Biological activity of different Inonotus species on human keratinocytes

Various fungi are known for their biological activities in men and thus are used as medicinal mushrooms. Inonotus obliquus, the Chaga mushroom, for example was widely used in folk medicine in Russia and western Siberia. The observed anti-oxidative, anti-inflammatory and anti-cancer effects have been attributed in part to styrylpyrones. In comparison to this hispolon and hispidin isolated from Inonotus hispidus showed also antiviral activity. But there is only little knowledge about the biological activity of two other Inonotus species, namely Inonotus nodulosus and Inonotus dryadeus. The aim of this study was to investigate the effects of fruiting body extracts of these four Inonotus species on a human keratinocyte cell line (HaCaT) to detect possible skin protective properties. All tested extracts showed a dose dependent activity on human keratinocytes. Treatment with aqueous and ethanolic extracts of I. obliquus or I. dryadeus resulted in a dose dependent decrease in cell viability. In contrast to that treatment with I. nodulosus or I. hispidus had a slightly stimulating effect on HaCaT cell viability. The ethanolic I. nodulosus extract was also able to reduce a serum deprivation induced G₀/G₁ cell cycle arrest by 20%. Cells stressed by UVB broadband irradiation (20 mJ/cm²) showed a strong cell cycle arrest in G₂/M phase. Incubation with aqueous I. hispidus or ethanolic I. nodulosus extract after irradiation reduced this effect. The study clearly shows that Inonotus species especially Inonotus hispidus and Inonotus nodulosus are promising candidates for both skin cosmetics and active natural compound research.