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Modulation of ultrviolet light induced skin carcinogenesis by extracts of Rooibos and Honeybush using a mouse model:elucidating possible protective mechanisms
Author(s)
Petrova, Antoinette
Date Issued
2009
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
This thesis provides the first scientific evidence of the photoprotective properties of rooibos
and honeybush herbal tea extracts and to some extent, two major honeybush polyphenols,
hesperidin and mangiferin. These properties were demonstrated using in vivo models by:
Providing evidence for the inhibition of tumour promotion by ultraviolet B (UVB)
radiation in a two-stage skin carcinogenesis mouse model. Topical application of
polyphenol-rich extracts of rooibos and honeybush prior to UVB tumour promotion of
7,12-dimethylbenz[a]anthracene (DMBA)-initiated mouse skin, inhibited the formation
of tumours. The rooibos and honeybush extracts decreased the incidence and volume
of the tumours. Topical application of hesperidin and mangiferin were less effective
than the honeybush extracts as only the tumour volume was decreased, but not the
incidence.
Providing evidence for the inhibition of photodamage of the skin by UVB exposure in a
mouse model. Topical application of polyphenolic rich extracts of honeybush prior to
UVB irradiation of mouse skin reduced erythema, peeling, oedema and hyperplasia.
The depletion of antioxidant enzymes catalase and superoxide dismutase (SOD) was
prevented. The extracts protected the skin from oxidative and direct DNA damage, and
reduced lipid peroxidation. The induction of cyclooxygenase-2 (COX-2) and ornithine
decarboxylase (ODC) was also reduced. Topical application of the polyphenols
hesperidin and mangiferin showed reduced protective effects compared to the extracts.
Suggesting the possible mechanisms by which honeybush and the polyphenols protect
against photocarcinogenesis such as reducing tumour promotion, inflammation and
oxidative stress.
Suggesting the benefits of including honeybush and rooibos as cosmeceuticals in skin
care products and sunscreens as part of the strategy for preventing skin cancer.
Discussing the recommendations for further study such as investigating more specific
chemopreventive activities of these two South African herbal teas and their
polyphenols, dose response studies and clinical evaluations.
and honeybush herbal tea extracts and to some extent, two major honeybush polyphenols,
hesperidin and mangiferin. These properties were demonstrated using in vivo models by:
Providing evidence for the inhibition of tumour promotion by ultraviolet B (UVB)
radiation in a two-stage skin carcinogenesis mouse model. Topical application of
polyphenol-rich extracts of rooibos and honeybush prior to UVB tumour promotion of
7,12-dimethylbenz[a]anthracene (DMBA)-initiated mouse skin, inhibited the formation
of tumours. The rooibos and honeybush extracts decreased the incidence and volume
of the tumours. Topical application of hesperidin and mangiferin were less effective
than the honeybush extracts as only the tumour volume was decreased, but not the
incidence.
Providing evidence for the inhibition of photodamage of the skin by UVB exposure in a
mouse model. Topical application of polyphenolic rich extracts of honeybush prior to
UVB irradiation of mouse skin reduced erythema, peeling, oedema and hyperplasia.
The depletion of antioxidant enzymes catalase and superoxide dismutase (SOD) was
prevented. The extracts protected the skin from oxidative and direct DNA damage, and
reduced lipid peroxidation. The induction of cyclooxygenase-2 (COX-2) and ornithine
decarboxylase (ODC) was also reduced. Topical application of the polyphenols
hesperidin and mangiferin showed reduced protective effects compared to the extracts.
Suggesting the possible mechanisms by which honeybush and the polyphenols protect
against photocarcinogenesis such as reducing tumour promotion, inflammation and
oxidative stress.
Suggesting the benefits of including honeybush and rooibos as cosmeceuticals in skin
care products and sunscreens as part of the strategy for preventing skin cancer.
Discussing the recommendations for further study such as investigating more specific
chemopreventive activities of these two South African herbal teas and their
polyphenols, dose response studies and clinical evaluations.
Additional information
Thesis(M Tech(Biomedical Technology))--Cape Peninsula University of Technology, 2009
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