was the most potent in the inactivation of cyclooxygenase, with a reduction of 32% of the control activity at 125µM, while the natural pigment betanidin and a betalain analogue derived from indoline resulted as the most potent inactivators of lipoxygenase, with IC50 values of 41.4 and 40.1µM, respectively. Molecular docking studies revealed that betalains interact with the lipoxygenase amino acids involved in substrate binding and with Tyr-385 and Ser-530 close to the cyclooxygenase active site, interfering in enzyme catalysis.
Assuntos
Betalaínas/química , Inibidores de Ciclo-Oxigenase/química , Inibidores de Lipoxigenase/química , Lipoxigenase/química , Extratos Vegetais/química , Prostaglandina-Endoperóxido Sintases/química , Beta vulgaris/química , Betalaínas/síntese química , Inibidores de Ciclo-Oxigenase/síntese química , Ativação Enzimática , Humanos , Cinética , Inibidores de Lipoxigenase/síntese química , Simulação de Acoplamento Molecular , Estrutura Molecular , Extratos Vegetais/síntese químicaRESUMO
In recent years, the growth of the functional foods industry has increased research into new compounds with high added value for use in the fortification of traditional products. One of the most promising functional food groups is those enriched in antioxidant compounds of a lipophilic nature. In spite of the numerous advantages reported for such antioxidant molecules, they may also have disadvantages that impede their use in functional foods, although these problems may well avoided by the use of encapsulant agents such as cyclodextrins. This explains the recent increase in the number of research papers dealing with the complexation of different guest molecules possesing important antioxidant properties using natural and modified cyclodextrins. This paper presents a review of the most recent studies on the complexes formed between several important types of antioxidant compounds and cyclodextrins, focusing on the contradictory data reported in the literature concerning to the antioxidant activity of the host/guest molecule complexes, the different complexation constants reported for identical complexes, the bioavailability of the antioxidant compound in the presence of cyclodextrins and recommendation concerning the use of natural or modified cyclodextrins. Moreover, the use of cyclodextrins as antibrowning agents to prevent enzymatic browning in different foods is revised. Finally, we look at studies which suggest that cyclodextrins act as ''secondary antioxidants," enhancing the ability of traditional antioxidants to prevent enzymatic browning.
Assuntos
Antioxidantes , Ciclodextrinas , Alimento Funcional , Antioxidantes/química , Antioxidantes/farmacocinética , Antioxidantes/farmacologia , Disponibilidade Biológica , Carotenoides , Ciclodextrinas/química , Ciclodextrinas/farmacocinética , Ciclodextrinas/farmacologia , Dieta , Suplementos Nutricionais , Ácidos Graxos , Indústria Alimentícia , Humanos , Reação de Maillard/efeitos dos fármacos , Resveratrol , Amido/química , Estilbenos , Ubiquinona/análogos & derivados , VitaminasRESUMO
Betalains are water-soluble pigments with high antiradical capacity which bestow bright colors to flowers, fruits and other parts of most plants of the order Caryophyllales. The formation of the structural unit of all betalains, betalamic acid from the precursor amino acid 4,5-dihydroxyphenylalanine is catalyzed by the enzyme 4,5-DOPA-extradiol-dioxygenase followed by intramolecular cyclization of the 4,5-secodopa intermediate. This paper describes the purification and the molecular and functional characterization of an active 4,5-DOPA-extradiol-dioxygenase from the best-known source of betalains-Beta vulgaris-after heterologous expression in Escherichia coli. The enzyme is a monomeric protein with a molecular mass of 32 kDa characterized by chromatography, electrophoresis and MALDI-TOF analysis. Enzyme kinetic properties are characterized in the production of betalamic acid, the structural, chromophoric and bioactive unit of plant pigment betalains.
