Tandeka Unathi Magcwebeba1, Sylvia Riedel2, Sonja Swanevelder3, Pieter Swart1, Dalene De Beer4, Elizabeth Joubert4,5, Wentzel Christoffel Andreas Gelderblom6,7. 1. Department of Biochemistry, Stellenbosch University, Stellenbosch, South Africa. 2. Biomedical Research and Innovation Platform, South African Medical Research Council, Tygerberg, South Africa. 3. Biostatistics Unit, South African Medical Research Council, Tygerberg, South Africa. 4. Agricultural Research Council, Infruitec-Nietvoorbij, Stellenbosch, South Africa. 5. Department of Food Science, Stellenbosch University, Stellenbosch, South Africa. 6. Department of Biochemistry, Stellenbosch University, Stellenbosch, South Africa. gelderblomw@cput.ac.za. 7. Institute of Biomedical and Microbial Biotechnology, Cape Peninsula University of Technology, Bellville, South Africa. gelderblomw@cput.ac.za.
Abstract
OBJECTIVES: The relationship between polyphenol constituents, antioxidant properties of aqueous and methanol extracts of green tea (Camellia sinensis), the herbal teas, rooibos (Aspalathus linearis) and honeybush (Cyclopia spp.), against skin cell viability was investigated in vitro. METHODS: The effect of extracts, characterised in terms of polyphenol content and antioxidant properties, on cell viability of premalignant, normal and malignant skin cells was determined. KEY FINDINGS: Phenolic composition, particularly high levels of potent antioxidants, of rooibos and green tea methanol extracts was associated with a strong reduction in cell viability specifically targeting premalignant cells. In contrast, the aqueous extracts of Cyclopia spp. were more effective in reducing cell viability. This correlated with a relatively high flavanol/proanthocyanidin content and ABTS radical cation scavenging capacity. The major green tea flavanol (epigallocatechin gallate) and rooibos dihydrochalcone (aspalathin) exhibited differential effects against cell viability, while the major honeybush xanthone (mangiferin) and flavanone (hesperidin) lacked any effect presumably due to a cytoprotective effect. The underlying mechanisms against skin cell viability are likely to involve mitochondrial dysfunction resulting from polyphenol-iron interactions. CONCLUSIONS: The polyphenol constituents and antioxidant parameters of herbal tea extracts are useful tools to predict their activity against skin cell survival in vitro and potential chemopreventive effects in vivo.
OBJECTIVES: The relationship between polyphenol constituents, antioxidant properties of aqueous and methanol extracts of green tea (Camellia sinensis), the herbal teas, rooibos (Aspalathus linearis) and honeybush (Cyclopia spp.), against skin cell viability was investigated in vitro. METHODS: The effect of extracts, characterised in terms of polyphenol content and antioxidant properties, on cell viability of premalignant, normal and malignant skin cells was determined. KEY FINDINGS: Phenolic composition, particularly high levels of potent antioxidants, of rooibos and green tea methanol extracts was associated with a strong reduction in cell viability specifically targeting premalignant cells. In contrast, the aqueous extracts of Cyclopia spp. were more effective in reducing cell viability. This correlated with a relatively high flavanol/proanthocyanidin content and ABTS radical cation scavenging capacity. The major green tea flavanol (epigallocatechin gallate) and rooibos dihydrochalcone (aspalathin) exhibited differential effects against cell viability, while the major honeybushxanthone (mangiferin) and flavanone (hesperidin) lacked any effect presumably due to a cytoprotective effect. The underlying mechanisms against skin cell viability are likely to involve mitochondrial dysfunction resulting from polyphenol-iron interactions. CONCLUSIONS: The polyphenol constituents and antioxidant parameters of herbal tea extracts are useful tools to predict their activity against skin cell survival in vitro and potential chemopreventive effects in vivo.