Abstract
From the methanol extract of the stem bark of the African tree Antiaris africana Engler, two new bioactive metabolites were isolated, namely, the α-amyrin derivative 1β,11α-dihydroxy-3β-cinnamoyl-α-amyrin (antiarol cinnamate, 1) and a cardiac glycoside, 3β-O-(α-L-rhamnopyranosyl)-14β-hydroperoxy-5β-hydroxy-19-oxo-17β-card-20(22)-enolide (africanoside, 2a), together with the known compounds β-amyrin and its acetate, β-sitosterol and its 3-O-β-D-glucopyranoside, friedelin, ursolic and oleanolic acid, 19-norperiplogenin, strophanthidol,
strophanthidinic acid, periplogenin (3a), 3-epiperiplogenin, strophanthidin (3b) and 3,3′-dimethoxy-4′-O-β-D-xylopyronosyl-ellagic acid. Their structures were established on the basis of their
spectroscopic data and by chemical methods, while 3a was additionally confirmed by X‐ray crystal structure analysis. The aglycone moiety
possessing a hydroperoxy group was found for the first time in cardenolides. Compounds
1 and 2a showed no activity against bacteria, fungi, and microalgae; however, the crude extract
exhibited a high toxicity against Artemia salina and a selective antitumor activity against human tumor cell lines. Africanoside (2a) effected a concentration-dependent inhibition of tumor cell growth with a mean IC50 value of 5.3 nM.
Key words
Antiaris africana
- Moraceae - antiarol cinnamate - africanoside - sterol hydroperoxide - periplogenin
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Prof. Dr. Hartmut Laatsch
Institute for Organic and Biomolecular Chemistry
Georg-August-University Göttingen
Tammannstrasse 2
37077 Göttingen
Germany
Phone: + 49 5 51 39 32 11
Fax: + 49 5 51 39 96 60
Email: hlaatsc@gwdg.de
