Free-radical-scavenging and tyrosinase-inhibition activities of Cheonggukjang samples fermented for various times

Methanol extracts of Cheonggukjang, fermented for various times, were evaluated for their free-radical-scavenging and tyrosinase-inhibitory activities and the underlying mechanisms were elucidated. The free-radical-scavenging activity was highest for Cheonggukjang extracts fermented for 40 h and this decreased as the fermentation time shortened. The tyrosinase-inhibition activity increased with the length of fermentation. While levels of total phenolic compounds were highest in the 40-h-fermented Cheonggukjang samples, the total flavonoid content was lower compared to samples fermented for shorter times. Therefore, the antioxidative and tyrosinase-inhibition activities exhibited by methanol-extracted Cheonggukjang samples may be attributable to the contents of total phenolic compounds.