title: In Vitro Chemopreventive Properties of Green Tea, Rooibos and Honeybush Extracts in Skin Cells.
abstract: The chemopreventive properties of the herbal teas rooibos (Aspalathus linearis) and honeybush (Cyclopiaspp.) have been demonstrated on mouse skin in vivo but the underlying mechanisms are not clear. The aim of the current study was to determine the anti-proliferative and pro-apoptotic activity of methanol and aqueous extracts of rooibos and twoCyclopiaspecies in different skin cells, using green tea (Camellia sinensis) as a benchmark. Extracts were also characterised for their major individual polyphenols by high performance liquid chromatography and spectroscopically for the total polyphenol (TP) groups. The methanol extract of rooibos, containing higher levels of polyphenols than its aqueous extract, displayed similar activity to green tea as it selectively targeted premalignant cells by inhibiting cell proliferation at lower concentrations whilst inducing apoptosis via membrane depolarisation at higher concentrations. Specific roles of the major rooibos dihydrochalcones and flavanol/proanthocyanidin-type (FLAVA) compounds are likely to be involved. The aqueous extracts of theCyclopiaspecies were more active against cell proliferation and at inducing apoptosis which was associated with a higher FLAVA content and a reduced TP/FLAVA ratio. In contrast, their methanol extracts exhibited a cytoprotective effect against apoptosis which was related to their monomeric xanthone and flavanone content. The underlying chemopreventive properties of green tea and the herbal teas appear to be associated with diverse and complex monomeric/polymeric polyphenolic cell interactions.
authors.affiliation: Department of Biochemistry, Stellenbosch University, Private Bag X1, Matieland (Stellenbosch) 7602, South Africa. tmagcwebeba@sun.ac.za.
authors.forename: Tandeka U
authors.initials: TU
authors.lastname: Magcwebeba
authors.affiliation: Department of Biochemistry, Stellenbosch University, Private Bag X1, Matieland (Stellenbosch) 7602, South Africa. pswart@sun.ac.za.
authors.forename: Pieter
authors.initials: P
authors.lastname: Swart
authors.affiliation: Biostatistics Unit, South African Medical Research Council, P.O. Box 19070, Tygerberg 7505, South Africa. sonja.swanevelder@mrc.ac.za.
authors.forename: Sonja
authors.initials: S
authors.lastname: Swanevelder
authors.affiliation: Post-Harvest and Wine Technology Division, Agricultural Research Council (Infruitec-Nietvoorbij), Private Bag X5026, Stellenbosch 7599, South Africa. joubertL@arc.agric.za.|Department of Food Science, Stellenbosch University, Private Bag X1, Matieland (Stellenbosch) 7602, South Africa. joubertL@arc.agric.za.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Joubert
authors.affiliation: Department of Biochemistry, Stellenbosch University, Private Bag X1, Matieland (Stellenbosch) 7602, South Africa. gelderblomw@cput.ac.za.|Institute of Biomedical and Microbial Biotechnology, Cape Peninsula University of Technology, P.O. Box 1906, Bellville 7535, South Africa. gelderblomw@cput.ac.za.
authors.forename: Wentzel C A
authors.initials: WC
authors.lastname: Gelderblom
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D036903:Aspalathus / Q000737:chemistry*; D049109:Cell Proliferation / Q000187:drug effects; D018890:Chemoprevention; D007887:Fabaceae / Q000737:chemistry*; D005434:Flow Cytometry; D066298:In Vitro Techniques; D010936:Plant Extracts / Q000494:pharmacology*; D012867:Skin / Q000166:cytology / Q000187:drug effects*; D013662:Tea / Q000737:chemistry*
chemical_list: D010936:Plant Extracts; D013662:Tea
keywords: anti proliferative; flavanols; herbal teas; pro-apoptotic; skin cancer