Method development and application for the assessment of the antiageing and antioxidant properties of herbal remedies

Thring, Tamsyn S. A. (2012) Method development and application for the assessment of the antiageing and antioxidant properties of herbal remedies. (PhD thesis), Kingston University, .


The role of reactive oxygen species and proteinases involved in the destruction of the extra-cellular matrix, microbial infection and inflammation have been shown as key factors influencing the skin ageing process. Many herbal extracts and natural compounds have shown promising activity in neutralising free radicals, preventing oxidative stress and acting as inhibitors of proteinases involved in cellular degradation and this evidence provides the platform for this study. The main aim of this study was to develop a panel of assays which would enable the broad screening of a large variety of herbal extracts, individual product ingredients and whole products for their antimicrobial, antioxidant, and antiageing activities. Over 100 herbal extracts from 37 different plant families were screened at several concentrations in 5 main bioassays. Antioxidant activity of each extract was assessed utilising 3 assays. The gallic acid equivalent assay to assess phenolic content, the trolox equivalent antioxidant capacity assay to demonstrate and rank anti-radical activity, and the superoxide dismutase mimetic activity assay to assess for catalytic antioxidant activity. For antiageing evaluation, two assays incorporating 2 ageing associated enzymes; collagenase and elastase were employed. Thin-layer chromatography was used to demonstrate antioxidant activity for extracts not soluble in the three antioxidant assays and, for similar reasons, a new TLC method was developed to demonstrate anti-collagenase activity for commercial products and problematic extracts. A white tea (WT) extract demonstrated the most desirable activity in all assays. Other extracts which performed particularly well include green tea (GT), witch hazel (WH), rose (R), rooibos tea (RB) and mahonia. Several whole commercial products containing WT and WH also demonstrated promising activities. Cell-based assays involving the effects of the 5 extracts and 2 products above and their activity against H[sub]20[sub]2 induced oxidative stress on human dermal fibroblasts were then implemented. The WT again demonstrated powerful protective effects on the cells and prevented the secretion of the inflammatory cytokine interleukin-8. These results demonstrate that plant extracts have the potential to act as antioxidant, anti ageing and anti-inflammatory ingredients in formulations. The factors involved in skin-ageing are also significant contributors in several inflammatory diseases therefore further investigation of active extracts may prove beneficial for future treatments.

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