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In the pursuit of identifying the novel resin glycoside modulators glucose-6-phosphatase and α-glucosidase enzymes, associated with blood sugar regulation, methanol-soluble extracts from the flowers of Ipomoea murucoides (cazahuate, Nahuatl), renowned for its abundance of glycolipids, were employed. The methanol-soluble extracts were fractionated by applying the affinity-directed method with glucose-6-phosphatase enzymes from a rat's liver and α-glucosidase enzymes from its intestines. Mass spectrometry and nuclear magnetic resonance were employed to identify the high-affinity compound as a free ligand following the release from the enzymatic complex. Gel permeation through a spin size-exclusion column allowed the separated high-affinity molecules to bind to glucose-6-phosphatase and α-glucosidase enzymes in solution, which led to the identification of some previously reported resin glycosides in the flowers of cazahuate, where a glycolipid mainly structurally related to murucoidin XIV was observed. In vitro studies demonstrated the modulating properties of resin glycosides on the glucose-6-phosphatase enzyme. Dynamic light scattering revealed conformational variations induced by resin glycosides on α-glucosidase enzyme, causing them to become more compact, akin to observations with the positive control, acarbose. These findings suggest that resin glycosides may serve as a potential source for phytotherapeutic agents with antihyperglycemic properties.
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ETHNOPHARMACOLOGICAL RELEVANCE: Extracts of the aerial part of Phyllanthus amarus have been extensively used in several countries to cure diabetes. No data is available on the impact of gastrointestinal digestion of such crude extracts on their antidiabetic activity. AIM OF THE STUDY: The aim of this study was to identify active fractions and compounds of fresh aerial parts of P. amarus extracted by an infusion method that are responsible for antidiabetic effects occurring at the level of glucose homeostasis. MATERIALS AND METHODS: An aqueous extract was obtained by an infusion method and its polyphenolic composition was analysed by reverse phase UPLC-DAD-MS. The influence of in vitro gastrointestinal digestion was evaluated both on the chemical composition and on the antidiabetic effect of P. amarus infusion extract using glucose-6-phosphatase enzyme inhibition and stimulation of glucose uptake. RESULTS: Analysis of the chemical composition of the crude extract revealed the presence of polysaccharides and various families of polyphenols such as phenolic acids, tannins, flavonoids and lignans. After simulated digestion, the total content of polyphenols decreased by about 95%. Caffeoylglucaric acid derivates and lignans exhibited strong stimulation of glucose uptake similar to metformin with an increase of 35.62 ± 6.14% and 34.74 ± 5.33% respectively. Moreover, corilagin, geraniin, the enriched polysaccharides fraction and the bioaccessible fraction showed strong anti-hyperglycemic activity with about 39-62% of glucose-6-phosphatase inhibition. CONCLUSION: Caffeoylglucaric acid isomers, tannin acalyphidin M1 and lignan demethyleneniranthin were reported for the first time in the species. After in vitro gastroinstestinal digestion, the composition of the extract changed. The dialyzed fraction showed strong glucose-6-phosphatase inhibition.
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Diabetes Mellitus , Lignanas , Phyllanthus , Extratos Vegetais/farmacologia , Extratos Vegetais/química , Phyllanthus/química , Glucose-6-Fosfatase , Lignanas/farmacologia , Hipoglicemiantes/farmacologia , Polifenóis/farmacologia , Glucose , DigestãoRESUMO
Type 2 diabetes is a worldwide prevalent disease that is due to a progressive loss of adequate ß-cell insulin secretion, frequently against a background of insulin resistance. In Mexican traditional medicine, the therapeutic use of hypoglycemic plants to control the disease is a common practice among type 2 diabetic patients. In the present work, we examined the traditional use of the aerial parts of Eryngium longifolium and the rhizome of Alsophila firma, consumed by people use over the day (in fasting state) to control their blood glucose levels, therefore, we aimed to assess the acute hypoglycemic effect of both plants. First, basic phytochemical profiles of both plants were determined and, subsequently, acute toxicity tests were carried out. Then, in vivo hypoglycemic tests were performed in streptozotocin-nicotinamide (STZ-NA) induced hyperglycemic Wistar rats and finally the effect of the plants on three enzymes involved in glucose metabolism was assayed in vitro. Through HPLC-DAD chromatography, caffeic acid, chlorogenic acid, rosmarinic acid, isoflavones, and glycosylated flavonoids were identified in E. longifolium, while the possible presence of flavanones or dihydroflavonols was reported in A. firma. Both plants exhibited a statistically significant hypoglycemic effect, without a dose-dependent effect. Furthermore, they inhibited glucose 6-phosphatase and fructose 1,6-bisphosphatase in in vitro assays, which could be associated with the hypoglycemic effect in vivo. Thus, this study confirmed for the first time the traditional use of the aerial part of E. longifolium and the rhizome of A. firma as hypoglycemic agents in a hyperglycemic animal model. In addition, it was concluded that their ability to regulate hyperglycemia could involve the inhibition of hepatic glucose output, which mainly controls glucose levels in the fasting state.
