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An Unprecedented Neolignan Skeleton from Chimarrhis turbinata

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journal contribution
posted on 25.03.2011, 00:00 by Carmen L. Cardoso, Ian Castro-Gamboa, Giovana M. Bergamini, Alberto J. Cavalheiro, Dulce H. S. Silva, Marcia N. Lopes, Angela R. Araújo, Maysa Furlan, Hugo Verli, Vanderlan da S. Bolzani
A lignan with a new skeleton named chimarrhinin (1) was isolated from an extract of the leaves of Chimarrhis turbinata, a Rubiaceae plant species. 13C NMR spectrometric techniques including 1D and 2D experiments and HRESIMS provided unequivocal structural confirmation of this new C6.C3 skeleton type. The relative configuration of 1 was established by 2D 1H−H analysis and J couplings, while its conformation was evaluated through molecular modeling using the RM1 semiempirical method, with the aid of coupling constants obtained by NMR analysis. The antioxidant activity of the new derivative 1 and two known and previously isolated phenolic derivatives (2 and 3) was investigated. An IC50 value of 7.50 ± 0.5 μmol L−1 was obtained for the new derivative 1, while 2 and 3 showed IC50 values of 18.60 ± 0.4 and 18.50 ± 0.6 μmol, respectively.