The transport of the Rooibos tea flavonoid aspalathin across the skin and the intestinal epithelium
Date
2008-03-18T08:05:03Z
Authors
Huang, Miao-Juei
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Abstract
ABSTRACT
The aqueous extract of rooibos has been used for more than three hundred years since its
discovery by the indigenous people. Currently, rooibos is gaining popularity in the
cosmetic industry and incorporation of rooibos extracts in topical cosmetic formulations
has become a fashionable trend. Both topical and intestinal absorption of rooibos tea were
investigated. The transport of aspalathin in the unfermented (green) rooibos aqueous
extracts and aqueous solution of pure aspalathin were studied.
The percutaneous permeation experiments were conducted with vertical Franz diffusion
cells using human female abdominal skin obtained from patients who underwent
cosmetic surgery. The green rooibos extract and pure aspalathin solution buffered in
phosphate buffer system (pH 5.5) were applied to the skin for 12 hours. Samples of the
permeants were obtained from the receptor fluid phase and from the stratified layers of
the skin by using the tape-stripping technique and analysed by HPLC.
In vitro intestinal epithelial transport experiments were carried out by using Caco-2 cell
monolayers, isolated and cultured from human colonic adenocarcinoma cells, in a
six-well transwell system. The green rooibos extract and pure aspalathin solution
buffered in phosphate buffer (pH 7.4) were applied on to the cell monolayers and
incubated for 2 hours. Samples were obtained from the basolateral phase at
predetermined time intervals and analysed by HPLC.
Less than 0.1 % of the applied dose of aspalathin permeated the skin. Most of the
permeated aspalathin accumulated in the stratum corneum. Close to 100 % of aspalathin
was transported across the Caco-2 cell monolayers at a concentration dependent manner.
Better absorption of aspalathin was observed using the green rooibos extract than with
the pure aspalathin solution across the Caco-2 cell monolayers.