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Glycogen storage diseases (GSD) encompass a group of rare inherited diseases due dysfunction of glycogen metabolism. Hypoglycemia is the most common primary manifestation of GSD, and disturbances in glucose metabolism can cause neurological damage. The aims of this study were to first investigate the metabolic, genetic, and neurological profiles of children with GSD, and to test the hypothesis whether GSD type I would have greater neurological impact than GSD type IX. A cross-sectional study was conducted with 12 children diagnosed with GSD [Types: Ia (n=5); 1, Ib (n=1); 4, IXa (n=5); and 1, IXb (n=1)]. Genetic testing was conducted for the following genes using multigene panel analysis. The biochemical data and magnetic resonance imaging of the brain presented by the patients were evaluated. The criteria of adequate metabolic control were adopted based on the European Study on Glycogen Storage Disease type I consensus. Pathogenic mutations were identified using multigene panel analyses. The mutations and clinical chronology were related to the disease course and neuroimaging findings. Adequate metabolic control was achieved in 67% of patients (GSD I, 43%; GSD IX, 100%). Fourteen different mutations were detected, and only two co-occurring mutations were observed across families (G6PC c.247C>T and c.1039C>T). Six previously unreported variants were identified (5 PHKA2; 1 PHKB). The proportion of GSD IX was higher in our cohort compared to other studies. Brain imaging abnormalities were more frequent among patients with GSD I, early-symptom onset, longer hospitalization, and inadequate metabolic control. The frequency of mutations was similar to that observed among the North American and European populations. None of the mutations observed in PHKA2 have been described previously. Therefore, current study reports six GSD variants previously unknown, and neurological consequences of GSD I. The principal neurological impact of GSD appeared to be related to inadequate metabolic control, especially hypoglycemia.
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Encéfalo/diagnóstico por imagem , Doença de Depósito de Glicogênio/diagnóstico por imagem , Pré-Escolar , Feminino , Doença de Depósito de Glicogênio/genética , Humanos , Lactente , Recém-Nascido , Imageamento por Ressonância Magnética , Masculino , MutaçãoRESUMO
Metabolic syndrome comprises a cluster of metabolic disorders related to the development of cardiovascular disease and type 2 diabetes mellitus. In latter years, plant secondary metabolites have become of special interest because of their potential role in preventing and managing metabolic syndrome. Sesquiterpene lactones constitute a large and diverse group of biologically active compounds widely distributed in several medicinal plants used for the treatment of metabolic disorders. The structural diversity and the broad spectrum of biological activities of these compounds drew significant interests in the pharmacological applications. This review describes selected sesquiterpene lactones that have been experimentally validated for their biological activities related to risk factors of metabolic syndrome, together with their mechanisms of action. The potential beneficial effects of sesquiterpene lactones discussed in this review demonstrate that these substances represent remarkable compounds with a diversity of molecular structure and high biological activity, providing new insights into the possible role in metabolic syndrome management.
