Three phragmalin-type limonoids orthoesters and the structure of odoratone isolated from the bark of Entandrophragma candollei (Meliaceae)

Gervais Mouthé Happi; Guy Paulin Mouthe Kemayou; Hans-Georg Stammler; Beate Neumann; Mohamed Ismail; Simeon Fogue Kouam; Jean Duplex Wansi; Jean Claude Tchouankeu; Marcel Frese; Bruno Ndjakou Lenta; Norbert Sewald

doi:10.1016/j.phytochem.2020.112537

Three phragmalin-type limonoids orthoesters and the structure of odoratone isolated from the bark of Entandrophragma candollei (Meliaceae)

Phytochemistry. 2021 Jan:181:112537. doi: 10.1016/j.phytochem.2020.112537. Epub 2020 Oct 21.

Affiliations

¹ Department of Chemistry, Higher Teacher Training College, University of Bamenda, P.O Box 39, Bambili, Cameroon; Organic and Bioorganic Chemistry, Faculty of Chemistry, Bielefeld University, D-33501, Bielefeld, Germany; Department of Chemistry, Higher Teacher Training College, University of Yaounde I, P. O. Box 47, Yaounde, Cameroon. Electronic address: gervais20022003@yahoo.fr.
² Department of Chemistry, Higher Teacher Training College, University of Yaounde I, P. O. Box 47, Yaounde, Cameroon.
³ Inorganic and Structural Chemistry, Department of Chemistry, Bielefeld University, D-33501, Bielefeld, Germany.
⁴ Organic and Bioorganic Chemistry, Faculty of Chemistry, Bielefeld University, D-33501, Bielefeld, Germany; Department of Microbiology, Faculty of Science, Helwan University, Ain Helwan, 11795, Cairo, Egypt.
⁵ Department of Chemistry, University of Douala, Faculty of Sciences, 24157, Douala, Cameroon.
⁶ Department of Organic Chemistry, Faculty of Sciences, University of Yaounde I, 812, Yaounde, Cameroon.
⁷ Organic and Bioorganic Chemistry, Faculty of Chemistry, Bielefeld University, D-33501, Bielefeld, Germany.

PMID: 33099226
DOI: 10.1016/j.phytochem.2020.112537

Abstract

The phytochemical exploration of the Entandrophragma candollei stem bark extract led to the isolation and identification of twenty compounds including three undescribed phragmalin-class limonoids named encandollens C-E (1-3), the undescribed protolimonoid 5 together with sixteen known compounds. The structures of all the isolated compounds were determined by interpretation of their spectroscopic and spectrometric data including HRMS, 1D and 2D NMR analyses. The assignment of the absolute and relative stereochemistry of the undescribed compounds was achieved using SC-XRD analyses as well as NOESY experiments. The previously reported structure of odoratone (5a) was corrected as 23 R,24 S-dihydroxy-22 S,25-epoxytirucall-7-en-3-one (5) based on its NMR and SC-XRD data. Prieurianin (4) exhibited high cytotoxic activity on KB3-1 cell lines with an IC₅₀ of 1.47 μM compared to the reference griseofulvin (IC₅₀ = 17-21 μM). The results of the in silico docking of compound 4 supported and delivered further insights on its cytotoxicity.

Keywords: Cytotoxicity; Encandollens C-E; Entandrophragma candollei; In silico docking; Meliaceae; Phragmalin-class limonoid.

MeSH terms

Limonins* / pharmacology
Meliaceae*
Molecular Structure
Plant Bark

Substances

Limonins
phragmalin