Anti-inflammatory effects of Terminalia phanerophlebia (Combretaceae) and identification of the active constituent principles

Abstract

The ‘Lebombo cluster leaf’ Terminalia phanerophlebia (Combretaceae) is used in traditional medicine in South Africa for a host of ailments, including aches and pain, wounds and infections, gynaecological conditions, inflammation, mental illness such as epilepsy, and sexually-transmitted diseases. Based on the anti-inflammatory activity (92.4% inhibition of the cyclooxygenase enzyme COX-2) initially observed for a crude extract, stems of T. phanerophlebia were here examined for the underlying phytochemical principles. Three cholestane triterpenoids β-sitosterol, β-sitostenone and stigmast-4-ene-3,6-dione were isolated from the ethanol extract by silica gel column chromatography via gradient elution with hexane/ethyl acetate mixtures. Structure elucidation was facilitated by use of physical and spectroscopic methods, including high field 2D NMR and mass spectroscopic techniques. The crude extract as well as β-sitosterol was seen to be selective inhibitors of the cyclooxygenase enzyme COX-2. This work is of chemosystematic relevance as it represents the first isolation of β-sitostenone and stigmast-4-ene-3,6-dione from any species of Terminalia.