Anti-Influenza Triterpene Saponins from the Bark of Burkea africana

J Nat Prod. 2018 Mar 23;81(3):515-523. doi: 10.1021/acs.jnatprod.7b00774.

Christina E Mair ¹, Ulrike Grienke ¹, Anke Wilhelm ², Ernst Urban ³, Martin Zehl ¹ ³ ⁴, Michaela Schmidtke ⁵, Judith M Rollinger ¹

Affiliations

1 Department of Pharmacognosy, Faculty of Life Sciences , University of Vienna , Althanstraße 14 , 1090 Vienna , Austria.
2 Department of Chemistry , University of the Free State , PO Box 339, 9300 Bloemfontein , South Africa.
3 Department of Pharmaceutical Chemistry, Faculty of Life Sciences , University of Vienna , Althanstraße 14 , 1090 Vienna , Austria.
4 Department of Analytical Chemistry, Faculty of Chemistry , University of Vienna , Währinger Straße 38 , 1090 Vienna , Austria.
5 Institute of Medical Microbiology, Section Experimental Virology, Jena University Hospital , Hans-Knöll-Straße 2 , 07745 Jena , Germany.

PMID: 29394063 DOI: 10.1021/acs.jnatprod.7b00774

Abstract

In an in vitro cytopathic effect inhibition assay with the H3N2 Influenza Virus A/Hong Kong/68 (HK/68), the bark extract of Burkea africana was found to be a promising Antiviral lead with an IC₅₀ value of 5.5 μg/mL without noteworthy cytotoxicity in Madin Darby canine kidney cells. After several chromatographic steps, triterpene saponins of the lupane and oleanane types were identified as the bioactive principles. In total, eight new triterpene saponins (1-8) with four so far undescribed aglycone structures were isolated and characterized via HRESIMS, GC-MS, and 1D and 2D NMR spectroscopy. Their anti-influenza virus activity on HK/68 and the 2009 pandemic H1N1 strain A/Jena/8178/09 revealed the most potent effects by compounds 7 and 8, with IC₅₀ values between 0.05 and 0.27 μM. This is the first time triterpene saponins have been reported as constituents of the investigated plant material.

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