Phytochemical analysis of Cyrtanthus obliquus bulbs from the informal street market of Kwazulu-Natal, South Africa
Background: Cyrtanthus obliquus is a medicinal plant commonly known by the locals in South Africa as Umathunga. It is used in traditional South African medicine for the treatment of scrofula, chronic coughs and headaches and is also used to prepare the popular decoction known as Imbiza.
Materials and methods: The secondary metabolites from C. obliquus bulbs were extracted using solvent extraction techniques, isolated using column chromatography and identified using spectroscopic techniques. The antioxidant potential of the isolated compounds was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and the ferric reducing antioxidant potential (FRAP) assay.
Results: The extracts yielded four homoisoflavonoids, 5,7-dihydroxy-6-methoxy-3-(4ꞌ-Methoxybenzyl)chroman-4-one, 5,7-dihydroxy-3-(4ꞌ- hydroxybenzyl)chroman-4-one,5,7-dihydroxy-6-methoxy-3-(4ꞌ-methoxybenzylidene)chroman-4-one and 5,7-dihydroxy-3-(4ꞌ- hydroxybenzylidene)chroman-4-one. An unusual 3-β-glucopyranosyl-22,27-dihydroxy-lanosta-8-ene was also isolated from the bulbs. The antioxidant studies showed that 3-benzylchromanones have better activity than 3-benzylidenechromanones.
Conclusion: Four homoisoflavanones namely 5,7-dihydroxy-6-methoxy-3-(4ꞌ-methoxybenzyl)chroman-4-one; 5,7-dihydroxy-6-methoxy-3-(4ꞌ- hydroxybenzyl)chroman-4-one and two 5,7-dihydroxy-6-methoxy-3-(4ꞌ-methoxybenzylidene)chroman-4-one; 5,7-dihydroxy-3-(4ꞌ- hydroxybenzylidene)-chroman-4-one were obtained from Cyrtanthus obliquus.
Key words: Amaryllidaceae, homoisoflavonoids, medicinal plant, traditional medicine
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