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seco-iridoids from Calycophyllum spruceanum (Rubiaceae)
Luz Margarita Cardona Zuleta1, Alberto José Cavalheiro, Dulce Helena Siqueira Silva
1NuBBE-Núcleo de Bioensaios, Biossíntesse e Ecofisiologia de Produtos Naturais, Instituto de Química, Universidade Estadual Paulista, CP 355, CEP 14801-970, Araraquara, São Paulo, Brazil.
Abstract:
Three seco-iridoids 7-methoxydiderroside, 6'-O-acetyldiderroside and 8-O-tigloyldiderroside, were isolated from the wood bark of Calycophyllum spruceanum together with the known iridoids loganetin, loganin and the seco-iridoids secoxyloganin, kingiside and diderroside. Their structures were elucidated by means of NMR and MS spectral data analysis. Using NOE correlations and coupling constants, the relative stereochemistry of the new derivatives was established. 7-Methoxydiderroside, 6'-O-acetyldiderroside and the known secoxyloganin and diderroside showed in vitro activity against trypomastigote forms of Trypanosoma cruzi, with IC(50) values of 59.0, 90.2, 74,2 and 84.9 microg/mL, respectively and were compared to the standard gentian violet (IC(50) 7.5 microg/ml).