UV-protecting potential of clay minerals and Ganoderma pfeifferi
Exposure with ultraviolet radiation (UV) results in aging of skin and is a leading cause of skin cancer. The cellular responses to UV radiation have received considerable attention over the last few years. Because of the possible phototoxicity of the common physical UV-filter substance titanium dioxide  we searched for natural products with UV protecting activities.
For our tests we used the human keratinocyte cell line HaCaT  and 20 mJ/cm2 UVB for irradiation. Cells were covered with a quartz plate coated with 1mg/cm2 clay mineral (FIM Biotech) plus Ganoderma pfeifferi nanoparticles or commercial suntan lotion (containing TiO2) during irradiation. In a second experiment cells were incubated with ethanolic Ganoderma pfeifferi extract (10µg/ml) after UVB-irradiation. All supernatants of treated cells were then tested for free lactate dehydrogenase (LDH) activity. High values of this intracellular enzyme correspond to cellular damage.
Control cells irradiated with 20mJ/cm2 UVB showed altered morphology and high levels of LDH activity (2.92 mU/cm2=100%). As expected, HaCaT cells were protected against UV damage by suntan lotion (13% of treated control). The treatment with clay mineral plus Ganoderma exhibited comparable shielding effects (28%). Curative treatment with Ganoderma extract alone led to reduced LDH release as well (40%).
Our results show that clay minerals can be used as physical sunscreens and can be alternatives for TiO2. Shielding effects can be increased by addition of extracts acting as UV filters or radical scavengers. As Ganoderma pfeifferi extract is active at both sites it might be the ideal supplement and demonstrate that natural products are a potential source for skin-protecting or antiaging formulations.
References: 1. Hirakawa, K. et al. (2004) Free Radical Res 38: 439–47
2. Boukamp, P. et al (1988)J Cell Biol 106: 761–71