Coffee based polyphenols with potential in skin care
Antioxidant activity and skin penetration assessed by in vivo Raman spectroscopy
Active ingredients of plant origin such as polyphenols and phenolic acids are enjoying increased acceptance in both the food and cosmetics industries. Their often excellent antioxidant properties are determined by in vitro assays. To develop an effective skin care formulation, their penetration ability and bioavailability has to be investigated as well. Both depend on molecular size, but also on the molecules’ balance of lipo- and hydrophilicity. In this paper, the antioxidant activity of individual coffee fractions (roasted and unroasted) is compared by means of in vitro antioxidant assays, and the influence of the formulation on skin penetration of the antioxidant active is examined by in vivo Raman spectroscopy.
Polyphenols and in-situ (roasting) reaction products
Polyphenols belong to one of the most interesting classes of compounds in nature with antioxidative potential. While they occur in plant materials such as tea, cocoa, coffee, herbs and phytochemicals, coffee as beverage has been shown by an LDL oxidation assay to have among the highest contents (1). Polyphenols have been claimed to have health-promoting effects like anti-oxidant, anti-microbial, anti-viral, anti-aging, anti-thrombotic and anti-allergic, also govern cellular processes and have metal chelating functions. Although the specific mechanisms responsible for the effective and cumulative health-promoting effects are not yet clear, there is an observed correlation between an intake of anti-oxidants and health benefits (2). Polyphenols used in skin treatment include tea polyphenols (like epicatechin), silymarin, quercetin, resveratrol and tannins (hydrolysable and condensed substances such as proanthocyanidins). However, smaller molecules such as phenolic acids like caffeic acid and ferulic acid are also used in anti-aging skin care (3).