Assuntos
Beta vulgaris/enzimologia , Betalaínas/metabolismo , Dioxigenases/metabolismo , Oxigenases/isolamento & purificação , Pigmentos Biológicos/biossíntese , Proteínas de Plantas/metabolismo , Beta vulgaris/genética , Regulação Enzimológica da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Proteínas RecombinantesRESUMO
In this work, a reversed phase high performance liquid chromatography (RP-HPLC) method was developed for the determination of pterostilbene in food samples. The novel method is based on the addition of cyclodextrins (CDs) to the mobile phase where the complexation of pterostilbene by CDs is carried out. In order to select the most suitable conditions for the RP-HPLC method, the effect of several physico-chemical parameters on the complexation of pterostilbene by CDs was studied. Our results show that the addition of 12 mM HP-ß-CD to a 50:50 (v/v) methanol:water mobile phase at 25°C and pH 7.0 significantly improves the main analytical parameters. In addition, it was seen that pterostilbene forms a 1:1 complex with HP-ß-CD, showing an apparent complexation constant of 251±13 M(-1). Finally, in order to study the validity of the proposed method, blueberries were analyzed and the concentration of pterostilbene has been determined.
Assuntos
Mirtilos Azuis (Planta)/química , Cromatografia de Fase Reversa/métodos , Estilbenos/análise , beta-Ciclodextrinas/química , 2-Hidroxipropil-beta-Ciclodextrina , Cromatografia Líquida de Alta Pressão/métodos , Concentração de Íons de Hidrogênio , Modelos Lineares , Extratos Vegetais/análise , Extratos Vegetais/química , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Estilbenos/química , Temperatura , ÁguaRESUMO
Knowledge of the complexation process of oxyresveratrol with beta-cyclodextrin (beta-CD) under different physicochemical conditions is essential if this potent antioxidant compound is to be used successfully in both food and pharmaceutical industries as ingredient of functional foods or nutraceuticals, despite its poor stability and bioavailability. In this paper, the complexation of oxyresveratrol with natural CDs was investigated for first time using RP-HPLC and mobile phases to which alpha-, beta-, and gamma-CD were added. Among natural CDs, the interaction of oxyresveratrol with beta-CD was more efficient than with alpha- and gamma-CD. The decrease in the retention times with increasing concentrations of beta-CD (0-4 mM) showed that the formation constants (KF) of the oxyresveratrol/beta-CD complexes were strongly dependent on both the water-methanol proportion and the temperature of the mobile phase employed. However, oxyresveratrol formed complexes with beta-CD with a 1:1 stoichiometry in all the physicochemical conditions tested. Moreover, to obtain information about the mechanism of the oxyresveratrol affinity for beta-CD, the thermodynamic parameters DeltaG degrees, DeltaH degrees and DeltaS degrees were obtained. Finally, to gain information on the effect of the structure of different compounds belonging to the stilbenoids family on the KF values, the complexation of other molecules, resveratrol, pterostilbene and pinosylvin, was studied and compared with the results obtained for the oxyresveratrol/beta-CD complexes.
Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Cromatografia de Fase Reversa/métodos , Extratos Vegetais/química , Estilbenos/química , beta-Ciclodextrinas/química , Metanol , Temperatura , Termodinâmica , ÁguaRESUMO
Free radical scavenging compounds play important roles as health-protecting factors. Betalains are natural water-soluble pigments present in most plant families belonging to the order Caryophyllales. They are the subject of increasing attention following the discovery of their antiradical capacity, but a systematic analysis of the structural features involved in the activity is necessary. In this paper, both natural and previously unconsidered betaxanthins were obtained in order to study the role of phenolic hydroxy groups in the high free radical scavenging activity of betalains. Pigments were characterized spectrophotometrically, chromatographically, and by ESI-MS, and their antiradical and antioxidant properties were studied under the ABTS(*+) radical and FRAP assays. A high intrinsic activity is described that is not linked to the presence of hydroxy groups or aromaticity in the pigment structure. In addition, the presence of phenolic hydroxy groups implies an enhancement of the antiradical activity, reaching a TEAC value in the ABTS(*+) assay of 5.8 +/- 0.2 for the pure compound with two hydroxy groups.
