Stevia rebaudiana (Asteraceae), a perennial plant, has been used as a low-calorie sweetener and is being developed as a therapeutic agent for diabetes, hypertension, myocardial diseases, and microbial infections. Despite the common use of its leaves and stem, the bioavailability of the components present in S. rebaudiana flowers, when used as ingredients of cosmetics, has not been well investigated. Herein, we investigated the antioxidative and antimelanogenic effects of an aqueous extract of S. rebaudiana flowers (Stevia-F). Total flavonoid and phenolic content in Stevia-F were determined to be 8.64 ± 0.23 ㎎ of quercetin equivalents/100 g and 631.5 ± 2.01 ㎎ of gallic acid equivalents/100 g, respectively. The IC50 values of Stevia-F for reducing power, and 2,2-diphenyl-1-picryl-hydrazyl-hydrate radical, hydrogen peroxide, and nitric oxide scavenging activities were 5541.96, 131.39, 466.34, and 10.44 ㎍/mL, respectively. Stevia-F showed inhibitory effects on the tyrosinase (IC50 = 134.74 ㎍/mL) and α-glucosidase (IC50 = 114.81 ㎍/mL) activities. No significant cytotoxicity of Stevia-F was observed in B16F10 cells, treated with up to 100 ㎍/mL of the extract for 24 and 48 h (p > 0.05). Stevia-F (1–100 ㎍/mL) suppressed α-melanocyte stimulating hormone-induced melanin production in B16F10 cells (p < 0.05) and also inhibited the cellular tyrosinase activity (p < 0.05). Overall, our results show that Stevia-F possesses potential for inhibiting tyrosinase and α-glucosidase activities and has significant antioxidant capacity. The antimelanogenic potential of Stevia-F should extend the usage of S. rebaudiana flowers in the development of skinwhitening products.

Angelica tenuissima, also known as Ligusticum tenuissimum, is classified as a food-related plant and has been used as traditional medicines treating headache and anemia in Asia. However, its anti-melanogenic effect has not been reported in detail. When the extract of Angelica tenuissima (ATE) was prepared by the extraction with 70% EtOH at 80°C (final yield = 22%), the contents of decursin and Z-ligustilide in ATE were determined 0.06% and 8.43%, respectively. Total flavonoid and phenolic content in mg ATE were 5.52±0.07 ㎍ quercetin equivalents and 237.27±13.24 ㎍ gallic acid equivalents, respectively. Antioxidant capacity of ATE determined by DPPH and ABTS assay was increased with a dose dependent manner up to 1000 ㎍/㎖. The amount of melanin synthesis followed by α-melanocyte stimulating hormone on B16F10 cells were significantly reduced in the presence of ATE (250 to 1000 ㎍/㎖, p<0.05). ATE (125 to 1000 ㎍/㎖, p<0.05) suppressed the tyrosinase activity but did not show any significant effect on α-glucosidase activity at the same condition. Taken together, ATE possesses tyrosinase inhibitory potential with significant antioxidant capacities. These effects of ATE might be involved in suppression of melanin synthesis, at least, in B16F10 cells. The anti-melanogenic potential of ATE will provide an insight into developing a new skin whitening product.