| Summary: | This work describes the isolation and structural elucidation of some chemical constituents as well as antioxidant, anticholinesterasic and skin anti-inflammatory activities of extracts and some of the isolated compounds from Coutarea hexandra (Jacq.) K. Schum. (Rubiaceae). In the antioxidant assays, extracts from roots and leaves, when compared to positive controls used, free scavenger radical and inhibited the formation of peroxide of the linoleic acid. In the anticholinesterase and anti-inflammatory assays, at 0.6 mg/ear, some extracts from roots were effective in inhibiting the effects of the anticholinesterase enzyme and the formation of ear edema. The phytochemical investigation of some active extracts from roots resulted in the isolation of three phytosteroids (sitosterol, stigmasterol and sitostenone), a
diterpene (2β,3α-dihydroxy-11-oxo-ros-5-ene), two triterpenes (2β,3α-dihydroxy-11,16-dioxo-
5-ene-octanor-cucurbitacin and 23,24-diidrocucurbitacin F 25-acetate) and five 4-phenylcoumarin derivatives [5,7,8-trimethoxy-4-(3,4-dihydroxyphenyl)coumarin, 5-hydroxy-7-methoxy-4-(p-hydroxyphenyl)-coumarin, 5,7,8-trimethoxy-4-(p-methoxyphenyl)coumarin, 5,7-dimethoxy-4-(3-hydroxy-4-methoxyphenyl)coumarin,and 5,7-dimethoxy-4-(p-methoxyphenyl) coumarin]. These compounds had their structures elucidated based on their NMR spectral data and by comparison with literature data. Among isolated compounds, 2β,3α-dihydroxy-11,16-dioxo-5-ene-octanorcucurbitacin and 2β,3α-dihydroxy-11-oxo-ros-5-ene are being reported for the first time; 5-hydroxy-7-methoxy-4-(p-hydroxyphenyl)coumarin are being described for the first time as natural product and 5,7,8-trimethoxy-4-(3,4-dihydroxy-phenyl)coumarin occur for the first time in the Coutarea genus. In the anti-inflammatory assays, 5,7-dimethoxy-4-(pmethoxyphenyl) coumarin, 5-hydroxy-7-methoxy-4-(p-hydroxyphenyl) coumarin, 5,7-dimethoxy-4-(3-hydroxy-4-methoxy-phenyl)coumarin and 23,24-dihydro-cucurbitacin F 25-acetate, at 0.6 mg/ear, inhibited the edema by 35, 67, 19 and 30%, respectively. In the DPPH assays, 5-hydroxy-7-methoxy-4-(p-hydroxyphenyl)coumarin (43.70 0.21 μg/mL) and 5,7,8-trimethoxy-
4-(3,4-dihydroxyphenyl)coumarin (20.85 0.53 μg/mL) free scavenger radical with IC50 values
comparable to ascorbic acid and gallic acid, respectively. In the anticholinesterase assays, 2β,3α-dihydroxy-11-oxo-ros-5-ene showed inhibition of this enzyme. === Coordenação de Aperfeiçoamento de Pessoal de Nível Superior === O presente trabalho descreve o isolamento e a elucidação estrutural de alguns constituintes químicos, bem como das atividades antioxidante, anticolinesterásica e antiinflamatória cutânea de extratos das raízes, folhas e cascas do caule de Coutarea hexandra (Jacq.) K. Schum. (Rubiaceae), bem como de algumas das substâncias isoladas. Nos ensaios para avaliar atividade antioxidante, extratos das raízes e folhas forneceram os melhores resultados e alguns dos extratos das raízes foram eficazes em inibir o efeito da enzima acetilcolinesterase e a formação do edema de orelha induzido pelo óleo de cróton, na
concentração de 0,6 mg/orelha. A investigação fitoquímica efetuada com extratos das raízes resultou na obtenção de três fitoesteróides (sitosterol, estigmasterol e sitostenona), dois triterpenos (2β,3α-dihidroxi-11,16-dioxo-5-eno-octanorcucurbitacina e 25-acetato da 23,24-diidrocucurbitacina F), um diterpeno (2β,3α-diidroxi-11-oxo-ros-5-eno) e cinco derivados 4-fenilcumarínicos [5-hidroxi-7-metoxi-4-(p-hidroxifenil)cumarina, 5,7,8-trimetoxi-4-(pmetoxifenil) cumarina, 5,7-dimetoxi-4-(3-hidroxi-4-metoxifenil)cumarina, 5,7-dimetoxi-4-(pmetoxifenil) cumarina e 5,7,8-trimetoxi-4-(3,4-dihidroxifenil) cumarina]. Estes compostos tiveram suas estruturas elucidadas com base na análise dos dados de RMN e pela comparação com dados da literatura. Dentre as substâncias isoladas, o triterpeno 2β,3α-diidroxi-11,16-dioxo-5-eno-octanorcucurbitacina e o diterpeno 2β,3α-diidroxi-11-oxo-ros-5-eno estão sendo relatados pela primeira vez; a 5-hidroxi-7-metoxi-4-(p-hidroxifenil)cumarina está sendo descrita pela primeira vez como produto natural e a 5,7,8-trimetoxi-4-(3,4-diidroxifenil) cumarina ocorre pela primeira vez no gênero Coutarea. Nos ensaios antiinflamatórios, as substâncias 5,7-dimetoxi-4-(p-metoxifenil)cumarina, 5-hidroxi-7-metoxi-4-(p-hidroxifenil)cumarina e 25-acetato de 23,24-diidrocucurbitacina F inibiram o edema por cerca de 35, 67 e 30%, respectivamente. Nos ensaios frente ao DPPH, tanto a 5-hidroxi-7-metoxi-4-(p-hidroxifenil)cumarina (43,70 0,21 μg/mL) quanto a 5,7,8-trimetoxi-4-(3,4-diidroxifenil)cumarina (20,85 0,53 μg/mL) seqüestraram radicais livres com valores de CI50 comparáveis aos do ácido ascórbico e do ácido gálico, respectivamente. Nos ensaios
anticolinesterásicos, o diterpeno 2β,3α-diidroxi-11-oxo-ros-5-eno inibiu a ação da enzima acetilcolinesterase.
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