Background: Using our recently established simple method for evaluating protective activity from ultraviolet ray injury (referred to as 'anti-UV activity'), the effectiveness of various antioxidants and plant extracts was investigated.
Materials and methods: HSC-2 human oral squamous cell carcinoma cells were exposed to UV irradiation (wavelength: 253.7 nm, 6 J/m²) in phosphate-buffered saline (PBS(-)) containing various concentrations of samples and then incubated for 48 hours in regular culture medium to determine the viable cell number by the MTT method.
Results: Among the representative antioxidants, sodium ascorbate showed the most potent anti-UV activity, whereas catalase and N-acetyl-L-cysteine were inactive. Lentinus edodes mycelia extract (LEM) showed comparable anti-UV activity to sodium ascorbate. Hot water extracts of green tea and coffee, and PET-bottled of green tea extract showed slightly less, but noticeable anti-UV activity. On the other hand, hot water extracts of black tea and Jasmine tea, and PET-bottled of oolong tea, barley tea and Kohki tea were inactive. LEM was separated by gel filtration chromatography into four fractions from high to low molecular weight: polysaccharide, large and small lignin-carbohydrate complexes, and sugars. Anti-UV activity was shown by the lignin-carbohydrate fractions, but not the polysaccharide and sugar fractions. LEM, at high concentration, slightly enhanced the anti-UV activity of sodium ascorbate.
Conclusion: LEM may be applicable as a UV-protective agent.