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De novo hepatic glucose production or hepatic gluconeogenesis is the main contributor to hyperglycemia in the fasting state in patients with type 2 diabetes (T2D) owing to insulin resistance, which leads to at least twice as much glucose synthesis compared to healthy subjects. Therefore, control of this pathway is a promising target to avoid the chronic complications associated with elevated glucose levels. Patients with T2D in the rural communities of Mexico use medicinal plants prepared as infusions that are consumed over the day between meals, thus following this rationale (consumption of the infusions in the fasting state), one approach to understanding the possible mechanism of action of medicinal plants is to assess their capacity to inhibit hepatic glucose production. Furthermore, in several of these plants, the presence of phenolic acids able to block the enzyme glucose-6-phosphatase (G6Pase) is reported. In the present work, extracts of Ageratina petiolaris, Bromelia karatas, Equisetum myriochaetum, Rhizophora mangle, and Smilax moranensis, which are Mexican plants that have been traditionally used to treat T2D, were assayed to evaluate their possible hepatic glucose output (HGO) inhibitory activity with a pyruvate tolerance test in 18-h fasted STZ-NA Wistar rats after oral administration of the extracts. In addition, the in vitro effects of the extracts on the last HGO rate-limiting enzyme G6Pase was analyzed. Our results showed that four of these plants had an effect on hepatic glucose production in the in vivo or in vitro assays. A. petiolaris and R. mangle extracts decreased glucose output, preventing an increase in the blood glucose levels and sustaining this prevented increase after pyruvate administration. Moreover, both extracts inhibited the catalytic activity of the G6Pase complex. On the other hand, even though S. moranensis and B. karatas did not exhibit a significant in vivo effect, S. moranensis had the most potent inhibitory effect on this enzymatic system, while the E. myriochaetum extract only inhibited hepatic glucose production in the pyruvate tolerance test. Because of the traditional method in which diabetic patients use plants, hepatic glucose production inhibition seems to be a mechanism that partially explains the common hypoglycemic effect. However, further studies must be carried out to characterize other mechanisms whereby these plants can decrease HGO.
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Odor transduction in the cilia of olfactory sensory neurons involves several ATP-requiring enzymes. ATP is generated by glycolysis in the ciliary lumen, using glucose incorporated from surrounding mucus, and by oxidative phosphorylation in the dendrite. During prolonged stimulation, the cilia maintain ATP levels along their length, by unknown means. We used immunochemistry, RT-PCR, and immunoblotting to explore possible underlying mechanisms. We found the ATP-shuttles, adenylate and creatine kinases, capable of equilibrating ATP. We also investigated how glucose delivered by blood vessels in the olfactory mucosa reaches the mucus. We detected, in sustentacular and Bowman's gland cells, the crucial enzyme in glucose secretion glucose-6-phosphatase, implicating both cell types as putative glucose pathways. We propose a model accounting for both processes.
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Trifosfato de Adenosina/metabolismo , Cílios/metabolismo , Glucose-6-Fosfatase/metabolismo , Glucose/metabolismo , Neurônios Receptores Olfatórios/metabolismo , Adenilato Quinase/genética , Adenilato Quinase/metabolismo , Animais , Transporte Biológico , Membrana Celular/metabolismo , Membrana Celular/ultraestrutura , Cerebelo/citologia , Cerebelo/metabolismo , Cílios/ultraestrutura , Creatina Quinase Forma BB/genética , Creatina Quinase Forma BB/metabolismo , Expressão Gênica , Transportador de Glucose Tipo 1/genética , Transportador de Glucose Tipo 1/metabolismo , Glucose-6-Fosfatase/genética , Glicólise , Masculino , Microssomos/metabolismo , Microssomos/ultraestrutura , Neurônios Receptores Olfatórios/citologia , Fosforilação Oxidativa , Ratos , Ratos Sprague-Dawley , Técnicas de Cultura de TecidosRESUMO
We evaluated the effects of supplementation with oral l-glutamine in Walker-256 tumor-bearing rats. A total of 32 male Wistar rats aged 54 days were randomly divided into four groups: rats without Walker-256 tumor, that is, control rats (C group); control rats supplemented with l-glutamine (CG group); Walker-256 tumor rats without l-glutamine supplementation (WT group); and WT rats supplemented with l-glutamine (WTG group). l-Glutamine was incorporated into standard food at a proportion of 2 g/100 g (2%). After 10 days of the experimental period, the jejunum and duodenum were removed and processed. Protein expression levels of key enzymes of gluconeogenesis, that is, phosphoenolpyruvate carboxykinase and glucose-6-phosphatase, were analyzed by western blot and immunohistochemical techniques. In addition, plasma corticosterone, glucose, insulin, and urea levels were evaluated. The WTG group showed significantly increased plasma glucose and insulin levels ( p < 0.05); however, plasma corticosterone and urea remained unchanged. Moreover, the WTG group showed increased immunoreactive staining for jejunal phosphoenolpyruvate carboxykinase and increased expression of duodenal glucose-6-phosphatase. Furthermore, the WTG group presented with less intense cancer cachexia and slower tumor growth. These results could be attributed, at least partly, to increased intestinal gluconeogenesis and insulinemia, and better glycemia maintenance during fasting in Walker-256 tumor rats on a diet supplemented with l-glutamine.
