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

Abstract

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.

Determination of the Antioxidant Status of the Skin by In Vivo-Electron Paramagnetic Resonance (EPR) Spectroscopy

“…The topical application of antioxidants is therefore a promising tool to reduce the radical overload in the skin. Moreover, daily skin care is essential to maintain the skin barrier or to support its regeneration [64]. Hyperforin provides anti-inflammatory, antitumor and antibacterial properties and is a major constituent of St. John's Wort (Hypericum perforatum) [65,66].…”

“…It also reduces the free radical formation in the skin after exposure to UV and IR radiation [42]. In our studies, the protection effect of topically applied antioxidants was examined compared to increased radical formation in skin induced by VIS/NIR irradiation via the EPR marker PCA [40,64].…”

“…A hyperforin-rich cream was analyzed for its radical protection in the skin after VIS/NIR irradiation and compared to untreated skin and placebo samples [40,64]. Eleven volunteers with healthy skin were examined after a single, and further four-week cream application.…”

“…Taking into consideration the risk of erythema development, the formation of free radicals in the radiation-exposed skin can only be investigated for a limited time, in vivo. Thus ex vivo experiments are very helpful in understanding the kinetics of radical formation during irradiation, because the samples do not have to be removed for erythema development [64]. In dermatology, pig ear skin is commonly used as a human skin model [74].…”

“…In dermatology, pig ear skin is commonly used as a human skin model [74]. With the EPR technology, it is possible to measure the radical formation in skin in vivo as well as ex vivo [38,64]. In our study, the radical protection of skin in the visible and infrared spectral range by a hyperforin-rich cream was studied in vivo vs. ex vivo, non-treated skin was measured as control [64].…”