Application of FTIR microspectroscopy for characterization of biomolecular changes in human melanoma cells treated by sesamol and kojic acid

BackgroundHyperpigmentation is aesthetic undesirable. Sesamol and the standard antimelanogenic agent (kojic acid) were shown to hinder melanogenesis by blocking tyrosinase and reducing melanin content.ObjectiveThe FTIR microspectroscopy was used in an attempt to find a novel method to define biological alternation in a melanogenesis inhibition of sesamol and kojic acid.MethodsTyrosinase inhibition and melanin content of sesamol and kojic acid were evaluated. The FTIR microspectroscopy was adopted to define the vibrational characteristic involved with the melanogenesis in the untreated SK-MEL2 cells vs. the sesamol- and kojic-treated SK-MEL2 cells.ResultsSesamol and kojic acid inhibited mushroom tyrosinase at IC50 of 0.33 μg/ml and 6.1 ± 0.4 μg/ml, respectively. Moreover, 30 μg/ml sesamol inhibited 23.55 ± 8.25% cellular tyrosinase activity in human SK-MEL2 cells, while 600 μg/ml kojic acid inhibited 33.9 ± 1.4% cellular tyrosinase activity in the same cells. In the SK-MEL2-treated with two inhibitors, the FTIR spectra assigned to the lipid and nucleic acid bands were significantly depleted with the secondary protein structure shifted to a more β-pleated secondary protein one.ConclusionBoth sesamol and kojic acid display a similar pattern of antimelanogenesis activity albeit to a different degree. The mechanism of their whitening effect may be via the alteration of (a) the enzyme conformation disallowing the ordinary enzyme–substrate interaction and maybe (b) the integrity of the lipid-containing melanosome. Our results support the alternative use of FTIR microspectroscopy as a simple and reagent-free method for characterization of biomolecular changes in human melanoma cells.