Phytochemical Analysis of a Cytotoxic Fraction of Quassia silvestris using LC-HR-ESI-MS n Michel Feussi Tala, a,b * Ferdinand Mouafo Talontsi, c Guang-Zhi Zeng, b Hippolyte Kamdem Wabo, a Michael Spiteller, c Ning-Hua Tan a * and Pierre Tane a ABSTRACT: Introduction – The genus Quassia is a promising source of secondary metabolites with biological potential including antimalarial and cytotoxic activities. Limited data are available on the phytochemistry and pharmacology of Quassia silvestris Cheek & Jongkind, a Cameroonian medicinal plant used to treat various ailments. Objectives – To carry out the bioassay-guided fractionation and LC-HR-ESI-MS analyses of the leaves extract from Q. silvestris; to purify the active fractions and isolate the major compounds using different chromatographic and spectroscopic methods. The obtained compounds will be evaluated for their biological activity. Material and methods – Following the cytotoxic screening and LC-HR-ESI-MS profiling of fractions obtained from partition of the methanolic extract of Q. silvestris leaves, the CH 2 Cl 2 -soluble fraction which exhibited the highest cytotoxicity was retained for further investigations. Results – Sixteen squalene-derived metabolites were identified with oxasqualenoid derivatives being the most predominant. Among the isolates, structure elucidation of two new oxasqualenoids quassiols E (1) and F (2), were achieved by NMR (one- dimensional (1D) and two-dimensional (2D)) and MS methods. The newly characterised compounds 1 and 2, together with the known tetraol (3) and 3-oxo-oleanoic acid (16) displayed moderate cytotoxicity. Conclusion – The identification and structural characterisation of highly oxidised squalene derived metabolites from this plant may provide important insight data for further pharmacological investigations. The LC-HR-ESI-MS n method reported here could be developed as a rapid and efficient tool for the analyses of structurally related compounds in the genera Quassia, Simarouba, and Eurycoma of the subfamily Simarouboideae. Copyright © 2016 John Wiley & Sons, Ltd. Supporting information can be found in the online version of this article. Keywords: Simaroubaceae; Quassia silvestris; oxasqualenoids; triterpenoids; high-resolution mass spectrometry; cytotoxicity Introduction The genus Quassia belongs to the Simaroubaceae family and com- prises about 40 species distributed throughout tropical countries (Thomas, 1990). This genus is represented in Cameroon by four species including Quassia silvestris Cheek & Jongkind formerly called Hannoa klaineana Pierre & Engl. (Cheek and Jongkind, 2008). Most of the Quassia plants are locally used in central Africa as medicinal remedies to treat malaria, fever, dyspepsia, diarrhoea, rheumatism, tumours, intestinal diseases, dysentery, diabetes, and constipation (Morton, 1981; François et al., 1998; Ajaiyeoba and Krebs, 2003; Alves et al., 2014). Previous chemical studies of some members of this genus reported flavonoids, alkaloids, coumarins, and triterpenoids including quassinoids and oxasqualenoids with interesting biological activities, such as cytotoxic, antitumor, antiulcer, anti-inflammatory, antimalarial, antibacterial, antifungal, antiviral, insecticidal, and herbicidal potentials (Miller et al., 1995; Ajaiyeoba and Krebs, 2003; Adesanwo et al., 2004; Alves et al., 2014). In continuation of our research programme for cytotoxic sec- ondary metabolites from Cameroonian medicinal plants (Tala et al., 2013, 2015), a bioassay-guided fractionation of the dichloro- methane (CH 2 Cl 2 ) extract from Q. silvestris leaves using three human cancer cell lines (A-549, BGC-823, and HeLa) and subsequent liquid chromatography high resolution electrospray ionisation multi-stage mass spectrometry (LC-HR-ESI-MS n ) analysis (Table 1) were carried out. From the LC-HR-ESI-MS profiling of the extract, 16 squalene-derived metabolites (1–16) were identified with oxasqualenoid derivatives being the most predominant (Fig. 1). Further purifications using different chromatographic methods provided sufficient amount for full structural characteri- sation of compounds 1–3 and 12–16. Their structures were elucidated on the basis of their NMR (one-dimensional (1D) and two-dimensional (2D)) and MS data (Table 1). To the best of our * Correspondence to: Michel F. Tala, Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstrasse 2, D-37077 Göttingen, Germany. Email: ftalamichel@gmail.com **Correspondence to: Ning-Hua Tan, State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, Yunnan, P.R. China. Email: nhtan@mail.kib.ac.cn a Department of Chemistry, University of Dschang, P.O. Box 67, Dschang, Cameroon b State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201Yunnan, P.R. China c Institute of Environmental Research (INFU) of the Faculty of Chemistry and Chemical Biology, TU Dortmund, Otto-Hahn-Str. 6, D-44221, Dortmund, Germany Phytochem. Anal. 2016 Copyright © 2016 John Wiley & Sons, Ltd. Research Article Received: 7 August 2016, Revised: 15 October 2016, Accepted: 24 October 2016 Published online in Wiley Online Library (wileyonlinelibrary.com) DOI 10.1002/pca.2663