Assuntos
Antioxidantes/isolamento & purificação , Antioxidantes/farmacologia , Betalaínas/isolamento & purificação , Betalaínas/farmacologia , Caryophyllaceae/química , Sequestradores de Radicais Livres/isolamento & purificação , Sequestradores de Radicais Livres/farmacologia , Fenóis/química , Fenóis/farmacologia , Plantas Medicinais/química , Antioxidantes/química , Betalaínas/química , Flores/química , Sequestradores de Radicais Livres/química , Concentração de Íons de Hidrogênio , Estrutura Molecular , Pigmentos Biológicos/fisiologia , Relação Estrutura-AtividadeRESUMO
The way flowers appear to insects is crucial for pollination. Here we describe an internal light-filtering effect in the flowers of Mirabilis jalapa, in which the visible fluorescence emitted by one pigment, a yellow betaxanthin, is absorbed by another, a violet betacyanin, to create a contrasting fluorescent pattern on the flower's petals. This finding opens up new possibilities for pollinator perception as fluorescence has not previously been considered as a potential signal in flowers.
Assuntos
Flores/química , Flores/efeitos da radiação , Fluorescência , Nyctaginaceae/química , Nyctaginaceae/efeitos da radiação , Animais , Betacianinas , Cromatografia Líquida de Alta Pressão , Cor , Indóis/análise , Indóis/química , Indóis/isolamento & purificação , Indóis/efeitos da radiação , Insetos/fisiologia , Luz , Modelos Biológicos , Ácidos Picolínicos/análise , Ácidos Picolínicos/química , Ácidos Picolínicos/isolamento & purificação , Ácidos Picolínicos/efeitos da radiação , Pigmentação , Pigmentos Biológicos/análise , Pigmentos Biológicos/química , Pigmentos Biológicos/isolamento & purificação , Pigmentos Biológicos/efeitos da radiação , Pólen/fisiologiaRESUMO
A kinetic study of the activity of soluble and membrane-bound latent polyphenol oxidase (PPO) extracted from beet root (Beta vulgaris) was carried out. For the first time, two types of behavior (hyperbolic and sigmoid) are reported in the same enzyme for PPO activation by the surfactant sodium dodecyl sulfate (SDS), depending on substrate nature. A kinetic model based on cooperative systems is developed to describe the activation effect of SDS, enabling the determination of the number of surfactant molecules binding to the enzyme in the activation process. The results indicate that the active site of the enzyme is not affected by SDS and that a stepwise conformational change favors the access of hydrophobic substrates compared to hydrophilic ones. Differential activation of PPO mediated by SDS may be of relevance in the control of PPO activity since the enzyme is able to express activity toward a specific substrate while remaining latent to others.
Assuntos
Beta vulgaris/enzimologia , Catecol Oxidase/metabolismo , Dodecilsulfato de Sódio/farmacologia , Ativação Enzimática/efeitos dos fármacos , Concentração de Íons de Hidrogênio , Cinética , Raízes de Plantas/enzimologiaRESUMO
PURPOSE: To compare intraoperative pain scores and objective stress signs during clear corneal phacoemulsification under cryoanalgesia and topical anesthesia. SETTING: Hospital Ramón y Cajal, Madrid, and Hospital Universitario Nuestra Sra. de la Candelaria, Tenerife, Canary Islands, Spain. METHODS: Eighty-two patients were randomized to have phacoemulsification under cryoanalgesia or topical anesthesia. Uncooperative patients and those with shallow anterior chamber and small pupils were excluded. In case of breakthrough pain during the surgery, a supplemental anesthesia protocol was established. Each patient was asked to grade the severity of pain on a 4-point scale (verbal description score; 0=none, 1=little, 2=some, or 3=much). Immediately after surgery, the general discomfort and pain were evaluated. Surgeon stress was evaluated during surgery. A comparison of the 2 groups was performed using a statistical analysis of variance. RESULTS: Supplemental anesthesia was required in 1 patient in each group. A total of 95.23% of patients would repeat the same technique under cryoanalgesia versus 97.5% under topical anesthesia. Similar pain levels and surgical stress scores were noted in both groups. CONCLUSIONS: Cryoanalgesia clear corneal phacoemulsification was safe with an acceptable level of pain. It induced a physiological stress response to that of topical anesthesia (blood pressure and heart rate). Cryoanalgesia was preferred over topical anesthesia by some patients. It is a suitable technique for anesthetic allergy cases.