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Caquexia/tratamento farmacológico , Suplementos Nutricionais , Duodeno/enzimologia , Glucose-6-Fosfatase/metabolismo , Glutamina/farmacologia , Jejuno/enzimologia , Fosfoenolpiruvato Carboxiquinase (ATP)/metabolismo , Animais , Glicemia/metabolismo , Carcinoma 256 de Walker , Corticosterona/sangue , Duodeno/metabolismo , Gluconeogênese , Insulina/sangue , Jejuno/metabolismo , Masculino , Modelos Animais , Ratos , Ratos Wistar , Ureia/sangueRESUMO
Coffee is the main source of chlorogenic acid in the human diet, and it contains several chlorogenic acid isomers, of which the 5-caffeoylquinic acid (5-CQA) is the predominant isomer. Because there are no available data about the action of chlorogenic acids from instant coffee on hepatic glucose-6-phosphatase (G-6-Pase) activity and blood glucose levels, these effects were investigated in rats. The changes on G-6-Pase activity and liver glucose output induced by 5-CQA were also investigated. Instant coffee extract with high chlorogenic acids content (37.8%) inhibited (p < 0.05) the G-6-Pase activity of the hepatocyte microsomal fraction in a dose-dependent way (up to 53), but IV administration of this extract did not change the glycaemia (p > 0.05). Similarly, 5-CQA (1 mM) reduced (p < 0.05) the activity of microsomal G-6-Pase by about 40%, but had no effect (p > 0.05) on glucose output arising from glycogenolysis in liver perfusion. It was concluded that instant coffee extract with high content of chlorogenic acids inhibited hepatic G-6-Pase in vitro, but failed to reduce the glycaemia probably because the coffee chlorogenic acids did not reach enough levels within the hepatocytes to inhibit the G-6-Pase and reduce the liver glucose output.
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Glicemia/metabolismo , Ácido Clorogênico/farmacologia , Café/química , Glucose-6-Fosfatase/antagonistas & inibidores , Microssomos Hepáticos/enzimologia , Extratos Vegetais/química , Ácido Quínico/análogos & derivados , Animais , Ácido Clorogênico/química , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Índice Glicêmico/efeitos dos fármacos , Humanos , Fígado/efeitos dos fármacos , Fígado/metabolismo , Masculino , Microssomos Hepáticos/efeitos dos fármacos , Ácido Quínico/química , Ácido Quínico/farmacologia , Ratos , Ratos WistarRESUMO
The objective of this study was to investigate the impact of elevated tissue omega-3 (n-3) polyunsaturated fatty acids (PUFA) status on age-related glucose intolerance utilizing the fat-1 transgenic mouse model, which can endogenously synthesize n-3 PUFA from omega-6 (n-6) PUFA. Fat-1 and wild-type mice, maintained on the same dietary regime of a 10% corn oil diet, were tested at two different ages (2 months old and 8 months old) for various glucose homeostasis parameters and related gene expression. The older wild-type mice exhibited significantly increased levels of blood insulin, fasting blood glucose, liver triglycerides, and glucose intolerance, compared to the younger mice, indicating an age-related impairment of glucose homeostasis. In contrast, these age-related changes in glucose metabolism were largely prevented in the older fat-1 mice. Compared to the older wild-type mice, the older fat-1 mice also displayed a lower capacity for gluconeogenesis, as measured by pyruvate tolerance testing (PTT) and hepatic gene expression of phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6 phosphatase (G6Pase). Furthermore, the older fat-1 mice showed a significant decrease in body weight, epididymal fat mass, inflammatory activity (NFκ-B and p-IκB expression), and hepatic lipogenesis (acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) expression), as well as increased peroxisomal activity (70-kDa peroxisomal membrane protein (PMP70) and acyl-CoA oxidase1 (ACOX1) expression). Altogether, the older fat-1 mice exhibit improved glucose homeostasis in comparison to the older wild-type mice. These findings support the beneficial effects of elevated tissue n-3 fatty acid status in the prevention and treatment of age-related chronic metabolic diseases.
