Anti-UV activity of Kampo medicines and constituent plant extracts: re-evaluation with skin keratinocyte system.

Abstract

AIM: In order to search for new biological activity of Kampo medicines and their constituent plant extracts, we investigated their ability to protect the cells from UV irradiation (referred to as 'anti-UV activity') using the human immortalised skin keratinocyte cell line HaCaT. MATERIALS AND METHODS: Anti-UV activity was represented by the selectivity index (SI), defined as the ratio of the concentration that reduced the viable cell number by 50% to the concentration that increased the viability of UV-irradiated cells to 50%. RESULTS: HaCaT cells were highly resistant to UV irradiation, approximately 20% of cells survived even when the exposure time was prolonged to 480 min. Sodium ascorbate, a popular antioxidant, used as positive control, had excellent anti-UV activity (SI=200). Among 10 Kampo medicines, Shosaikoto (SI=34) had the highest anti-UV activity, followed by Hangesyashinto (SI>28), Unseiin (SI>23) and Ninjinyoeito (SI=23), Saireito (SI>19), whereas another four Kampo medicines were much less active (SI<9.6). Among 25 constituent plant extracts, Scutellaria root had the highest anti-UV activity (SI=38), followed by Polyporus sclerotium (SI>26), Gardenia fruit (SI>23), Japanese Gentian (SI>20) and Saposhnikovia root (SI>20). Glycyrrhizin also had potent anti-UV activity (SI=36). The SI values determined with the present HaCaT system were generally one order higher than those obtained with previously reported HSC-2 human oral squamous cell carcinoma system, although there was good correlation between these two systems (R(2)=0.9118). Conclusion. The present study highlights the improved sensitivity of anti-UV activity detection with the HaCaT system, and suggests the possible application of Kampo medicines as a component of sunscreening cosmetics.