Abstract
Through bioassay-guided fractionation, 13 compounds (1–13) were isolated from the CH2Cl2/MeOH (1:1) extracts of the root bark of Newbouldia leavis and characterized mainly by NMR and X-ray spectroscopy. Among these, nine quinone derivatives (1–7, 12–13), one triterpeniod (8), and three steroids (9–11) were isolated. The stereochemistry of 3-hydroxy furonaphthoquinones isolated from this plant has been established for the first time as (2S,3R) on the basis of single X-ray crystal structure analysis and show marked 3 J H,H deviations from the Karplus curve from 1H-NMR spectral analysis. The fractions together with three of the isolated compounds namely lapachol, 2-acetyl-naphtho [2,3-b]furan-4,9-dione, and 2-(1-hydroxyethyl)-2-acetyl-naphtho[2,3-b]furan-4,9-dione were screened against Onchocerca ochengi parasites. Lapachol and 2-(1-hydroxyethyl)-2-acetyl-naphtho[2,3-b]furan-4,9-dione showed 100 % inhibition at a concentration of 5 μg/mL after 5 days.
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Acknowledgments
This work was supported by a grant from the TWAS-UNESCO Associateship scheme to Dr. Eyong K, IIT Madras India for facilities and Pr. Cho Ngwa for Bioassys.
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Eyong, K.O., Ketsemen, H.L., Ghansenyuy, S.Y. et al. Chemical constituents, the stereochemistry of 3-hydroxy furonaphthoquinones from the root bark of Newbouldia laevis Seem (Bignoniaceae), and screening against Onchocerca ochengi parasites. Med Chem Res 24, 965–969 (2015). https://doi.org/10.1007/s00044-014-1173-z
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DOI: https://doi.org/10.1007/s00044-014-1173-z