Chemical composition and tyrosinase inhibitory activity of Cinnamomum cassia essential oil

Essential oils extracted from aromatic plants exhibit important biological activities and have become increasingly important for scientific research. The essential oil extracted from Cinnamomum cassia Presl (CC-EO) has various functional properties, however, little information is available regarding the tyrosinase inhibitory activity. Therefore, the objectives of this study were to investigate the chemical composition and tyrosinase inhibitory activity of the CC-EO. cis-2-methoxycinnamic acid (43.06%) and cinnamaldehyde (42.37%) were found to be the two major components of the CC-EO identified by gas chromatography-mass spectrometry (GC-MS). The inhibitory activities of CC-EO and its major constituents were further evaluated against mushroom tyrosinase. The results showed that CC-EO and cinnamaldehyde exhibited anti-tyrosinase activities with IC50 values of 6.16 +/- 0.04 mg/mL and 4.04 +/- 0.08 mg/mL, respectively. However, cis-2-methoxycinnamic acid did not show any anti-tyrosinase activity. The inhibition kinetics were analyzed by Lineweaver-Burk plots and second replots, which revealed that CC-EO and cinnamaldehyde were mixed-type inhibitors. The inhibition constants (Ki) for CC-EO and cinnamaldehyde were calculated to be 4.71 +/- 0.09 mg/mL and 2.38 +/- 0.09 mg/mL, respectively. These results demonstrate that CC-EO and its major component, cinnamaldehyde, possess potent anti-tyrosinase activities and may be a good source for skin-whitening agents.