Dose-dependent vitamin C uptake and radical scavenging activity in human skin measured with in vivo electron paramagnetic resonance spectroscopy.

Vitamin C is a potent radical scavenger and a physiological part of the antioxidant system in human skin. The aim of this study was to measure changes in the radical-scavenging activity of human skin in vivo due to supplementation with different doses of vitamin C and at different time points. Therefore, 33 volunteers were supplemented with vitamin C or placebo for 4 weeks. The skin radical-scavenging activity was measured with electron paramagnetic resonance spectroscopy. After 4 weeks, the intake of 100 mg vitamin C/day resulted in a significant increase in the radical-scavenging activity by 22%. Intake of 180 mg/day even resulted in a significant increase of 37%. No changes were found in the placebo group. A part of the study population was additionally measured after 2 weeks: in this group radical scavenging had already reached maximal activity after 2 weeks. In conclusion, orally administered vitamin C increases the radical-scavenging activity of the skin. The effect occurs fast and is enhanced with higher doses of vitamin C.

Radical protection in the visible and infrared by a hyperforin-rich cream--in vivo versus ex vivo methods.

The formation of radicals plays an important role in the development of atopic eczema or barrier-disrupted skin. We evaluated the radical scavenging effect of a cream containing a Hypericum perforatum extract rich in hyperforin in a double-blind placebo-controlled study on 11 healthy volunteers. Electron paramagnetic resonance spectroscopy was applied to determine radical formation during VIS/NIR irradiation of the inner forearm. The results were compared to ex vivo investigations on excised porcine ear skin after a single application of the creams. The non-treated skin was measured as control. The absolute values and the kinetics are not comparable for ex vivo and in vivo radical formation. Whereas in vivo, the radical production decreases with time, it remains stable ex vivo over the investigated timescale. Nevertheless, ex vivo methods could be developed to estimate the protection efficiency of creams. In vivo as well as ex vivo, the radical formation could be reduced by almost 80% when applying the hyperforin-rich cream onto the skin, whereas placebo resulted in about 60%. In vivo, a daylong protection effect could be validated after a 4-week application time of the cream indicating that a regular application is necessary to obtain the full effect.

In vivo photoprotective and anti-inflammatory effect of hyperforin is associated with high antioxidant activity in vitro and ex vivo.

Hyperforin, a major constituent of St. John's Wort (Hypericum perforatum, HP), provides anti-inflammatory, anti-tumor, and anti-bacterial properties. Previous studies have shown anti-oxidative properties of St. John's Wort extracts; however, its free radical scavenging activity in skin cells or skin has not been assessed in detail so far. Therefore, the free radical scavenging activity of hyperforin was tested in the H(2)DCFDA-assay in vitro in HaCaT keratinocytes irradiated with solar simulated radiation. Hyperforin (EC(50) 0.7 µM corresponding to 0.42 µg/ml) was much more effective compared to Trolox (EC(50) 12 µg/ml) and N-acetylcysteine (EC(50) 847 µg/ml) without showing phototoxicity. The radical protection factor of a cream containing 1.5%w/w of a hyperforin-rich HP extract was determined to be 200 × 10(14) radicals/mg, indicating a high radical scavenging activity. The cream was further applied ex vivo on porcine ear skin and significantly reduced radical formation after infrared irradiation. Finally, the UV-protective effect of the HP cream was tested on 20 volunteers in a randomized, double-blind, vehicle-controlled study. HP cream significantly reduced UVB-induced erythema as opposed to the vehicle. Occlusive application of HP cream on non-irradiated test sites did not cause any skin irritation. Taken together, these results demonstrate that hyperforin is a powerful free radical scavenger.

Determination of the influence of IR radiation on the antioxidative network of the human skin.

Production of free radicals in the human skin subsequent to IR irradiation has been demonstrated by means of two different methods. The first technique, based on resonance Raman spectroscopy, enables the non-invasive measurements of the kinetics of cutaneous carotenoid antioxidants beta-carotene and lycopene, subsequent to IR irradiation. Obtained degradation of the cutaneous carotenoids was a hint but not evidence that IR irradiation can produce free radicals in the skin. Therefore, the direct observation sustaining the production of free radicals subsequent to IR irradiation in the skin was performed in-vitro by electron paramagnetic resonance spectroscopy. Enzymatic processes as well as heat shock-induced radicals in the human skin are presumably involved in the energy transfer from IR irradiation into the molecules of the skin. Protection strategy for human skin against IR-induced free radicals based on the increase in the concentration of antioxidants by means of antioxidant-rich supplementation is discussed.