Assuntos
Analgesia/métodos , Anestesia Local/métodos , Córnea/cirurgia , Crioanestesia/métodos , Implante de Lente Intraocular , Facoemulsificação , Adulto , Idoso , Idoso de 80 Anos ou mais , Anestésicos Combinados/administração & dosagem , Anestésicos Locais/administração & dosagem , Dor Ocular/diagnóstico , Dor Ocular/prevenção & controle , Feminino , Humanos , Complicações Intraoperatórias , Lentes Intraoculares , Masculino , Pessoa de Meia-Idade , Medição da Dor , Dor Pós-Operatória/diagnóstico , Dor Pós-Operatória/prevenção & controle , Satisfação do Paciente , Estudos Prospectivos , Pseudofacia/fisiopatologia , Método Simples-Cego , Estresse Psicológico/prevenção & controle , Inquéritos e Questionários , Acuidade Visual/fisiologiaRESUMO
Polyphenol oxidase (PPO) was extracted from beet root, in both soluble and membrane fractions, and in both cases the enzyme was in a latent state. PPO from the membrane fraction showed no diphenolase activity unless it was activated by trypsin or sodium dodecyl sulfate (SDS). The kinetics of the activation process of latent PPO by trypsin was studied and the specific rate constant of active PPO formation, k 3 , showed a value of 0.03 s(-1). The protease-activated form showed a pH optimum (6.5) and kinetic properties identical to those of the SDS-activated enzyme. Evidence is provided for the existence of a common peptide responsible for the regulation of the activity of the enzyme by both proteolysis and SDS detergent. Formation of the active proteolyzate was followed by spectroscopic measurements, Western blotting and partially denaturing SDS-PAGE.
Assuntos
Beta vulgaris/enzimologia , Catecol Oxidase/metabolismo , Dodecilsulfato de Sódio , Tripsina/farmacologia , Western Blotting , Catecol Oxidase/química , Eletroforese em Gel de Poliacrilamida , Ativação Enzimática/efeitos dos fármacos , Concentração de Íons de Hidrogênio , Cinética , Raízes de Plantas/enzimologiaRESUMO
Polyphenol oxidase (PPO) has been extracted from beet root, in both soluble and membrane fractions. In both cases, the enzyme was in its latent state, and it was activated by sodium dodecyl sulfate. PPO was purified to apparent homogeneity. The soluble PPO purification was achieved by hydrophobic interaction chromatography and gel filtration chromatography, with apparent molecular mass of 55 kDa. The membrane PPO purification was achieved by anion exchange chromatography and gel filtration with apparent molecular mass of 54 kDa. A totally denaturing SDS-PAGE indicated the presence of a single polypeptide with an apparent molecular mass of 60 kDa for both fractions, with the band also revealed by Western blot. A partially denaturing SDS-PAGE stained a single active 36 kDa band for both fractions. Under native isoelectric focusing, a major acidic band of pH 5.2 was detected in both fractions. Kinetic characterization of PPO on the natural substrate l-dopa was carried out.
Assuntos
Beta vulgaris/enzimologia , Catecol Oxidase/isolamento & purificação , Raízes de Plantas/enzimologia , Catecol Oxidase/química , Catecol Oxidase/metabolismo , Eletroforese em Gel de Poliacrilamida , Concentração de Íons de Hidrogênio , CinéticaRESUMO
The inhibition of mushroom tyrosinase by cucumber extracts was evaluated. The inhibitory effect was measured by both polarographic and spectrophotometric methods. The commercial aldehyde, trans,cis-2,6-nonadienal, described as a major volatile compound of cucumber, was characterized as a noncompetitive inhibitor against 4-tert-butylcatechol oxidation by mushroom tyrosinase. The K(I) obtained was 3.4 mM. Polyphenol oxidase (PPO) activity was not detected in cucumber skin extracts. However, the presence of PPO was revealed by Western blot; a single band was found with a M(r) of 53 kDa. These results support the assumption that the enzyme PPO is present in the cucumber skin, but its activity is inhibited. Peroxidase (PO) was also found in cucumber skin extracts. This enzyme was detected in the soluble fraction but not in the membrane fraction. The kinetic characterization of PO was carried out. Native isoelectric focusing revealed several acidic PO isoenzymes with a pI in the range between 5 and 6, a basic isoenzyme, and one principal neutral isoenzyme of pI = 7.2.