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The treatment of neurological disorders and neurodegenerative diseases is related to the levels of acetylcholine (ACh) through the inhibition of acetylcholinesterase (AChE). Galanthamine, an important alkaloid isolated from the Amaryllidaceae family, is approved for the pharmacological treatment of Alzheimer's disease (AD) and acts by inhibiting the acetylcholinesterase (AChE) activity. In the present study, Ellman's method was used to verify the inhibition of AChE activity of some isoquinolines alkaloids such as galanthamine, montanine, hippeastrine and pretazettine. At the concentrations 1mM, 500 microm and 100 microm, galanthamine presented an AChE inhibition higher than 90%. Montanine inhibited, in a dose-dependent manner, more than 50% of the enzyme at 1mM concentration. With the concentrations 500 microm and 100 microm, 30-45% of AChE activity inhibition was detected. The alkaloids hippeastrine and pretazettine presented no significant inhibition of the AChE activity. The results demonstrate that montanine significantly inhibits AChE activity at the tested concentrations, suggesting the necessity of further investigations on this alkaloid use in treating neurological disorders.

Recebido em 20/12/07; aceito em 4/6/08; publicado na web em 5/11/08 ANTIOXIDANT AND ANTICOLINESTERASIC EFFECTS OF Hippeastrum SPECIES (AMARYLLIDACEAE). Amaryllidaceae family is an important source of bioactive molecules and considering the taxonomic relationships, it is relevant to investigate the genus Hippeastrum. Thus, the aim of this work was to determine antioxidant and anticholinesterasic activities of Hippeastrum morelianum, Hippeastrum psittacinum and Hippeastrum santacatarina. Both antioxidant and acetylcholinesterasic activities of extracts were determinated by bioautography as 10 mg/mL and 0.1 mg/mL, respectively. The antioxidant activity of alkaloid lycorine, determinated spectrophotometrically with DPPH, indicated an IC 50 value of 0.326 mM.Keywords: Amaryllidaceae; antioxidant; anticholinesterasic. IntrodUçãoA etiologia da Doença de Alzheimer (DA) permanece desconhecida, mas estudos post mortem têm mostrado que a doença é caracterizada pela diminuição da função colinérgica no cérebro.1 Os mais modernos medicamentos utilizados para tratar os sintomas da DA elevam os níveis de acetilcolina pela inibição da enzima acetilcolinesterase (AChE). Ensaios desenvolvidos para detectar esta atividade estão sendo amplamente utilizados para avaliar um grande número de plantas utilizadas popularmente para melhorar a memória. Sabe-se também que o dano causado por espécies reativas de oxigênio, atualmente, é considerado um fator contribuinte de diversas doenças, incluindo a DA.3 Assim, identificar o potencial antioxidante de uma substância pode credenciá-la a ser uma molécula bioativa mais completa quando se considera o conjunto de suas propriedades. Dessa forma, é adequada a associação de ambos os ensaios para um estudo bioguiado mais eficiente.Na busca por novos fármacos, os produtos naturais destacam-se pela diversidade estrutural e, assim, as plantas são candidatas importantes para screening de novos compostos bioativos. Ao considerar as informações botânicas e quimio-taxonômicas, a eleição das plantas a serem investigadas torna-se mais selecionada. Considerando esse conjunto de fatores, a família Amaryllidaceae, particularmente, desponta como uma fonte promissora de novas substâncias bioativas, justificando a avaliação dos gêneros presentes no Brasil.O alcalóide galantamina foi, inicialmente, isolado de Galanthus woronowii, mas atualmente é obtido a partir de Narcissus sp. e Leucojum aestivum, assim como sinteticamente. A partir da descoberta deste alcalóide enquanto potente inibidor da enzima AChE, sua aprovação pelo FDA (Food and Drug Administration) em 2001 para comercialização e, conseqüentemente, importante utilização na DA, o interesse no estudo químico e farmacológico da família Amaryllidaceae vem aumentando exponencialmente. 4,5 Um screening do extrato bruto e das frações enriquecidas em alcalóides obtidas durante a extração ácido-base auxilia no direcionamento das investigações de isolamento e elucidação estrutural dessas substâncias, bem como contribui para a triagem de gêneros e espécies promissoras...

Many works have reported the interaction between selenium and mercury in the mammalian body and that chalcogen seems to have a protective effect against mercury toxicity. The aim of this study was to investigate the hemolytic effects of sodium selenite and/or mercuric chloride in human blood under in vitro conditions. For this, total venous blood from healthy subjects (males and females) was heparinized and incubated at 37 degrees C for 90 min with different concentrations of sodium selenite and/or mercuric chloride. The hemolytic effects of compounds were evaluated by measuring plasma hemoglobin concentration after centrifugation. In addition, 2-thiobarbituric acid reactive substances (TBARS) from plasma and erythrocytes, as well as erythrocyte nonprotein thiols (NPSH), were also evaluated in order to investigate molecular mechanisms related to selenite- or mercury-induced hemolysis. Mercuric chloride and sodium selenite, alone (400 microM), promoted a small in vitro hemolytic effect in human erythrocytes. However, when blood was exposed to both compounds (200 microM of each), there was an extremely high synergistic hemolytic effect. The exposure of blood to sodium selenite (400 microM), mercuric chloride (400 microM), and both compounds (200 microM each) did not alter erythrocyte TBARS levels. Sodium selenite presented a high oxidant effect toward erythrocyte NPSH; however, this effect was inhibited by mercuric chloride. The current results point to a synergistic hemolytic effect of sodium selenite and mercuric chloride in human blood, suggesting new understanding on the selenium-mercury antagonism. Moreover, this observed hemolysis seems to be not related to lipoperoxidation or thiol depletion.