Biotransformation of isocostic acid from Dittrichia viscosa essential oil by Saccharomyces cerevisiae: in vitro anti-tyrosinase effect, insights from molecular docking and drug-likeness prediction

The purpose of this study was to investigate the biotransformation of the essential oil of Dittrichia viscosa leaves (LEO) by Saccharomyces cerevisiae (baker's yeast) and to evaluate its anti-tyrosinase property. The chemical analysis of the biotransformed essential oil (BEO) was determined by GC-FID and GC/MS. The results showed that isocostic acid, the predominant constituent of LEO (70.8%) was found to be totaly converted by S. cerevisiae into its isomer valerenic acid representing 78.4% of the total composition of BEO. The biotransformed essential oil (BEO) exhibited promising anti-tyrosinase activity (IC50 = 8.54 mu g/mL) six times greater than that of LEO (IC50 = 53.44 mu g/mL). The experimental results were reinforced by the molecular docking analysis and drug-likeness prediction carried out on the two major sesquiterpene acids detected in LEO and BEO (isocostic acid and valerenic acid, respectively). Valerenic acid showed lower binding energy (-6.3 kcal/mol) compared to isocostic acid (-5.9 kcal/mol), a correct mode and a large number of interactions in the active pocket of the enzyme which can explain the strong inhibitory effect of tyrosinase. Therefore, these results suggest that the bioconverted essential oil could be regarded as safe and effective source of skin whitening agent for cosmetic and medical applications.