title: An unusual 2,3-secotaraxerene and other cytotoxic triterpenoids from Pleiocarpa pycnantha (Apocynaceae) leaves collected from Nigeria.
abstract: Three known triterpenoids, namely ursolic acid (1), and the 27-E- and 27-Z-p-coumaric esters of ursolic acid (compounds 2, 3), were isolated together with a new triterpene 2,3-seco-taraxer-14-en-2,3-lactone [pycanocarpine (4)] from an ethanolic extract of Pleiocarpa pycnantha leaves. The structure of 4 was unambiguously assigned using NMR, HREIMS and X-ray crystallography. The cytotoxic activities of the compounds were evaluated against HeLa, MCF-7, KMST-6 and HT-29 cells using the WST-1 assay. Ursolic acid (1) displayed potent cytotoxic activity against HeLa, HT-29 and MCF-7 cells with IC₅₀ values of 10, 10 and 20 µM respectively. The new compound 4 and its hydrolysed derivative 5 were selectively cytotoxic to the breast cancer cell line, MCF-7 with IC₅₀ values 20 and 10 µM respectively. This is the first report on isolation of a 2,3-seco-taraxerene derivative from the Apocynaceae family and cytotoxic activity of P. pycnantha constituents.
authors.affiliation: Department of Chemistry, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa.
authors.forename: Olubunmi A
authors.initials: OA
authors.lastname: Omoyeni
authors.affiliation: Department of Biotechnology, Apoptosis Research Unit, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa.
authors.forename: Mervin
authors.initials: M
authors.lastname: Meyer
authors.affiliation: Department of Chemistry, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Iwuoha
authors.affiliation: Department of Chemistry, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa.
authors.forename: Ivan
authors.initials: I
authors.lastname: Green
authors.affiliation: Department of Chemistry, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa. ahmohammed@uwc.ac.za.
authors.forename: Ahmed A
authors.initials: AA
authors.lastname: Hussein
mesh_terms: D029062:Apocynaceae / Q000737:chemistry*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D020128:Inhibitory Concentration 50; D015394:Molecular Structure; D009549:Nigeria; D019906:Nuclear Magnetic Resonance, Biomolecular; D010936:Plant Extracts / Q000737:chemistry*; D018515:Plant Leaves / Q000737:chemistry*; D014315:Triterpenes / Q000737:chemistry* / Q000633:toxicity*
chemical_list: D010936:Plant Extracts; D014315:Triterpenes