Abstract
Plants are an invaluable source of medicinal compounds and their use for healing is rooted in ancient times. Aptosimum procumbens (Scrophulariaceae) and Garuleum bipinnatum (Asteraceae) are two indigenous South African plants that have been used as traditional remedies. Phytochemical investigations were performed with the aim of isolating and identifying compounds that may be responsible for the recorded medicinal properties of these plants.
Various chromatographic techniques were utilized for the separation of the plant extract constituents. Several terpenoid compounds were isolated from both plants and the flavanone was isolated from A. procumbens. Nuclear magnetic resonance spectroscopy including 1H NMR, 13C NMR, COSY, DEPT, HMQC, HSCQ, HMBC and NOESY experiments were performed to allow for structure determination, the results of which will be discussed.
The iridoid glycosides angeloside, shanzhiside methyl ester, barlerin, a new compound foliamethoylshanzhiside methyl ester and the flavanone pinocembrin neohesperidoside were identified as constituents of A. procumbens. Fractionation of the G. bipinnatum extract afforded several sandaracopimar-15-ene diterpenoid derivatives, namely sandaracopimar-15-ene-8ƒÒ-ol, sandaracopimar-15-ene-8ƒÒ,11ƒÑ-diol, 12-O-acetylsandaracopimar-15-ene-8ƒÒ,11ƒÑ,12ƒÒƒn-triol, 11-O-acetylsandara-copimar-15-ene-8ƒÒ,11ƒÑ,12ƒÒƒn-triol, 11-O- feruoylsandaracopimar-15-ene-8ƒÒ,11ƒÑƒz12ƒÒ-triol and 11-O-p-coumaroylsandaracopimar-15-ene-8,11ƒÑ,12ƒÒ-triol.
Diterpenoids are known to possess antimicrobial properties enabling them to fight off various infections and monoterpenoid iridoid glycosides generally have anti-inflammatory properties that make them wound-healing agents. Flavonoids are a diverse group of compounds with enormous structural variations and have a wide range of medicinal properties. A general review on the structural classification, biosynthesis and biological activity of these secondary metabolites is given in this dissertation.
Iridoids are commonly found in plants belonging to the Scrophulariaceae family and shanzhiside methyl ester has also been isolated from A. indivisum, a related Aptosimum species. Many plants from the Scrophulariaceae family have been used as traditional medicine to treat wounds. The crude extract of the plant tested positive for antitumor activity against three cell lines, namely melanoma, breast and renal. G. bippinatum belongs to one of the largest plant families, Asteraceae and the crude extract exhibited antimicrobial activity against several microorganisms.
Prof. F.R. van Heerden