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Proteínas de Caenorhabditis elegans/metabolismo , Ácidos Graxos Dessaturases/metabolismo , Ácidos Graxos Ômega-3/metabolismo , Intolerância à Glucose/metabolismo , Acetil-CoA Carboxilase/genética , Acetil-CoA Carboxilase/metabolismo , Fatores Etários , Animais , Glicemia/metabolismo , Proteínas de Caenorhabditis elegans/genética , Ácidos Graxos Dessaturases/genética , Ácido Graxo Sintases/genética , Ácido Graxo Sintases/metabolismo , Expressão Gênica , Gluconeogênese/genética , Glucose/metabolismo , Intolerância à Glucose/genética , Glucose-6-Fosfatase/genética , Glucose-6-Fosfatase/metabolismo , Homeostase/genética , Immunoblotting , Insulina/sangue , Lipogênese/genética , Fígado/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Fosfoenolpiruvato Carboxiquinase (ATP)/genética , Fosfoenolpiruvato Carboxiquinase (ATP)/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
La enfermedad de von Gierke, también conocida como enfermedad de deposito de glucógeno tipo Ia, es una enfermedad producida por la deficiencia de la unidad catalítica de la G6Pasa-a, encargada de hidrolizar la glucosa 6 fosfato en el citoplasma celular durante la gluconeogénesis y la glucogenolisis. Las complicaciones a largo plazo son hipoglicemia severa y alteraciones en el crecimiento. En los niños más pequeños la enfermedad típicamente se presenta con crisis convulsivas y hepatomegalia que se manifiestan a los 6 y 8 meses. Otras complicaciones son osteoporosis, gota, enfermedad renal, hipertensión pulmonar y adenomas hepáticos que pueden malignizarse. No se ha encontrado una cura y de no recibir un manejo adecuado es letal en las primeras dos décadas de la vida. El tratamiento consiste en terapia nutricional, asociada a varios medicamentos convencionales. Algunos pacientes pueden requerir transplante renal o transplante hepático. Una nueva esperanza se ha abierto con el advenimiento de la terapia génica con vectores virales, esta estrategia hasta ahora esta siendo desarrollada, pero los estudios realizados han mostrado una luz de esperanza para investigadores, médicos y pacientes. Faltan estudios para que estos tratamientos permitan un beneficio a largo plazo y su aplicación en humanos, ya que las pruebas como es de esperarse solo han sido desarrolladas en modelos animales.
Von Gierke disease, also known as glycogen storage disease type Ia, is a disease caused by deficiency of the G6Pase-a catalytic unit, which hydrolyzes glucose-6- phosphate in the cell cytoplasm during gluconeogenesis and glycogenolysis. Long term complications include severe hypoglycemia and growth disturbances. In small children, the disease typically presents with seizure crisis and hepatomegaly which become manifest at the age of 6 and 8 months. Other complications include osteoporosis, gout, renal disease, pulmonary hypertension and hepatic adenomas which can become malignant. No cure has been found for this disease and it can turn out to be lethal if no appropriate management is given during the first two decades of life. The treatment consists of nutritional therapy associated with a number of conventional drugs. Some patients may require renal or liver transplant. A new hope has emerged with the arrival of gene therapy with viral vectors, strategy that is being developed hitherto, yet performed studies have shown a glimmer of hope for investigators, doctors and patients. There is a need for studies so these treatments allow for a longer term benefit and their application in humans since, as expected, the tests have been developed only in animal models.
A doença de Von Gierke, também conhecida como Glicogenose tipo I, é uma doença produzida pela deficiência da unidade catalítica da G6Pasa-a, encarregada de hidrolisar a glicose 6 fosfato no citoplasma celular durante a gliconeogênese e a glicogenólise. As complicações a longo prazo são hipoglicemia severa e alterações no crescimento. Nas crianças menores a doença se apresenta tipicamente com crises convulsivas e hepatomegalia que se manifestam aos 6 e 8 meses. Outras complicações são osteoporose, gota, doença renal, hipertensão pulmonar e adenomas hepáticos que podem malignizar-se. Não foi encontrada uma cura e se não recebe tratamento adequado é letal nas primeiras duas décadas de vida. O tratamento consiste em terapia nutricional, associada a vários medicamentos convencionais. Alguns pacientes podem requerer transplante renal ou transplante hepático. Uma nova esperança apareceu com a terapia gênica com vetores virais, esta estratégia até agora esta sendo desenvolvida, mas os estudos realizados mostram uma luz de esperança para pesquisadores, médicos e pacientes. Faltam estudos para que estes tratamentos permitam um beneficio a longo prazo e a sua aplicação em humanos, já que os testes como é de se esperar só foram desenvolvidos em modelos animais.
