Enhancement of Melanogenic Inhibitory Effects of the Leaf Skin Extracts of Aloe barbadensis Miller by the Fermentation Process

Abstract

This work first showed that the skin-lightening effects of the leaf skin extracts of Aloe vera were significantly increased by the fermentation of Lactobacillus plantarum BN41. The fermented extract (BF) showed much higher antioxidant activities of DPPH scavenging effects and the reduction in intracellular ROS production than the water extract (BW), and even higher than Trolox as a positive control. High efficacy of the BF results was shown from the synergistic effects of higher elution of aloesin (2.96 ± 0.09 mg/g vs. 2.03 ± 0.02 mg/g in BF and BW, respectively) and bioactive substances from the fermentation processes. The inhibition of tyrosinase activities and melanin synthesis at 0.3% (w/v) optimal dosage of BF was much better than those of arbutin and aloesin, which are commercial skin-lightening ingredients. It was also first proved that BF effectively down-regulated all microphthalmia-associated transcription factors (MITF), tyrosinase-related protein-1 (TYRP-1) and TYRP-2, and tyrosinase (TYR) gene expression (p < 0.05), proposing melanogenesis inhibitory mechanism in the MITF/TYRP-1/TYRP-2/TYR pathway. However, aloesin and arbutin selectively suppressed the expression of TRYP-1, TRYP-2 or TYR. It was clearly demonstrated that the fermentation process reduces inherent cytotoxicity of aloe, showing much less cell cytotoxicity than BW. Conclusively, 0.3% (w/v) of the BF can be utilized as a competitive and sustainable natural skin-lightening ingredient.