Background : Stevia rebaudiana (Asteraceae), a perennial plant, has been used as a low caloric sweetener and therapeutic agent for diabetes, hypertension, myocardial, and antimicrobial infections. It has been commonly used leaves and stems because of their high anti-oxidative potential. The present research was carried out to explore anti-oxidative and anti-melanogenic effects of aqueous extract of Stevia rebaudiana Bertoni flos in B16F10 cells. Methods and Results : Anti-oxidant activity of Stevia flos extract (SFE) was determined by using 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging assay, nitric oxide (NO) radical scavenging method, and reducing power method. The results showed that the total phenolic content of SFE was 63.154 ± 0.0002 ㎍·QE/100㎎ and the total flavonoid was 8.64 1 ± 0.002 ㎍·GAE/100㎎. SFE exhibited a big significant effect on NO radical scavenging activity (IC50: 179.6 ㎍/㎖) comparing with standard ascorbic acid (IC50: 368.6 ㎍/㎖), and showed concentration dependent DPPH radical scavenging activity (IC50: 131.8 ㎍/㎖). Anti-melanogenic effect of SFE was also examined with B16F10 melanocytes. The amount of melanin synthesis followed by α-melanocyte stimulating hormone on B16F10 cells were significantly reduced in the presence of SFE treatment (p < 0.05). SFE also suppressed the tyrosinase activity (p < 0.05) and α-glucosidase activity (p < 0.05). Conclusion : These results provide evidence Stevia rebaudiana flos has an antioxidant potency and can be used as an anti-melanogenic agent.

This study was conducted to investigate the quality characteristics and changes in isoflavone content of Cheonggukjang with added Chaga mushroom by secondary fermentation at 40 for 48 h with or without a starter, Lactobacillus acidophilus KCTC 3925. Cheonggukjang samples were divided into three groups: Control (unsterilized Cheonggukjang fermented without a starter), NS (unsterilized Cheonggukjang inoculated with L. acidophilus KCTC 3925), and YS (heat-sterilized Cheonggukjang inoculated with L. acidophilus KCTC 3925). The approximate composition of the three types of Cheonggukjang was 49.79-51.44% moisture, 4.54-4.72% crude ash, 43.21-44.37% crude protein, 11.58-13.65% crude fat, 37.41-40.07% carbohydrate, 31.92-33.82% dietary fiber. The mineral content included 5.43– 9.64 mg% Na, 1,792.86–1,824.39 mg% K, 253.69–326.09 mg% Ca, 619.37–691.20 mg% P, 92.59–110.59 mg% Fe, and 0.01–0.02 mg%Cd. Free amino acid contents of NS (2,520.92 mg%) and YS (2,421.94 mg%) were significantly higher than that of the control (2,236.76 mg%). Amino-type nitrogen content for the three types of Cheonggukjang ranged from 837.20-920.27 mg% with no significant difference. Ammonia-type nitrogen content ranged from 137.09-169.36 mg%. Supplement of Cheonggukjang with L. acidophilus KCTC 3925 increased production of aglycone isoflavons compared to that of control. Therefore, our results show that fermenting Chaga Cheonggukjang with L. acidophilus KCTC 3925 leads to improved quality characteristics and increased isoflavone aglycone content.