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Humanos , Criança , Doença de Depósito de Glicogênio Tipo I , Terapia Genética , Carcinoma Hepatocelular , GlicogênioRESUMO
From the cholroform extract of the aerial parts of Couepia paraensis the triterpenes beta-sitosterol1, betulinic acid acetate 2, and oleanolic acid acetate 3, were isolated. Six triterpenes from the chloroform-methanol, acids: oleanolic 4, pomolic 5, ursolic 6, betulinic 7, 6-beta-hydroxybetulínic 8. Additionally from the methanolic extract three flavonoids were isolated: mricetin 9, quercetin 10 y rutina 11. The chloroform and chloroform-methanol extracts were not citotoxic at concentration of 2,5 and 3,1 ug/ml respectively after 24 hours of incubation. The methanol extract was found to be harmless to a concentration of 50 ug/ml, both at 24 hours (LD50 = 10.77 ug/ml) and 120 hours (LD50 = 28.86 ug/ml) of incubation. Only the methanol extract showed significant inhibition (41 percent) of the activity of G-6-Pase in intact microsomes without affecting the activity of the enzyme in microsomes broken.
Se aislaron e identificaron tres triterpenos: beta-sitosterol 1, acetato del ácido betulínico, 2 y acetato del ácido oleanólico 3 del extracto clorofórmico. Seis triterpenos del extracto cloroformo: metanol (9:1) que fueron identificados como ácidos: oleanólico 4, pomólico 5, ursólico 6, betulínico 7, 6-beta-hidroxibetulínico 8. Mientras que del extracto metanólico se identificaron 3 flavoniodes: miricetina 9, quercetina 10 y rutina 11. Los extractos de cloroformo y cloroformo /metanol resultaron inocuos hasta las concentraciones de 2,5 y 3,1ug/ml respectivamente, después de 24 horas de incubación. El extracto metanólico es inocuo hasta una concentración de 50 ug/ml, tanto a 24 horas (LD50 = 10,77 ug/ml) como a 120 horas (LD50 = 28,86 ug/ml) de incubación. Solamente el extracto metanólico mostró una inhibición significativa (41 por ciento) de la actividad de la G-6-Pasa de microsomas intactos sin afectar la actividad de la enzima en microsomas rotos.
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Citotoxinas , Chrysobalanaceae/química , Flavonoides/análise , /antagonistas & inibidores , Triterpenos/análise , Fatores de TempoRESUMO
Os extratos aquoso e etanólico derivados de doze espécies coletadas na Amazônia venezuelana foram testados quanto à atividade antioxidante utilizando um radical DPPH e o efeito inibitório sobre a hidrólise de glicose-6-fosfato nos microssomas intactos e perturbados. Sem exceção, todos os extratos inibiram, em maior ou menor grau, a atividade enzimática microssomal de G-6-Pase, resultando em maior inibição nos microssomas intactos do que nos perturbados. Efeitos marcantes foram observados para os extratos aquoso e etanólico de: Tontelea ovalifolia, Gustavia pulchra, Phthirusa verruculosa, Phthirusa castillana, Psittacanthus acimarius, Tetrapterys styloptyera e Vismia japurensis. Os extratos etanólicos foram seqüestradores do radical DPPH mais eficazes do que os correspondentes extratos aquosos em todos os casos. O extrato etanólico de Endlicheria anomala e o extrato aquoso de Phthirusa verruculosa exibiram as melhores CI50 com 100 e 250.0 ppm, respectivamente. Os valores de Kobs calculados para os extratos alcoólicos foram mais baixos do que os dos extratos aquosos das mesmas espécies, exceto Psittacanthus acimarius. Estes resultados poderiam estar relacionados a diferentes concentrações, ou mais provavelmente a diferentes composições de princípios ativos em ambos extratos.
The aqueous and ethanol extracts derived from twelve plant species collected in the Venezuelan Amazon have been tested for antioxidant activity using a DPPH radical and inhibitory effect on the hydrolysis of glucose-6-phosphate in intact and disrupted microsomes. Without exception, all the extracts inhibited, to a greater or lesser degree, microsomal G-6-Pase enzymatic activity, resulting in greater inhibition on intact microsomes than on disrupted ones. Marked effects were observed for aqueous and ethanol extracts of: Tontelea ovalifolia, Gustavia pulchra, Phthirusa verruculosa, Phthirusa castillana, Psittacanthus acimarius, Tetrapterys styloptyera and Vismia japurensis. Ethanol extracts were more effective DPPH radical scavengers than the corresponding aqueous extracts in all the cases. The ethanol extract of Endlicheria anomala and the aqueous extract of Phthirusa verruculosa, showed the best IC50 with 100 and 250.0 ppm, respectively. The Kobs calculated for the alcoholic extracts were lower than those of the aqueous extracts for the same species, except Psittacanthus acimarius. These results could be related to different concentrations, or more likely different compositions of active principles in both extracts.